Patent Publication Number: US-11657587-B2

Title: Intelligently placing labels

Description:
INCORPORATION BY REFERENCE DISCLAIMER 
     Each of the following applications are hereby incorporated by reference: application Ser. No. 15/186,406 filed on Jun. 17, 2016; application Ser. No. 13/907,855 filed on Jun. 1, 2013. The Applicant hereby rescinds any disclaimer of claim scope in the parent application or the prosecution history thereof and advises the USPTO that the claims in this application may be broader than any claim in the parent application. 
     BACKGROUND 
     Many map-based applications are available today are designed for a variety of different devices (e.g., desktops, laptops, tablet devices, smartphones, handheld global positioning system (GPS) receivers, etc.) and for various different purposes (e.g., navigation, browsing, sports, etc.). Most of these applications generate displays of a map based on map data that describes the relative location of streets, highways, points of interest, etc. in the map. 
     Some map-based applications provide different types of views of the map and allow to select a type of view for the application to use to display the map. Examples of such types of views include a map view, a satellite view, a hybrid view, etc. For some or all of the different types of views of the map, a number of map-based applications provide a two-dimensional (2D) viewing mode, a three-dimensional (3D) viewing mode, or both viewing modes. 
     BRIEF SUMMARY 
     Some embodiments of the invention provide a novel mapping application renders views of a map (also referred to as a map view) and intelligently places and/or renders map labels for map elements and/or constructs in the map. In some embodiments, the mapping application renders such map views when the mapping application is in a standard-viewing mode or a hybrid-viewing mode. The map labels of some embodiments includes road path indicators, road labels, road direction indicators, points of interest (POI) indicators, POI labels, city labels, city indicators, state labels, continent labels, body of water labels, etc. 
     In some embodiments, the mapping application includes many features to intelligently place and/or render map labels for views of the map. One feature of the mapping application of some embodiments involves preventing map labels from appearing upside down or in an upside down like orientation when rendering the map labels. For instance, when a user rotates the map view, the mapping application also rotates certain types of map labels (e.g., road labels) along with the map. As such map labels rotate towards an upside down orientation, the mapping application flips the map labels so that the map labels appear right side up. 
     Another feature that the mapping application of some embodiments provides involves rendering road labels so that no two map labels collide with each other nor overlap each another. In this manner, the mapping application prevents map labels to obscure other map labels, confusion as to the map elements and/or constructs to which map labels are associated, map labels that are difficult to read or are illegible, etc. 
     The preceding Summary is intended to serve as a brief introduction to some embodiments of the invention. It is not meant to be an introduction or overview of all inventive subject matter disclosed in this document. The Detailed Description that follows and the Drawings that are referred to in the Detailed Description will further describe the embodiments described in the Summary as well as other embodiments. Accordingly, to understand all the embodiments described by this document, a full review of the Summary, Detailed Description and the Drawings is needed. Moreover, the claimed subject matters are not to be limited by the illustrative details in the Summary, Detailed Description and the Drawing, but rather are to be defined by the appended claims, because the claimed subject matters can be embodied in other specific forms without departing from the spirit of the subject matters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the invention are set forth in the appended claims, However, for purposes of explanation, several embodiments of the invention are set forth in the following figures. 
         FIG.  1    conceptually illustrates a mapping application of some embodiments rendering map labels when rotating map labels. 
         FIG.  2    conceptually illustrates a mapping application of some embodiments rendering map labels when map labels collide. 
         FIG.  3    conceptually illustrates an overall process of some embodiments for rendering map labels for a map view. 
         FIG.  4    conceptually illustrates a process of some embodiments for processing roads for map labels in a 3D map. 
         FIG.  5    conceptually illustrates map tiles for roads in a map according to some embodiments of the invention. 
         FIG.  6    conceptually illustrates a road network assembled from the map tiles illustrated in  FIG.  5    according to some embodiments of the invention. 
         FIG.  7    conceptually illustrates a process of some embodiments for determining a layout for map labels in a 3D map. 
         FIG.  8    conceptually illustrates an example of glyph layout for a road name according to some embodiments of the invention. 
         FIG.  9    conceptually illustrates a process of some embodiments for determining collisions between map labels. 
         FIG.  10    conceptually illustrates an example of bounding shapes used for detecting collisions with the glyph layout illustrated in  FIG.  8    according to some embodiments of the invention. 
         FIGS.  11 - 14    conceptually illustrate bounding shapes for different types of map labels that are used for detecting collisions according to some embodiments of the invention. 
         FIGS.  15 - 17    conceptually illustrate several examples of determining collisions based on the bound shapes illustrated in  FIG.  10    according to some embodiments of the invention. 
         FIG.  18    conceptually illustrates a process of some embodiments for determining that map labels are occluded. 
         FIG.  19    conceptually illustrates examples of occluded map labels in a map view of a 3D map. 
         FIG.  20    conceptually illustrates a process for determining the layout of road labels to follow the slope of the roads to which the road labels are associated. 
         FIG.  21    conceptually illustrates an example determining a slope of a road on which to place of a road label. 
         FIG.  22    conceptually illustrates an example of a road label placed on a slope of a road according to some embodiments of the invention. 
         FIG.  23    conceptually illustrates a process of some embodiments for rendering map labels for a map view. 
         FIG.  24    conceptually illustrates a process of some embodiments for rendering map labels based on different adjustments to a view of a map. 
         FIG.  25    conceptually illustrates a mapping application of some embodiments rendering different styles of map labels and/or different map labels based on different zoom levels from which a map is viewed. 
         FIG.  26    conceptually illustrates the mapping application of some embodiments rendering map labels when rotating a map. 
         FIG.  27    conceptually illustrates the mapping application of some embodiments rendering POI banner map labels when rotating a map. 
         FIG.  28    is an example of an architecture of a mobile computing device. 
         FIG.  29    conceptually illustrates an example of an electronic system with which some embodiments of the invention are implemented. 
         FIG.  30    a map service operating environment according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of the invention, numerous details, examples, and embodiments of the invention are set forth and described. However, it will be clear and apparent to one of ordinary skill in the art that the invention is not limited to the embodiments set forth and that the invention may be practiced without some of the specific details and examples discussed. 
     Some embodiments of the invention provide a novel mapping application renders views of a map and intelligently places and/or renders map labels for map elements and/or constructs in the map. In some embodiments, the mapping application renders such map views when the mapping application is in a standard-viewing mode or a hybrid-viewing mode. The map labels of some embodiments includes road path indicators, road labels, road direction indicators, points of interest (POI) indicators, POI labels, city labels, city indicators, state labels, continent labels, body of water labels, etc. 
     In some embodiments, the mapping application includes many features to intelligently place and/or render map labels for views of the map. One feature of the mapping application of some embodiments involves preventing map labels from appearing upside down or in an upside down like orientation when rendering the map labels. For instance, when a user rotates the map view, the mapping application also rotates certain types of map labels (e.g., road labels) along with the map. As such map labels rotate towards an upside down orientation, the mapping application flips the map labels so that the map labels appear right side up. 
       FIG.  1    conceptually illustrates a mapping application of some embodiments rendering map labels when rotating map labels. in particular,  FIG.  1    illustrates a graphical user interface (GUI)  100  of the mapping application of some embodiments operating on a device (e.g., a mobile device, a table computing device, etc.) at four different stages  105 - 120  of rotating a view of a map. 
     The first stage  105  shows the GUI  100  displaying a view of the map. In some embodiments, map view is a view of a 2D map while, in other embodiments, or the map view is a top-down view of a 3D map. As shown, the map view includes several roads and three road labels indicating the names of roads (“Elm Ave”, “Woodland St”, and “Oak Ave” in this example) that the mapping application overlays on the corresponding roads. 
     Different embodiments of the mapping application render different types of map labels using different techniques. For instance, the mapping application of some embodiments renders map views by superimposing 2D map labels (e.g., road labels, POI labels, POI labels, etc.) over rendered map views of the map. That is, in some such embodiments, the mapping application renders a map view of the map and then adds 2D map labels to the rendered map view by overlaying the 2D map labels onto the map view. 
     For 3D maps, the mapping application in some embodiments adds polygons that represent map labels (e.g., road path indicators) to the 3D map and renders map views of the 3D map with the added polygons. In other words, in some such embodiments, the mapping application adds map labels to the 3D map before the mapping application renders map views of the 3D map. In some embodiments, the map labels are part of the 3D map (as opposed to adding the map labels to the 3D map) and the mapping application renders the map labels that are to be displayed in the map view. For map labels that are not to be rendered in the map view, the mapping application of some such embodiments ignores such map labels that the mapping application rendering in the map view of the 3D map. 
     The second stage  110  illustrates a user performing a rotate operation in order to rotate the view of the map. In this example, the user is providing a multi-touch gesture by placing two fingers on a touchscreen of the device on which the mapping application is operating and rotating the two fingers in a counter-clockwise direction about a location on the touchscreen (e.g., a midpoint between an initial pair of points where the two fingers touch the touchscreen) in order to rotate the map view in a counter-clockwise direction. 
     When the mapping application receives input (a multi-touch gesture provided through the touchscreen of the device in this example) to rotate the map view, the mapping application of some embodiments rotates the map view along with the road labels in the map view. As illustrated in the second stage  110 , the mapping application rotates the road labels “Elm Ave”, “Woodland St”, and “Oak Ave” in a counter-clockwise direction about the center of the road labels. 
     In some embodiments, while the mapping application rotates the map view, the mapping application flips a particular road label right side up along a horizontal axis of the particular road label when (1) the particular road label rotates towards an upside down orientation with respect to the GUI  100  and (2) an angle formed by a vector along the particular road label and a vertical axis of the GUI  100  passes a threshold angle (e.g., 10 degrees, 15 degrees, 25 degrees, etc.). The mapping application of some embodiments flips the particular road label right side up by cross fading the particular road label and a right side up version of the particular road label. Specifically, the mapping application of some such embodiments fades out the particular road label that is increasingly rotating towards the upside down orientation while fading in the right side up version of the particular road label. In some embodiments, the mapping application uses additional and/or different techniques to transition from displaying an upside down road label to displaying a right side up version of the road label. 
     The third stage  115  illustrates the GUI  100  after the mapping application has flipped several road labels illustrated in the first and second stages  105  and  110 . As shown, the mapping application in this example has flipped the road labels “Woodland St” and “Oak Ave” as a result of the rotate operation performed by the user in the second stage  110 . In addition, the third stage  115  shows the user continuing to perform performing the rotate operation on the map view. 
     The fourth stage  120  shows the GUI  100  after the user has completed the rotate operation on the map view. As illustrated, the road labels “Woodland. St” and “Oak Ave” are rotate further counter-clockwise compared the third stage  115 . Additionally, the fourth stage  120  illustrates that the road label “Elm Ave” has been rotated out of view. 
     Another feature that the mapping application of some embodiments provides involves rendering road labels so that no two map labels collide with each other nor overlap each another. in this manner, the mapping application prevents map labels to obscure other map labels, confusion as to the map elements and/or constructs to which map labels are associated, map labels that are difficult to read or are illegible, etc. 
       FIG.  2    conceptually illustrates a mapping application of some embodiments rendering map labels when map labels collide. Specifically,  FIG.  2    illustrates the GUI  100  of the mapping application of some embodiments operating on a device (e.g., a mobile device, a table computing device, etc.) at four different stages  205 - 220  of manipulating the view of a map. 
     The first stage  205  is similar to the first stage  105  described above by reference to  FIG.  1   . That is, the first stage  205  shows a map view that includes several roads and the road labels “Elm Ave”, “Woodland St”, and “Oak Ave” that the mapping application overlays on the corresponding roads. In addition, the map view in the first stage  205  includes a POI map label, In some embodiments, a POI map label includes two components: a POI indicator  225  for indicating the location of the POI on the map and a POI label  230  that indicates the name of the POI (“#1 Hamburgers” in this example). 
     The second stage  210  shows a user performing a rotate operation in order to rotate the view of the map. The user for this example is providing a multi-touch gesture by placing two fingers on a touchscreen of the device on which the mapping application is operating and rotating the two fingers in a clockwise direction about a location on the touchscreen (e.g., a midpoint between an initial pair of points where the two fingers touch the touchscreen) in order to rotate the map view in a clockwise direction. 
     When the mapping application receives input (a multi-touch gesture provided through the touchscreen of the device in this example) to rotate the map view, the mapping application of some embodiments rotates the map view along with the road labels in the map view. As shown in the second stage  210 , the mapping application rotates the road labels “Elm Ave”, “Woodland St”, and “Oak Ave” in a clockwise direction about the center of the road labels. The second stage  210  also illustrates that the POI label “#1 Hamburger” is about to collide with the road label “Woodland St”. 
     If the mapping application of some embodiments manipulates the map view, the mapping application detects whether any map labels collide or overlap each other in the new map view. When the mapping application detects a set of map labels colliding or overlapping as a result of the rotation of the map view, the mapping application in some embodiments determines one of the map labels in the set of map labels to be rendered in the map view and ignores the remaining map labels in the set of overlapping map labels. 
     In some embodiments, the mapping application determines the map label in the set of overlapping map labels to render based on a style sheet that specifies a map label to be rendered from a set of colliding map labels. Different embodiments use different criteria to specify the map label to be rendered from the set of colliding map labels. For example, in some embodiments, the style sheet specifies the map label to be rendered based on the type of map labels (e.g., road labels are to be rendered when road labels collide with POI labels and/or POI indicators, city labels are to be rendered when city labels collide with road labels, state labels are to be rendered when state labels collide with city labels, etc.) selected when in the set of colliding map labels. Alternatively, or in conjunction, the style sheet of some embodiments specifies the same or similar type of map labels according to a defined hierarchy. For instance, when road labels collide, the style sheet of some such embodiments specifies to select highways, then expressways, then arterial roads, then collector roads, then back roads, etc. When map label at the same level of the defined hierarchy collide (e.g., highway road labels colliding, expressway road labels colliding, arterial road labels colliding, collector road labels colliding, back road labels colliding, etc.) the mapping application of some embodiments randomly selects a map label to be rendered. 
     The third stage  215  illustrates the GUI  100  after the user has completed the rotate operation on the map view. For this example, the mapping application detected that the POI label “#1 Hamburger” was colliding with the road label “Woodland St”, selected the road label “Woodland St” to be rendered, and ignored the POI label “#1 Hamburger”. Since the road label “Woodland. St” does not collide with the POI indicator  225 , the mapping application still renders the POI indicator in the map view, as shown in the third stage  215 . The mapping application in this example did not detect the road labels “Elm Ave” and “Oak Ave” colliding with any other map labels and, thus, continues to render those road labels. 
     Additionally, the third stage  215  illustrates the user performing a zoom operation in order to zoom out from the view of the map (i.e., to view the map from a farther distance). In this example, the user is providing a multi-touch gesture by placing two fingers on a touchscreen of the device and moving the two fingers in towards each other in order to zoom out from the map view. 
     As explained above, when the mapping application of some embodiments manipulates the map view, the mapping application detects whether any map labels collide or overlap each other in the new map view. The third stage  215  illustrates an example of map labels that collide as a result of a zoom operation (as opposed to a rotate operation shown in the second stage  210 ). If the mapping application detects a set of map labels colliding or overlapping as a result of the zooming out from the map view, in some embodiments the mapping application determines one of the map labels in the set of map labels to be rendered in the map view and ignores the remaining map labels in the set of overlapping map labels in a similar fashion as that described above by reference to the second stage  210 . 
     The fourth stage  220  illustrates the GUI  100  after the user has completed the zoom operation on the map view. The mapping application in this example detected that the road label “Elm Ave” was colliding with the road label “Woodland St”, selected the road label “Woodland St” to be rendered, and ignored the road label “Elm Ave”. Also, the mapping application in this example did not detect the road label “Oak Ave” colliding with any other map labels and, therefore, continues to render that road label. 
     In some embodiments, the mapping application includes several different viewing modes that a user may select for viewing a map. For instance, the mapping application of some embodiments provides a standard-viewing mode, a satellite-viewing mode, and a hybrid-viewing mode for viewing the map. Other embodiments may provide additional and/or different viewing modes. 
     When the mapping application is in a satellite-viewing mode, the mapping application of some embodiments renders map views using camera-captured images (CCIs). In some embodiments, CDs are images of the real world captured by real cameras operated by humans and/or machines (as opposed to a virtual camera that is used for rendering views of a 3D model). CCIs include images captured by real cameras on satellites, fly-by captured images (e.g., images captured by real cameras on airplanes, space shuttles, helicopters, balloons, and/or any other device used for aerial photography), drive-by captured images (e.g., images captured by real cameras on cars, trucks, motorcycles, buses, bicycles, trains, and/or any other type of vehicle that operates on land), etc. CCIs are referred to as real world captured images in some embodiments. The mapping application of some embodiments renders satellite map views by texture mapping CCIs to the map, map elements, and/or map constructs in the 3D map. 
     In some embodiments, a map service generates 3D model of a map that represents the real world based on geographical data collected from the real world. Some or all of the 3D primitives (e.g., points, lines, polygons, surfaces, etc.) of the 3D model of the map include location data that maps the to the corresponding location in the real world. In some embodiments, when a capturing device (e.g., a real camera) captures CCIs, the capturing device also records the location (e.g., UPS data) and position of the capturing device. 
     Based on information regarding the location and position of a capturing device used to capture a particular CCI, the map service of some embodiments identifies positions in the 3D model of the map to which pixels and/or groups of pixels in the particular CCI correlate. In some embodiments, the map service then maps the particular CCI to the 3D model of the map based on the identified positions. Such mapping, in some embodiments, is referred to as texture mapping. In some embodiments, the map service manipulates (e.g., rotated, translated, scaled, etc.) the particular CCI to better align the elements in the particular CCI with corresponding elements in the 3D model of the map. 
     In some embodiments, the mapping application renders map views using the 3D model of the map textured with CCIs by accessing (e.g., through the Internet) the map service described above and retrieving data (e.g., stored as satellite map tiles) representing a portion of the 3D model of the map from which the mapping application renders the map views. The data includes in some embodiments polygons that represent the map elements and/or map constructs in the portion of the 3D model and the corresponding CCIs with which the mapping application texture maps to the polygons. Such rendering is referred to in some embodiments as stereographic rendering using on CCIs. In some embodiments, the mapping application renders such map views of the 3D model of the map when the mapping application is in a satellite-viewing mode and rendering 3D satellite map views described in this application. Details of generating 3D maps with CCIs are described in PCT Application PCT/EP2011/054155, entitled “3D Streets.” PCT Application PCT/EP2011/054155 is incorporated herein by reference. 
     In some embodiments, when the mapping application is in a hybrid-viewing mode, the mapping application renders map views using CCIs and map labels for map elements and/or constructs in the map view. For instance, the mapping application of some embodiments uses the same or a similar technique described above for rendering map views in the satellite-viewing mode (i.e., texture mapping CCIs to the map, map elements, and/or map constructs in the 3D map) and augments such map views with map labels. That is, the mapping application of some such embodiments texture maps CCIs to the map, map elements, and/or map constructs in the 3D map and adds map labels to the map view in order to annotate some or all of the map elements (streets, highways, POIs, cities, states, countries, continents, bodies of water, etc.) in the map view. 
     When the mapping application is in a standard-viewing mode, the mapping application of some embodiments renders map views using non-CCIs (e.g., user-generated textures/images, machine-generated textures/images, etc.) and map labels for map elements and/or constructs in the map view. In other words, the mapping application of some such embodiments renders map views without using any CCIs for the standard-viewing mode adds map labels to the map view in order to annotate some or all of the map elements in the map view. 
       FIG.  3    conceptually illustrates an overall process  300  of some embodiments for rendering map labels for a map view. In some embodiments, the mapping applications described above and below by reference to  FIGS.  1 ,  2 ,  19 ,  22 , and  25    performs the process  300  when rendering map labels for a map view. The mapping application of some embodiments renders map labels for a map view when the mapping application is in a hybrid-viewing mode or a standard-viewing mode. 
     The process  300  starts by retrieving (at  305 ) map tiles to process roads in a 3D map so that the roads can be later annotated with map labels. In some embodiments, the process  300  retrieves the map tiles from a map service, such as the map service described above. The map tiles in some embodiments provide road data that describes the roads in the requested portion of the map. Such map tiles may be referred to as road tiles in this application. In some embodiments, 3D data (e.g., polygon data, mesh data, etc.) that describes the map elements and/or map constructs (e.g., buildings, foliage, bodies of water, etc.) in the 3D map are stored in a set of map tiles separate from the road tiles. The road tiles of some embodiments include a portion of the 3D data that describes the map elements and/or map constructs in 3D map. For instance, in some such embodiments, the map tiles of some embodiments that include the road. data for the 3D map also include data for land in the 3D map and data for the remaining map elements and/or map constructs in the 3D map are stored in separate map tiles. Still, in some embodiments, the road data for the 3D map and the 3D data that describes the map elements and/or map constructs in 3D map are stored in a single set of map tiles. 
     In some embodiments, the retrieved map tiles for processing roads provides data for a range or band of zoom levels (i.e., distances from the 3D map). For example, the retrieved map tiles of some embodiments might be specified for use for zoom levels  11 - 15 , zoom levels  16 - 20 , or any other defined range of zoom levels. 
     The process  300  of some embodiments performs a variety of operations to process the roads using road data in the map tiles including assembling the roads, identifying road segments, determining styling for map labels, determining sizes of map labels, and identifying candidate positions along the road segments at which to potentially place map labels, among other operations. Details of processing roads is described below by reference to  FIGS.  4 - 6   . 
     In some embodiments, the process  300  performs  305  as part of a tile loading processing that the process  300  or another process performs. The tile loading process of some such embodiments is for processing and loading tiles of the portion of the 3D map that is used to render a map view. 
     Next, the process  300  then determines (at  310 ) a layout of map labels for the 3D map. The process  300  of some embodiments determines and generates the layout of map labels for the 3D map based on a virtual camera that is used to identify a position in the 3D map from which to render a view of the 3D map. In some embodiments, a virtual camera is a conceptualization of the position in the 3D map from which the mapping application renders a map view of the 3D map. 
     In some embodiments, the process  300  determines the layout by selecting positions at which to place labels based on the identified candidate positions and the position and orientation of the virtual camera. As part of determining the layout, the process  300  of some embodiments determines the position and orientation of each character (i.e., a glyph) for map labels of roads that contain strings (e.g., road names). Details of determining the layout of map labels for the 3D map is described below by reference to  FIGS.  7 - 18   . 
     Finally, the process  300  renders (at  315 ) map labels for the 3D map. The process  300  of different embodiments renders map labels using different techniques. For instance, in some embodiments, the process  300  renders map labels for the 3D map by superimposing 2D map labels (e.g., road labels, POI labels, POI labels, etc.) over rendered map views of the map. That is, in some such embodiments, the mapping application renders a map view of the map and then adds 2D map labels to the rendered map view by overlaying the 2D map labels onto the map view. 
     Alternatively, or in conjunction, the process  300  of some embodiments renders map labels for the 3D map by adding polygons that represent map labels (e.g., road path indicators) to the 3D map and rendering map views of the 3D map with the added polygons. In other words, in some such embodiments, the process  300  adds map labels to the 3D map before the process  300  renders map views of the 3D map. In some embodiments, the map labels are part of the 3D map (as opposed to adding the map labels to the 3D map) and the process  300  renders the map labels that are to be displayed in the map view. For map labels that are not to be rendered in the map view, the process  300  of some such embodiments ignores such map labels when the process  300  is rendering map labels for the 3D map. 
     Several more detailed embodiments of the invention are described in the sections below. Section I conceptually describes details of processing roads for map labels according to some embodiments. Next, Section II conceptually describes determining layouts of map labels according to some embodiments of the invention. Section III describes rendering map labels for map views according to some embodiments of the invention. Next, Section IV describes example electronic systems with which some embodiments of the invention are implemented. Finally, Section V describes a map service operating environment in which some embodiments of the invention operate. 
     II. Processing Roads for Map Labels 
     As mentioned above, the mapping application of some embodiments processes roads for map labels in a map in order to render the map labels in a view of the map.  FIG.  4    conceptually illustrates a process  400  of some embodiments for processing roads for map labels in a 3D map. In some embodiments, the mapping application described above and below by reference to  FIGS.  1 ,  2 ,  19 ,  22 , and  25    performs the process  400 . The mapping application of some embodiments performs the process  400  as part of operation  305  described above by reference to  FIG.  3   . 
     The process  400  will be described by reference to  FIGS.  5  and  6   .  FIG.  5    conceptually illustrates map tiles  505 - 530  for a map according to some embodiments of the invention.  FIG.  6    conceptually illustrates a road network  600  assembled from the map tiles illustrated in  FIG.  5    according to some embodiments of the invention. 
     As shown, the process  400  begins by assembling (at  405 ) roads for a map in order to create a road network for the map. In some embodiments, the process  400  assembles the roads based on road data included in map tiles retrieved from a map service. To assemble the roads in the map, in some embodiments, the process  400  identifies road segments in the same and/or different map tiles that are specified as part of the same road and joins the identified road segments to form a single road segment. The process  400  of some embodiments identifies road segments as belonging to the same road based on attributes of the road segments (e.g., road names, road route numbers or shield names, etc.). In some embodiments the road segment attributes are stored as metadata in the corresponding map tiles. For instance, in some embodiments, the process  400  identifies road segments in map tiles as part of the same road when the road segments have the same name. 
     In some embodiments, a road is might be referred to by a name as well as a route number. For example, a highway might be referred to as “Santa Maria Highway” and highway “13”, an expressway might be referred to as “Laurel Expressway” and route “17”. etc. Alternatively to, or in conjunction with matching road names, the process  400  identifies road segments in different map tiles as part of the same road when the road segments have the same route number. 
     Referring to  FIG.  5    as an example, the map tiles  505 - 530  are for assembling roads for a portion of a map. The assembled roads form a road network for the portion of the map. In this example, the map tiles  505 - 530  include road data that describe road segments  540 - 578  that are used to create the road network for the portion of the map. As shown, the map tile  505  includes the road segments  540 - 544 , the map tile  510  includes the road segments  546 - 554 , the map tile  515  includes the road segments  556 - 560 , the map tile  520  includes the road segments  564 - 566 , the map tile  525  includes the road segments  568 - 572 , and the map tile  530  includes the road segments  574 - 578 . 
     Continuing with the example,  FIG.  6    illustrates the road network  600 , which is assembled from the road segments  540 - 578  shown in  FIG.  5   . For this example, the road segments  540 - 578  in  FIG.  5    were joined together in the same or similar manner described above by reference to operation  405  of  FIG.  4    to form the road network  600 . 
     As illustrated, the road segments  540 ,  556 , and  568  were joined to form the road segment  605 , the road segments  544 ,  560 , and  570  were joined to form the road segment  615 , the road segments  546  and  548  were joined to form the road segment  620 , the road segments  550 ,  564 , and  576  were joined to form the road segment  625 , the road segments  554 ,  566 , and  578  were joined to form the road segment  635 , the road segments  558  and  562  were joined to form the road segment  640 , and the road segments  572  and  574  were joined to form the road segment  645 . 
     Once the process  400  joins the road segments to form a single road segment, the process  400  aggregates the attributes of the road segments (e.g., road name, road route number or shield name, a one-way road, a two-way road, styling for the road segments, etc.) and associates the single road segment with the aggregated attributes. 
     Next, the process  400  identifies (at  410 ) locations along roads in the road network at which not to place map labels. In some embodiments, the process  400  identifies such locations by iterating through each road segment in the road network and detecting junctions, intersections, and sharp bends along the road segment. The process  400  ignores these identified locations when performing  425 , which is described below. 
     In some embodiments, a road is represented by an ordered chain of points and line segments that link each point to the next point, which forms a sequence of line segments. To identify sharp bends (at which not to place map labels) in a road represented in such a manner, the process  400  of some embodiments compares an angle formed by a pair of adjacent line segments in the road representation with a defined threshold angle (e.g., 10 degrees, 20 degrees, 35 degrees, etc.). if the angle formed by the pair of adjacent line segments passes the threshold angle, the process  400  determines that a sharp bend exists at the point between the pair of line segments and identifies the point as a location at which not to place map labels. In some embodiments, the process  400  analyzes every set of three consecutive points along the roads in the road network in order to identify sharp bends in the roads at which not to place map labels. 
     In some embodiments, the process  400  uses a different approach to identify sharp bends in a road that is represented by an ordered chain of points and line segments that link each point to the next point. When the total length of a pair of adjacent line segments is less than a defined threshold length, the process  400  of some embodiments identifies a short chain of consecutive line segments that includes the pair of adjacent line segments and has a total length that is greater than or equal to the threshold length. 
     The process  400  identifies sharp bends in such a chain of line segments comparing the defined threshold angle (or a different defined threshold angle) with an angle formed by a pair of line segments that each start at different ends of the chain and terminates at a common point at or near the middle of the chain of line segments. If the angle formed by the pair of line segments passes the threshold angle, the process  400  determines that a sharp bend exists at the point between the pair of line segments and identifies the point as a location at which not to place map labels. In some embodiments, the process  400  analyzes every set of three consecutive points along the roads in the road network in order to identify sharp bends in the roads at which not to place map labels. 
     As an example,  FIG.  6    additionally illustrates positions along roads in the road network  600  at which not to place map labels, in this example, locations in the road network  600  that have intersecting roads are marked with Xs to indicate that map labels are not to be placed at these positions. 
     Returning to  FIG.  4   , the process  400  then determines (at  415 ) the styling of labels in the map. In some embodiments, the process  400  determines the styling of the map labels based on localization factors, such as language settings, time zone settings, etc., that indicate the locality of the device on which the mapping application is running. Alternatively, or in conjunction with the locality of the device, the process  400  of some embodiments determines the styling of the map labels based on a style sheet that specifies styling of the map labels. In some embodiments, the style sheet specifies styling according to the type of map element and/or map construct (e.g., a freeway, a suburban street, a city, a state, a continent, etc.) for which map labels are rendered, the type of device (e.g., a smartphone, a table computing device, a desktop computer, a laptop computer, etc.) for which the mapping application is operating, etc. The styling of the map labels specifies in some embodiments the type of font, the color, and the size of the characters to use for the different map labels. 
     Next, the process  400  determines (at  420 ) the size of map labels. The process  400  of some embodiments determines the size of map labels by determining the size of each character (e.g., the dimensions of each character in terms of pixels or pica) for strings in map labels and the size of the strings (e.g., the height, width, and/or length of the strings in terms of pixels or pica). In some embodiments, the process  400  uses a text system, such as a system level text code that provides the width of strings based on a specified font, size, and road classification e.g., highways, expressways, arterial roads, collector roads, back roads, etc.). 
     Finally, the process  400  identifies (at  425 ) candidate positions along roads in the road network for placing map labels. In some embodiments, when the process  400  identifies the candidate positions, the process  400  ignores the locations identified at  410 . That is, the process  400  in some such embodiments does not consider locations along roads that have junctions, intersections, and/or sharp bends. 
     In some embodiments, the process  400  identifies candidate positions by analyzing every section of road in the road network that does not have any junctions, intersections, or sharp bends. For such a particular road section, the process  400  determines whether the particular road section is specified as a one-way road. If the particular road section is a one-way road and the length of the particular road section is shorter than a threshold length, the process  400  places a map label indicating that the particular road section is a one-way road (e.g., a one-way arrow). Otherwise, the process  400  places a map label indicating the road name or route number or shield name at the midpoint of the particular road section. 
     The process  400  continues to iteratively place map labels indicating the road name or route number or shield name at defined increments from the midpoint of the particular road section towards each end of the particular road section. When the length of the particular road section from a position at which a map label was last placed to the end of the particular road section closest to the position is shorter than a defined length, the process  400  stops placing map labels along the particular road section. In some embodiments, if the particular road section is specified as a one-way road, the process  400  places map labels indicating that the particular road section is a one-way road (e.g., a one-way arrow) between the map labels that were last placed and the end of the particular road section closest to the map labels. 
     Referring to  FIG.  6    as an example, this figure also conceptually illustrates candidate positions along roads in the road network  600  for placing map labels. The candidate positions in this example are indicated by circles along roads in the road network  600 . As shown, candidate positions are not placed at any of the positions identified at  610 , which are indicated by Xs in  FIG.  6   . 
     II. Determining Layouts for Map Labels 
     As noted above, in some embodiments, when the mapping application determines a layout for map labels, the mapping application uses a virtual camera for identifying a position in a 3D map from which to render a view of the 3D map and selects positions at which to place labels based on candidate positions identified according to the techniques described in the previous Section I and the position and orientation of the virtual camera. 
       FIG.  7    conceptually illustrates a process  700  of some embodiments for determining a layout for map labels in a 3D map. The mapping application described above and below by reference to  FIGS.  1 ,  2 ,  19 ,  22 , and  25    performs in some embodiments the process  700 . in some embodiments, the mapping application performs the process  700  as part of operation  310  described above by reference to  FIG.  3   .  FIG.  7    will be describe by reference to  FIG.  8   , which conceptually illustrates an example of glyph layout for a road name according to some embodiments of the invention. 
     As shown, the process  700  starts by selecting (at  705 ) label positions for map labels in the layout. In some embodiments, the process  700  selects the label positions from the candidate label positions identified at operation  425  described above by reference to  FIG.  4   . The process  700  of some embodiments selects the labels positions based on (1) the position and orientation of a virtual camera that identifies a position in a 3D map from which to render a view of the map and (2) the label size determined at operation  420  described above by reference to  FIG.  4   . For instance, the process  700  uses the position of the virtual camera to determine the zoom level (i.e., the distance from the virtual camera to the 3D map along the z-axis of the 3D map) and the determined label sizes of strings in map labels in some embodiments. 
     Next, the process  700  determines (at  710 ) visibility of map labels based on the position and orientation of the virtual camera. In some embodiments, the process  700  ignores map labels of map elements and/or map constructs with distances from the virtual camera that are not within a threshold range of distances since such map elements and/or map constructs are too far or close to be visible. The threshold range of distance is specified in a style sheet in some embodiments. In some embodiments, the style sheet specifies different types of map labels to be rendered for different ranges of zoom levels. For instance, the style sheet of some such embodiments might specify to render shield names for highways at one range of zoom levels, render road names for the highways at a second range of zoom levels, render road names for arterial roads at a third range of zoom levels, render road names for back roads at a fourth range of zoom levels, render city names for cities at a fifth range of zoom levels, etc. 
     The process  700  then determines (at  715 ) glyph layouts for map labels that include strings. In some embodiments, the process  700  determines the glyph layouts by determining the location and manner in which to place each character of the strings. For instance, the process  700  of some embodiments places the glyphs for road names such that the road name follows the curvature of the road to which the road name is associated. Referring to  FIG.  8    as an example, the road name “Washington” is shown following the curvature of a road  805 . That is, each character of the road name “Washington” is placed along the road  805  so that a line that bisects the character is tangent to the road  805  at a point at which the line intersects the road  805 . For other types of map labels, such as POI names, the process  700  lays the string in a horizontal orientation. 
     In some embodiments, the process  700  determines the shape for each character in a string of a map label based on a specified letterform. The letter forms for the characters are derived from texture atlases. In some embodiments, a texture atlas is an image that includes a collection of sub-images. Each sub-image corresponds to a letter rendered according to the specified letterform of the atlas. Instead of rendering the glyphs during the rendering of the map view, the process  700  of some embodiments renders the glyphs when determining the layout of the map labels in order to offload the expensive performance cost of rendering glyphs to this stage and, thus, increase the speed of rendering the map view when it is later rendered. 
     Finally, the process  700  performs (at  720 ) culling operations to prevent from being rendered map labels that may be partially visible or not visible at all and overlapping map labels. In some embodiments, the culling operations that the process  700  performs include detecting map labels that are colliding with each other and map labels that are occluded by map elements and/or map constructs in the map. Details of such operations are described below by reference to  FIGS.  9 - 19   . The process  730  of some embodiments also performs de-duping as part of the culling operations. In some embodiments, de-duping involves identifying map elements and/or map constructs that are specified to be labeled with only one map label. For instance, water ways, such as the English channel, are specified in some embodiments to be labeled with only one map label. In some such embodiments, the process  700  identifies water ways in the map and selects only one position along the water ways to render a map label. 
     A. Collision Detection 
       FIG.  9    conceptually illustrates a process  900  of some embodiments for determining collisions between map labels. In some embodiments, the mapping application described above and below by reference to  FIGS.  1 ,  2 ,  19 ,  22 , and  25    performs the process  900 . The mapping application of some embodiments performs the process  900  as part of operation  720  described above by reference to  FIG.  7   . 
     The process  900  will be described by reference to  FIGS.  10 - 17   .  FIG.  10    conceptually illustrates an example of bounding shapes used for detecting collisions with the glyph layout illustrated in  FIG.  8    according to some embodiments of the invention.  FIGS.  11 - 14    conceptually illustrate bounding shapes for different types of map labels that are used for detecting collisions according to some embodiments of the invention.  FIGS.  15 - 17    conceptually illustrate several examples of determining collisions based on the bound shapes illustrated in  FIG.  10    according to some embodiments of the invention. 
     As shown, the process  900  begins by determining (at  905 ) bounding shapes for map labels in the layout of the map labels. Different embodiments used any number for different bounding shapes for detecting collisions with different map labels. For instance, the process  900  of some embodiments determines circular bounding shapes that encompass each character in a road name and a rectangular bounding shape that encompasses the entire string of the road name. As an example,  FIG.  10    shows two different bounding shapes for detecting collisions with the glyphs (i.e., characters) in the glyph layout of the road name “Washington”. As shown, circular bounding shapes  1010 - 1055  are used as bounding shapes that encompass each character in the string “Washington”, In addition, a rectangular bounding shape  1005  is used as a bounding shape that encompasses the entire string of the road name. 
     For other types of map labels, the process  900  of some embodiments determines different bounding shapes. For instance, the process  900  determines for route numbers or shield names of roads using a circular bounding shapes that encompasses the route number or shield name.  FIG.  11    conceptually illustrates such a bounding shape  1105  for route number “19”, The process  900  uses a similar bounding shape for map labels indicating that a road is a one-way road, such as a circular bounding shape  1305  for a map label of a one-way directional arrow illustrated in  FIG.  12   . 
       FIGS.  13  and  14    show examples of bounding shapes of different POI map labels  1300  and  1400  for which the process  400  of some embodiments determines for detecting collisions with the POI map labels  1300  and  1400 . In particular,  FIG.  13    illustrates a circular bounding shape  1310  that encompasses the POI map label  1300 &#39;s POI indicator, a rectangular bound shape  1315  that encompasses the POI map label  1300 &#39;s POI label, and a rectangular  1305  that encompasses the POI map label  1300 . 
     In some embodiments, the POI label of a POI map label spans several horizontal lines. The process  900  of some such embodiments determines a bounding shape for the string at each horizontal line the POI label. Specifically,  FIG.  14    illustrates a circular bounding shape  1410  that encompasses the POI map label  1400 &#39;s POI indicator, a rectangular bound shape  1415  that encompasses the string on the top line of POI map label  1400 &#39;s POI label, a rectangular bound shape  1420  that encompasses the string on the bottom line of POI map label  1400 &#39;s POI label, and a rectangular  1405  that encompasses the POI map label  1400 . 
     Once determining bounding shapes for map labels in the layout is completed, the process  900  then identifies (at  900 ) a map label in the layout of map labels. In some embodiments, the process  900  identifies a map label in the layout in a left-to-right manner. In other words, the process  900  scans the layout from left-to-right to identify a map label in the layout. The process  900  of some embodiments scans the layout in a top-to-bottom fashion to identify a map label in the layout. Still, in some embodiments, the process  900  uses a combination of scanning the layout left-to-right and top-to-bottom to identify a map label in the layout. 
     Next, the process  900  determines (at  915 ) whether the identified map label collides with another map label in the layout based on the bounding shape(s) determines for the identified map label. For road names with hounding shapes determined in the manner illustrated in  FIG.  10   , the process  900  of some embodiments uses the rectangular bounding shape that encompasses the entire string of the road name for a course, first level collision detection analysis. That is, the process  900  determines whether the bounding shapes of any other map label in the layout touches or intersects with the rectangular bounding shape that encompasses the entire string of the road name. If no collision is detected, the process  900  determines that the identified map label does not collide with any map labels in the layout. 
     If a collision is detected in the course, first level collision detection analysis, the process  900  of some embodiments uses the circular bounding shapes that encompasses the characters in the string of the road name for a finer, second level collision detection analysis. If the process  900  determines that the bounding shape of a map label in the layout touches or intersects with any of the circular bounding shapes that encompass the characters of the road name, the process  900  determines that the identified map label collides with another map label in the layout. Otherwise, the process  900  determines that the identified map label does not collide with any other map label in the layout even though a collision was detected in the course, first level collision detection analysis. 
       FIGS.  15 - 17    conceptually illustrate several examples of determining collisions based on the bound shapes illustrated in  FIG.  10    according to some embodiments of the invention. Specifically,  FIG.  15    illustrates an example of a collision not detected in the course, first level collision detection analysis. As shown in  FIG.  15   , a road name “Main” has circular bounding shapes  1510 - 1525  that encompass the characters of the string “Main” and a rectangular bounding shape  1505  that encompasses the entire string of the road name. In this example, the rectangular bounding shape  1005  of the road name “Washington” does not touch nor intersect with the rectangular bounding shape  1505  of the road name “Main”. Accordingly, the process  900  determines in this example that the road name “Washington” does not collide with the road name “Main. 
       FIG.  16    illustrates an example of a collision detected in the course, first level collision detection analysis, but a collision not detected in the finer, second level collision detection analysis. As illustrated, the rectangular bounding shape  1005  of the road name “Washington” intersects with the rectangular bounding shape  1505  of the road name “Main”. However, none of the circular bounding shapes  1010 - 1055  that encompass the characters of the road name “Washington” touch nor intersect any of the circular bounding shapes  1510 - 1525  that encompass the characters of the road name “Main”. Therefore, the process  900  determines for this example the road name “Washington” does not collide with the road name “Main. 
       FIG.  17    illustrates an example of a collision detected in the course, first level collision detection analysis and in the finer, second level collision detection analysis. As illustrated in  FIG.  17   , the rectangular bounding shape  1005  of the road name “Washington” intersects with the rectangular bounding shape  1505  of the road name “Main”. Additionally, the circular bounding shapes  1010  that encompasses the character “W” in the road name “Washington” intersects with the circular bounding shapes  1525  that encompass the character “N” in the road name “Main”. As such, the process  900  in this example determines that the road name “Washington” collides with the road name “Main. 
     In some embodiments, the mapping application renders a portion of a map label when the portion of the map label does not collide with another map label. As described above by reference to  FIG.  2   , a POI map label in some embodiments includes (1) a POI indicator for indicating the location of the POI and (2) a POI label that indicates the name of the POI. When the POI label collides with another map label, some such embodiments still render the POI indicator if the POI indicator does not collide with any map labels. 
     Referring to  FIG.  13    as an example, the process  900  of some embodiments keeps only the POI indicator in the layout of map labels when the process  900  determines that the rectangular bounding shape  1305  of the POI map label touches or intersects with the bounding shape of a map label in the layout, determines that the rectangular bounding shape  1315  touches or intersects with the bounding shape of a map label in the layout, and that the circular bounding shape  1310  does not touch not intersect with the bounding shapes of any other map labels in the layout. 
     Returning to  FIG.  9   , when the process  900  determines that the identified map label does not collide with any map label in the layout, the process  900  leaves (at  925 ) the identified map label in the layout and continues to  935 . When the process  900  determines that the identified map label collides with another map label in the layout, the process  900  determines (at  920 ) whether to keep the identified map label in the layout. 
     As mentioned above, some embodiments selects a map label from a set of overlapping map labels to render based on a style sheet that specifies a map label to be rendered from a set of colliding map labels. Different embodiments use different criteria to specify the map label to be rendered from the set of colliding map labels. For example, in some embodiments, the style sheet specifies the map label to be rendered based on the type of map labels (e.g., road labels arc to be rendered when road labels collide with POI labels and/or POI indicators, city labels are to be rendered when city labels collide with road labels, state labels are to be rendered when state labels collide with city labels, etc.) selected when in the set of colliding map labels. Alternatively, or in conjunction, the style sheet of some embodiments specifies the same or similar type of map labels according to a defined hierarchy. For instance, when road labels collide, the style sheet of some such embodiments specifies to select highways, then expressways, then arterial roads, then collector roads, then back roads, etc. When map label at the same level of the defined hierarchy collide (e.g., highway road labels colliding, expressway road labels colliding, arterial road labels colliding, collector road labels colliding, back road labels colliding, etc.) the mapping application of some embodiments randomly selects a map label to be rendered. 
     If the process  900  determines to keep the map label in the layout, the process  900  leaves (at  925 ) the map label in the layout and proceeds to  935 . In some embodiments, the process  900  also removes from the layout the map label with which the identified map label was determined to collide. If the process  900  determines to not to keep the map label in the layout, the process  900  removes (at  930 ) the map label from the layout and continues to  935 . 
     Finally, the process  900  determines (at  935 ) whether any map label in the layout is left to process. In some embodiments, the process  900  uses the techniques described above to scan the layout for any map label left to process. When the process  900  determines that a map label in the layout is left to process, the process  900  returns to  910  to continue processing any remaining map labels in the layout. Otherwise, the process  900  ends. 
     B. Occlusion Detection 
       FIG.  18    conceptually illustrates a process  1800  of some embodiments for determining map labels that are occluded. The mapping application of some embodiments described above and below by reference to  FIGS.  1 ,  2 ,  19 , and  22    performs the process  1800  when rendering views of a map from a 3D perspective. In some embodiment, the mapping application performs the process  1800  as part of operation  720  described above by reference to  FIG.  7   . The process  1800  will be described by reference to  FIG.  19   , which conceptually illustrates examples of occluded map labels in a map view of a 3D map. 
     As shown, the process  1800  starts by identifying (at  1805 ) a virtual camera position for the layout of map labels. As noted above, in some embodiments, a virtual camera is a conceptualization of the position in the 3D map from which the mapping application renders a map view of the 3D map. In some embodiments, the process  1800  identifies the virtual camera position by identifying the position and orientation of the virtual camera with respect to the 3D map. 
     Next, the process  1800  identifies (at  1810 ) a map label in the layout of map labels. The process  1800  of some embodiments identifies a map label in the layout in a left-to-right manner. That is, in some such embodiments, the process  1800  scans the layout from left-to-right to identify a map label in the layout. In some embodiments, the process  1800  scans the layout in a top-to-bottom fashion to identify a map label in the layout. Still, the process  1800  of some embodiments uses a combination of scanning the layout left-to-right and top-to-bottom to identify a map label in the layout. 
     The process  1800  then projects (at  1815 ) a line segment in the 3D map for the map label. In some embodiments, the process  1800  projects the line segment in the 3D map from the center of the map label and up along the z-axis of the 3D map, Different embodiments project line segments with different lengths. In some embodiments, the process  1800  projects line segment having a particular length based on a defined length specified in a style sheet. 
     Next, the process  1800  determines (at  1820 ) whether the line segment is occluded based on the identified virtual camera position. In some embodiments, the process  1800  determines that the line segment is occluded when the entire line segment is occluded. In some embodiments, the process  1800  determines that the line segment is occluded when the portion of the line segment that is occluded passes a defined percentage (e.g., 80 percent of the line segment, 90 percent of the line segment, 95 percent of the line segment, etc.) of the entire line segment. 
     As an example,  FIG.  19    conceptually illustrates a portion of a 3D map  1900  at two stages  1905  and  1910  that show map labels occluded when the map is viewed from a 3D perspective. The first stage  1905  illustrates a view of the portion of the 3D map  1900 . Here, the portion of the 3D map  1900  is viewed from a top-down perspective. As shown, the map view includes several roads, two road labels indicating the names of the corresponding roads, three buildings, and two POIs indicated by two POI map labels. 
     The second stage  1910  illustrates the GUI  1900  displaying a view of the map similar to the portion of the map illustrated in the first stage  1905  except the view of the map in the second stage  1910  is from a 3D perspective. The second stage  1910  also shows line segments  1915 - 1930  that are vertically projected in the 3D map. As shown, the line segment  1915  is vertically projected from the center of the POI indicator for “Jane&#39;s Bakery”, the line segment  1920  is vertically projected from the center of the road label “Central Ave”, the line segment  1925  is vertically projected from the center of the road label “Grand Blvd”, and the line segment  1930  is vertically projected from the center of the POI indicator for “Mike&#39;s Pizza”. 
     in this example, the line segments  1915  and  1920  are not occluded by any map elements and/or map constructs from the view of the map illustrated in the second stage  1910 . Therefore, the process  1800  in some embodiments leaves the POI map label for “Jane&#39;s Bakery” and the road label “Central Ave” in the layout of map labels for rendering. The line segments  1925  and  1930  are completely occluded by a building from the view of the map illustrated in the second stage  1910 . Thus, the process  1800  of some embodiments removes the POI map label for “Mike&#39;s Pizza” and the road label “Grand Blvd” from the layout of map labels and are not rendered, as indicated by a greying out of the POI label for “Mike&#39;s Pizza” and the road label “Grand Blvd”. 
     Returning to  FIG.  18   , when the process  11800  determines that the line segment not is occluded, the process  1800  leaves (at  1825 ) the map label in the layout and continues to  1835 . If the process  1800  determines that the line segment is occluded, the process  1800  removes (at  1830 ) the map label from the layout. 
     Finally, the process  1800  determines (at  1835 ) whether any map label in the layout is left to process. In some embodiments, the process  1800  uses the techniques described above to scan the layout for any map label left to process. When the process  1800  determines that a map label in the layout is left to process, the process  1800  returns to  1810  to continue processing any remaining map labels in the layout. Otherwise, the process  1800  ends. 
     C. Road Labels on Slopes 
     As explained above, the mapping application of some embodiments determines the layout of the characters of road labels so that the road label follows the curvature of the road to which the road name is associated. In some embodiments, a road in a 3D map may also slope up or down and in some instances undulate up and down. The mapping application of some embodiments determines the layout of the characters of a road label such that the road label follows the slope and/or undulation of the road to which the map label is associated. 
       FIG.  20    conceptually illustrates a process  2000  for determining the layout of road labels to follow the slope of the roads to which the road labels are associated. In some embodiments, the mapping application described above and below by reference to  FIGS.  1 ,  2 ,  19 ,  22 , and  25    performs the process  2000  when determining the glyph layouts of road labels. The mapping application of some embodiments performs the process  2000  as part of operation  715  described above by reference to  FIG.  7   . The process  2000  will be described by reference to  FIGS.  21  and  22   .  FIG.  21    conceptually illustrates an example determining a slope of a road on which to place of a road label.  FIG.  22    conceptually illustrates an example of a road label placed on a slope of a road according to some embodiments of the invention. 
     As shown, the process  2000  begins by identifying (at  2005 ) a road label in the layout of map labels. The process  2000  of some embodiments identifies a road label in the layout by scanning the layout from left-to-right while the process  2000  of other embodiments identifies a road label in the layout by scanning the layout from top-to-bottom. Still, in some embodiments, the process  2000  uses a combination of scanning the layout left-to-right and top-to-bottom to identify a road label in the layout. 
     Next, the process  2000  identifies (at  2010 ) two points in a portion of a Mercator map. In some embodiments, the two points are (1) a point along a road at which the first character of the road label is placed and (2) another point along the road at which the last character of the road label is placed. Referring to  FIG.  21    as an example, the left side of  FIG.  21    shows a two points pA and pB on a portion of a Mercator map  2100 . In this example, the points correspond to a first point along a road  2105  at which the first character of a road label (not shown in this figure) is placed and a second point along the road at which the last character of the road label is placed. 
     The process  2000  then determines (at  2015 ) corresponding points in a geocentric map. In some embodiments, the geocentric map is a map of the Earth that is described with respect to the center of the Earth. For instance, in some embodiments, a particular point in the geocentric map corresponds to a point on the surface of the Earth and has coordinates that are described with respect to the center of the Earth. Continuing with the example in  FIG.  21   , the right side of  FIG.  21    illustrates two points pA′ and pB′ in a portion of a geocentric map  2110  that corresponds to the points pA and pB in the portion of the Mercator map  2100 . 
     After determining points in the geocentric map, the process  2000  generates (at  2020 ) a frame in the geocentric map based on the determined points in the geocentric map, In some embodiments, the generated frame is a plane that includes the determined points in the geocentric map. That is, the generated frame is a plane in which the determined points are coplanar. Continuing with the example in  FIG.  21   , the right side of  FIG.  21    illustrates a frame  2115  generated based on the two points pA′ and pB′ in a portion of the geocentric map  2110 , In addition, the right side of  FIG.  21    shows vectors vUp, vA, vB, and vC, The vector vUp is collinear with a vector that starts from the center of the Earth (not shown in this figure) and passes through the point pA′, The vector vA is a vector that starts from the point pA′ and passes through the point pB′. The vector vB is a cross product of the vectors vUp and vA. The vector vC is the cross product of the vectors vA and vB. To generate the frame  2115 , the process  2000  of some embodiments determines a plane that is perpendicular to the vector vC and generates a two-dimensional rectangular shape along the determined plane. 
     Returning to  FIG.  20   , the process  2000  then applies (at  2025 ) the portion of the Mercator map on the generated frame. In some embodiments, the process  2000  applies the portion of the Mercator map on the generated frame by mapping the road in the portion of the Mercator map associated with the map label to the generated frame in the geocentric map. Continuing with the example in  FIG.  21   , the right side of  FIG.  21    shows a road  2120  on the frame  2115 . For this example, the road  2120  is the road  2105  after it has been translated to the portion of the geocentric map  2110 . 
     Next, the process  2000  places (at  2030 ) the identified road label on the frame. The process  2000  of some embodiments places the road label on the frame in the same or similar manner that described above by reference to  FIG.  7   . In particular, in some embodiments, the process  2000  places the characters of the road label such that the road label follows the curvature of the road to which the road name is associated. In other words, each character of the road label is placed along the road so that a line that bisects the character is tangent to the road at the point at which the line intersects the road. As an example,  FIG.  22    conceptually illustrates a road label placed on a slope of a road. Specifically,  FIG.  22    shows a rendered view of a 3D map. As shown, the view of the 3D map includes a road  2205  the slopes up and towards the right and a road label “Incline Rd” that is placed along the slop of the road. In some embodiments, the mapping application renders the view of the 3D map, renders the road label using the technique described above, and superimposes the road label over the map view of the 3D map. 
     Finally, the process  2000  determines (at  2035 ) whether any map label in the layout is left to process. In some embodiments, the process  2000  uses the techniques described above to scan the layout for any map label left to process. When the process  2000  determines that a map label in the layout is left to process, the process  2000  returns to  2005   s  to continue processing any remaining map labels in the layout. Otherwise, the process  2000  ends. 
     III. Rendering Map labels 
     In some embodiments, once the mapping application processes roads and determines a layout of map labels, the mapping application renders a view of the map and map labels for map elements and/or constructs in the map view.  FIG.  23    conceptually illustrates a process  2300  of some embodiments for rendering map labels for a map view. The mapping application of some embodiments described above and below by reference to  FIGS.  1 ,  2 ,  19 ,  22 , and  25    performs the process  2300 . In some embodiments, the mapping application performs the process  2300  as part of operation  315  described above by reference to  FIG.  3   . 
     As shown, the process  2300  starts by generating (at  2305 ) label meshes for map labels. In sonic embodiments, the process  2300  generate a mesh (e.g., by creating a data structure that stores data describing the mesh) for each map label that is to be rendered. 
     Next, the process  2300  loads (at  2310 ) the glyphs for the map labels. As described above by reference to  FIG.  7   , some embodiments determines the shape for each character in a string of a map label based on a specified letterform that is derived from a texture atlas for the specified letterform. The texture atlas of some embodiments is pre-rendered and includes a collection of sub-images that correspond to different letters of the letterform. For each glyph character) in a particular map label, the process  2300  loads the corresponding sub-image. 
     The process  2300  then applies (at  2315 ) animation for the map view. In some embodiments, the process  2300  provides animations for any number of different to animate transitions between displaying different map labels. For instance, the process  2300  of some embodiments provides animations that include fading map labels in and/or out when zoom or pan operations are performed on the map, cross fading upside down map labels with right side up versions of the map labels when rotate operations are performed, fading map labels in and/or out when colliding map labels are detected, cross fading different styles of map labels when the styling of map labels change (e.g., in response to zooming into and out from the map), etc. 
     Finally, the process  2300  draws (at  2320 ) the view of the map for display on a device on which the mapping application of some embodiments is operating and then the process  2300  ends. In some embodiments, the process  2300  draws the view of the map based on a virtual camera that is used to identify a position and orientation from which to render the view of the map. Different embodiments of the process  2300  render different types of map labels using different techniques. For instance, the process  2300  of some embodiments renders map views by superimposing 2D map labels (e.g., road labels, POI labels, POI labels, etc.) over rendered map views of the map. That is, in some such embodiments, the process  2300  renders a map view of the map and then adds 2D map labels to the rendered map view by overlaying the 2D map labels onto the map view. 
     For 3D maps, the process  2300  in some embodiments adds polygons that represent map labels (e.g., road path indicators) to the 3D map and renders map views of the 3D map with the added polygons. In other words, in some such embodiments, the process  2300  adds map labels to the 3D map before the process  2300  renders map views of the 3D map. In some embodiments, the map labels are part of the 3D map (as opposed to adding the map labels to the 3D map) and the process  2300  renders the map labels that are to be displayed in the map view. For map labels that are not to be rendered in the map view, the process  2300  of some such embodiments ignores such map labels that the process  2300  rendering in the map view of the 3D map. 
       FIG.  24    conceptually illustrates a process  2400  of some embodiments for rendering map labels based on different adjustments to a view of a map. In some embodiments, the mapping application described above and below by reference to  FIGS.  1 ,  2 ,  19 ,  22 , and  25    performs the process  2400  when the mapping application is in a hybrid-viewing mode or a standard-viewing mode and a user provides input to modify the view of the map. 
     The process  2400  begins by receiving (at  2405 ) input to modify the view of the map. In some embodiments, any number of different inputs modifies the view of the map. Examples of inputs include touch input, multi-touch input, gesture input, cursor input, keyboard or keypad input, etc. 
     Next, the process  2400  determines (at  2410 ) whether the received input is for rotating the view of the map. In some embodiments, a multi-touch gesture input, such as the input described above by reference to  FIG.  1   , is defined for rotating the view of the map. Additional and/or different inputs are defined for rotating the view of the map in some embodiments. 
     When the process  2400  determines that the received input is not for rotating the view of the map, the process  2400  proceeds to  2425 . When the process  2400  determines that the received input is for rotating the view of the map, the process  2400  determines (at  2415 ) whether map labels rotated past a threshold angle (e.g., 10 degrees, 15 degrees, 25 degrees, etc.). In some embodiments, the angle that the process  2400  uses for this determination is formed by (1) a vector along a particular road label that starts from the center of the particular road label and projects towards the end of the particular road label and (2) a vector that starts from the center of the particular road label and projects upwards along a vertical axis of the GUI of the mapping application. 
     If the process  2400  determines that no map labels rotated past a. threshold angle, the process  2400  proceeds to  2440 . Otherwise, the process  2400  provides (at  2420 ) a transition to display inverted versions of the map labels and then proceeds to  2440 . In some embodiments, the process  2400  provides a transition to display the inverted version of a particular road label by cross fading the particular road label and the inverted version (i.e., right side up version) of the particular road label. In particular, the process  2400  of some such embodiments displays an animation that fades out the particular road label while fading in the inverted version (i.e., the right side up version) of the particular road label. In some embodiments, the process  2400  uses additional and/or different techniques to transition from displaying an upside down road label to displaying a right side up version of the road label. 
     At  2425 , the process  2400  determines whether the received input is for adjusting the zoom (i.e., distance) of the view of the map. In some embodiments, a multi-touch gesture input, such as the input described above by reference to  FIG.  2   , is defined for adjusting the zoom of the view of the map. Additional and/or different inputs are defined for adjusting the zoom of the view of the map in some embodiments. 
     When the process  2400  determines that the received input is not for adjusting the view of the view of the map, the process  2400  proceeds to  2440 , Otherwise, the process  2400  determines (at  2430 ) whether styles have changed for any map labels. In some embodiments, the styling of the map labels includes the type of font, the color, and the size of the characters to use for the different map labels. As explained above, some embodiments determine the styling of map labels based on localization factors, such as language settings, time zone settings, etc., and/or a style sheet that specifies styling of the map labels. In some embodiments, the style sheet specifies styling according to the type of map element and/or map construct (e.g., a freeway, a suburban street, a city, a state, a continent, etc.) for which map labels are rendered, the type of device (e.g., a smartphone, a table computing device, a desktop computer, a laptop computer, etc.) for which the mapping application is operating, etc. 
     If the process  2400  determines that styles have not changed for any map labels, the process  2400  proceeds to  2440 . Otherwise, process  2400  provides (at  2435 ) a transition to display map labels with new styles. In some embodiments, the process  2400  provides a transition to display the map labels with new styles by cross fading the map labels and a version of the map labels with the new styles. That is, the process  2400  of some embodiments displays an animation that fades out the map labels that have changes styles while fading in the version of the map labels with the new styles. The process  2400  of some embodiments uses additional and/or different techniques to transition from displaying map labels with a first style to displaying the map labels with a second style. 
     Finally, the process  2400  determines (at  2420 ) whether any input to modify the view of the map is received. When the process  2400  determines that input to modify the view of the map is received, the process  2400  returns to  2410  to process the input. Otherwise, the process  2400  ends. 
       FIG.  25    conceptually illustrates a mapping application of some embodiments rendering different styles of map labels and/or different map labels based on different zoom levels from which a map is viewed. In particular,  FIG.  25    illustrates the GUI  100  of the mapping application of some embodiments operating on a device (e.g., a mobile device, a table computing device, etc.) at four different stages  2505 - 2520  of zooming into a view of the map. 
     The first stage  2505  shows the GUI  100  displaying a view of the map. In some embodiments, map view is a view of a 2D map while, in other embodiments, or the map view is a top-down view of a 3D map. In the first stage  2505 , the map view includes several roads, a city indicator, and a city label indicating the name of the city (“Old Town City” in this example). As shown, some of the roads are displayed as thicker lines to indicate a type of road (e.g., highway roads, expressway roads, arterial roads, etc.) while some of the other roads are displayed as thinner lines to indicate another type of road (e.g., collector roads, back roads, etc.). 
     In addition, the first stage  2505  shows a user performing a zoom operation in order to zoom into the view of the map (i.e., to view the map at a closer distance). In this example, the user is providing a multi-touch gesture by placing two fingers on a touchscreen of the device and moving the two fingers in directions away from each other in order to zoom into the map view. 
     The second stage  2510  illustrates the GUI  100  after the user has completed the zoom operation on the map view in the first stage  2505 . As illustrated, the roads in this stage are thicker and the city indicator is no longer displayed as a result of the zooming operation. In some embodiments, the mapping application maintains the same size font of map labels when the view of the map is zoomed in. As shown, the city label “Old Town City” remains the same size relative to the GUI  100  even though the view of the map in the second stage  2510  is closer compared to the view of the map in the first stage  2505 . 
     The second stage  2510  also illustrates the user performing another zoom operation in order to zoom further into the view of the map. The user in this example is providing a multi-touch gesture by placing two fingers on a touchscreen of the device and moving the two fingers in directions away from each other in order to zoom into the map view. 
     The third stage  2515  illustrates the GUI  100  after the user has completed the zoom operation on the map view in the second stage  2510 . As illustrated, the roads in this stage are thicker and several road labels (“Elm Ave”, “Woodland St”, and “Oak Ave” in this example) are displayed as a result of the zooming operation. As mentioned above, the mapping application of some embodiments maintains the same size font of map labels when the view of the map is zoomed in. As illustrated in the third stage  2515 , the city label “Old Town City” remains the same size relative to the GUI  100  even though the view of the map in the third stage  2515  is closer compared to the view of the map in the second stage  2510 . 
     Additionally, the third stage  2515  shows the user performing yet another zoom operation in order to zoom even further into the view of the map. In this example, the user is providing a multi-touch gesture by placing two fingers on a touchscreen of the device and moving the two fingers in directions away from each other in order to zoom into the map view. 
     The fourth stage  2520  illustrates the GUI  100  after the user has completed the zoom operation on the map view in the third stage  2515 . As shows, the roads in this stage are thicker. In some embodiments, the mapping application changes the styling of map labels when the zoom level passes a threshold level. In this example, the mapping application displays a different style for the city label “Old Town City” by displaying a version of the city label with larger characters (i.e., font size). 
     The previously described  FIGS.  1  and  24    illustrate one approach that the mapping application of some embodiments uses to display road labels when a rotate operating is performed on a map. In some embodiments, the mapping application uses other novel techniques to display other map labels in a map view when rotate operations are performed on the map.  FIG.  26    illustrates one example of this novel approach in terms of four stages  2605 - 2620  that show rendering map labels when rotating a map. 
     The first stage  2605  illustrates a map view that includes a POI indicator  2625  that indicates the location of the POI in the map view and a POI label  2630  that indicates the name of the POI, which is Apple Inc. In this example. As shown in the first stage  2605 , the POI indicator  2625  and the POI label  2630  are displayed upright. In the second and third stages  2610  and  2615 , the mapping application is rotating the map in response to a rotation operation provided by a user&#39;s two-finger multi-touch gesture on a touchscreen of the device on which the mapping application is operating. In both of these stages  2610  and  2615 , the POI indicator  2625  and the POI label  2630  are shown to slightly rotate at a much smaller angle than the rotation angle of the map. The behavior of the POI indicator  2625  and the POI label  2630  is as if the POI indicator  2625  and the POI  2630  are pinned at the POI indicator  2625 &#39;s center or top to the map but their center of gravity points downwards. Hence, whenever the map rotates, the POI indicator  2625  and the POI label  2630  slightly rotate as well, but their center of gravity makes them rotate less and eventually brings the POI indicator  2625  and the POI label  2630  back to their upright positions, These upright positions of the POI indicator  2625  and the POI label  2630  are shown in the fourth stage  2620 . This stage shows the map view after the rotation operation has completed. 
     While  FIG.  26    shows an example of the mapping application displaying a POI indicator and POI label when a map is being rotated, the mapping application of some embodiments uses the same or similar approach to display other types of map labels when the map is being rotated. For instance, in some embodiments, the mapping application uses such an approach to display city labels, state labels, continent labels, body of water labels, etc., when the map is being rotated. 
     Maintaining the constant upright position of map labels while a map is rotated, however, might be a little bit distracting when the map has many map labels and many of them arc fighting against the rotation to remain straight up. Accordingly, for some of map labels, the mapping application of some embodiments employs an alternative mechanism to adjust their orientation during a rotation. 
       FIG.  27    conceptually illustrates the mapping application of some embodiments rendering POI banner map labels when rotating a map. In particular,  FIG.  27    illustrates the GUI  100  of the mapping application of some embodiments at four different stages  2705 - 2720  of rotating a view of a map. 
     The first stage  2705  is similar to the first stage  205  described above by reference to  FIG.  2    except the map view in the first stage  2705  only displays the road label for Elm Ave. In addition, the first stage  2705  of the GUI  100  illustrates a user selecting the POI indicator  225  by using a finger to tap on the touchscreen of the device in order to provide options regarding the POI. 
     The second stage  2710  illustrates the GUI  100  displaying a banner  2725  in response to the selection of the POI indicator  225 . As illustrated, the banner  2725  includes the name of the POI, a selectable UI item  2730  for invoking a route navigation to the POI, and a selectable UI item  2735  for displaying information about the POI. 
     Next, the third stage  2715  illustrates the user performing, a rotate operation in order to rotate the map view. In this example, the user is providing a multi-touch gesture by placing two fingers on the touchscreen and rotating the two fingers in a clockwise direction about a location on the touchscreen (e.g., a midpoint between an initial pair of points where the two fingers touch the touchscreen) in order to rotate the map view in a clockwise direction. 
     When the mapping application receives the described multi-touch gesture to rotate the map view, the mapping application of some embodiments rotates the map view and the road labels in the map view, but continues to display the POI indicator  225 , POI label  230 , and the banner  2725  in an upright manner. As shown in the third stage  2715 , the mapping application has rotated the road label “Elm Ave” in a clockwise direction about the center of the road label the same degree that the map view has been rotated. Additionally, the mapping application maintains displaying the POI indicator  225 , POI label  230 , and the banner  2725  upright. 
     The fourth stage  2720  illustrates the map view after the user has finished rotating the map view. As illustrated the mapping application in the fourth stage  2720  has rotated the map view further in the clockwise direction than that shown in the third stage  2715 . The mapping application has also rotated the road label “Elm Ave” further in the clockwise direction about the center of the road label the same degree as the rotation of the map view. For the POI indicator  225 , POI label  230 , and the banner  2725 , the mapping application displayed them upright throughout the rotation of the map view. 
     Although  FIG.  27    shows an example of the mapping application displaying a POI indicator, POI label, and a user-invoked banner for the POI when a map is being rotated, in some embodiments, the mapping application uses the same or similar technique to display other types of map labels and/or user-invoked map labels when the map is being rotated. For instance, the mapping application of some embodiments uses such a technique for displaying user-invoked banners for user-specified graphical location indicators (e.g., pins). 
     Many of the details, examples, and embodiments described above (e.g.,  FIGS.  1 ,  2 , and  25 - 27   ) are shown with the mapping application rendering map views from a 2D perspective of a 3D map (i.e., a top-down view of the 3D map) for purposes of explanation and simplicity. However, one of ordinary skill in the art will realize that the invention is not limited to those details, examples, and embodiments. That is, the mapping application of some embodiments uses the same or similar techniques described in those details, examples, and embodiments when rendering map views from a 3D perspective of the 3D map. 
     IV. Electronic System 
     Many of the above-described features and applications are implemented as software processes that are specified as a set of instructions recorded on a computer readable storage medium (also referred to as computer readable medium). When these instructions are executed by one or more computational or processing unit(s) (e.g., one or more processors, cores of processors, or other processing units), they cause the processing unit(s) to perform the actions indicated in the instructions. Examples of computer readable media include, but are not limited to, CD-ROMs, flash drives, random access memory (RAM) chips, hard drives, erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), etc. The computer readable media does not include carrier waves and electronic signals passing wirelessly or over wired connections. 
     In this specification, the term “software” is meant to include firmware residing in read-only memory or applications stored in magnetic storage which can be read into memory for processing by a processor. Also, in some embodiments, multiple software inventions can be implemented as sub-parts of a larger program while remaining distinct software inventions. In some embodiments, multiple software inventions can also be implemented as separate programs. Finally, any combination of separate programs that together implement a software invention described here is within the scope of the invention. In some embodiments, the software programs, when installed to operate on one or more electronic systems, define one or more specific machine implementations that execute and perform the operations of the software programs. 
     A. Mobile Device 
     The mapping application of some embodiments operate on mobile devices, such as smart phones (e.g., iPhones●) and tablets (e.g., iPads●).  FIG.  28    is an example of an architecture  2800  of such a mobile computing device. Examples of mobile computing devices include smartphones, tablets, laptops, etc. As shown, the mobile computing device  2800  includes one or more processing units  2805 , a memory interface  2810  and a peripherals interface  2815 . 
     The peripherals interface  2815  is coupled to various sensors and subsystems, including a camera subsystem  2820 , a wireless communication subsystem(s)  2825 , an audio subsystem  2830 , an I/O subsystem  2835 , etc. The peripherals interface  2815  enables communication between the processing units  2805  and various peripherals. For example, an orientation sensor  2845  (e.g., a gyroscope) and an acceleration sensor  2850  (e.g., an accelerometer) is coupled to the peripherals interface  2815  to facilitate orientation and acceleration functions, 
     The camera subsystem  2820  is coupled to one or more optical sensors  2840  (e.g., a charged coupled device (CCD) optical sensor, a complementary metal-oxide-semiconductor (CMOS) optical sensor, etc.). The camera subsystem  2820  coupled with the optical sensors  2840  facilitates camera functions, such as image and/or video data capturing. The wireless communication subsystem  2825  serves to facilitate communication functions. In some embodiments, the wireless communication subsystem  2825  includes radio frequency receivers and transmitters, and optical receivers and transmitters (not shown in  FIG.  28   ). These receivers and transmitters of some embodiments are implemented to operate over one or more communication networks such as a GSM network, a Wi-Fi network, a Bluetooth network, etc. The audio subsystem  2830  is coupled to a speaker to output audio (e.g., to output voice navigation instructions). Additionally, the audio subsystem  2830  is coupled to a microphone to facilitate voice-enabled functions, such as voice recognition (e.g., for searching), digital recording, etc. 
     The I/O subsystem  2835  involves the transfer between input/output peripheral devices, such as a display, a touchscreen, etc., and the data bus of the processing units  2805  through the peripherals interface  2815 . The I/O subsystem  2835  includes a touchscreen controller  2855  and other input controllers  2860  to facilitate the transfer between input/output peripheral devices and the data bus of the processing units  2805 . As shown, the touchscreen controller  2855  is coupled to a touchscreen  2865 . The touchscreen controller  2855  detects contact and movement on the touchscreen  2865  using any of multiple touch sensitivity technologies, The other input controllers  2860  are coupled to other input/control devices, such as one or more buttons. Some embodiments include a near-touch sensitive screen and a corresponding controller that can detect near-touch interactions instead of or in addition to touch interactions. 
     The memory interface  2810  is coupled to memory  2870 . In some embodiments, the memory  2870  includes volatile memory (e.g., high-speed random access memory), non-volatile memory (e.g., flash memory), a combination of volatile and non-volatile memory, and/or any other type of memory. As illustrated in  FIG.  28   , the memory  2870  stores an operating system (OS)  2872 . The OS  2872  includes instructions for handling basic system services and for performing hardware dependent tasks. 
     The memory  2870  also includes communication instructions  2874  to facilitate communicating with one or more additional devices; graphical user interface instructions  2876  to facilitate graphic user interface processing; image processing instructions  2878  to facilitate image-related processing and functions; input processing instructions  2880  to facilitate input-related (e.g., touch input) processes and functions; audio processing instructions  2882  to facilitate audio-related processes and functions; and camera instructions  2884  to facilitate camera-related processes and functions. The instructions described above are merely exemplary and the memory  2870  includes additional and/or other instructions in sonic embodiments. For instance, the memory for a smartphone may include phone instructions to facilitate phone-related processes and functions. Additionally, the memory may include instructions for a mapping application as well as other applications. The above-identified instructions need not be implemented as separate software programs or modules. Various functions of the mobile computing device can be implemented in hardware and/or in software, including in one or more signal processing and/or application specific integrated circuits. 
     While the components illustrated in  FIG.  28    are shown as separate components, one of ordinary skill in the art will recognize that two or more components may be integrated into one or more integrated circuits. In addition, two or more components may be coupled together by one or more communication buses or signal lines. Also, while many of the functions have been described as being performed by one component, one of ordinary skill in the art will realize that the functions described with respect to  FIG.  28    may be split into two or more integrated circuits. 
     B. Computer System 
       FIG.  29    conceptually illustrates another example of an electronic system  2900  with which some embodiments of the invention are implemented. The electronic system  2900  may be a computer a desktop computer, personal computer, tablet computer, etc.), phone, PDA, or any other sort of electronic or computing device. Such an electronic system includes various types of computer readable media and interfaces for various other types of computer readable media. Electronic system  2900  includes a bus  2905 , processing unit(s)  2910 , a graphics processing unit (GPO  2915 , a system memory  2920 , a network  2925 , a read-only memory  2930 , a permanent storage device  2935 , input devices  2940 , and output devices  2945 . 
     The bus  2905  collectively represents all system, peripheral, and chipset buses that communicatively connect the numerous internal devices of the electronic system  2900 . For instance, the bus  2905  communicatively connects the processing unit(s)  2910  with the read-only memory  2930 , the GPU  2915 , the system memory  2920 , and the permanent storage device  2935 . 
     From these various memory units, the processing unit(s)  2910  retrieves instructions to execute and data to process in order to execute the processes of the invention. The processing unit(s) may be a single processor or a multi-core processor in different embodiments. Some instructions are passed to and executed by the GPU  2915 . The CPU  2915  can offload various computations or complement the image processing provided by the processing unit(s)  2910 . in some embodiments, such functionality can be provided using CoreImage&#39;s kernel shading language. 
     The read-only-memory (ROM)  2930  stores static data and instructions that are needed by the processing unit(s)  2910  and other modules of the electronic system. The permanent storage device  2935 , on the other hand, is a read-and-write memory device. This device is a non-volatile memory unit that stores instructions and data even when the electronic system  2900  is off. Some embodiments of the invention use a mass-storage device (such as a magnetic or optical disk and its corresponding disk drive, integrated flash memory) as the permanent storage device  2935 . 
     Other embodiments use a removable storage device (such as a floppy disk, flash memory device, etc., and its corresponding drive) as the permanent storage device. Like the permanent storage device  2935 , the system memory  2920  is a read-and-write memory device. However, unlike storage device  2935 , the system memory  2920  is a volatile read-and-write memory, such a random access memory. The system memory  2920  stores some of the instructions and data that the processor needs at runtime, in some embodiments, the invention&#39;s processes are stored in the system memory  2920 , the permanent storage device  2935 , and/or the read-only memory  2930 . From these various memory units, the processing unit(s)  2910  retrieves instructions to execute and data to process in order to execute the processes of some embodiments. 
     The bus  2905  also connects to the input and output devices  2940  and  2945 . The input devices  2940  enable the user to communicate information and select commands to the electronic system. The input devices  2940  include alphanumeric keyboards and pointing devices (also called “cursor control devices”), cameras (e.g., webcams), microphones or similar devices for receiving voice commands, etc. The output devices  2945  display images generated by the electronic system or otherwise output data. The output devices  2945  include printers and display devices, such as cathode ray tubes (CRT) or liquid crystal displays (LCD), as well as speakers or similar audio output devices. Some embodiments include devices such as a touchscreen that function as both input and output devices. 
     Finally, as shown in  FIG.  29   , bus  2905  also couples electronic system  2900  to a network  2925  through a network adapter (not shown). In this manner, the computer can be a part of a network of computers (such as a local area network (“LAN”), a wide area network (“WAN”), or an Intranet, or a network of networks, such as the Internet. Any or all components of electronic system  2900  may be used in conjunction with the invention. 
     Some embodiments include electronic components, such as microprocessors, storage and memory that store computer program instructions in a machine-readable or computer-readable medium (alternatively referred to as computer-readable storage media, machine-readable media, or machine-readable storage media). Some examples of such computer-readable media include RAM, ROM, read-only compact discs (CD-ROM), recordable compact discs (CD-ROM, rewritable compact discs (CD-RW), read-only digital versatile discs (e.g., DVD-ROM, dual-layer DVD-ROM), a variety of recordable/rewritable DVDs (e.g., DVD-RAM, DVD-RW, DVD+RW, etc.), flash memory (e.g., SD cards, mini-SD cards, micro-SD cards, etc.), magnetic and/or solid state hard drives, read-only and recordable Blu-Ray discs, ultra density optical discs, any other optical or magnetic media, and floppy disks. The computer-readable media may store a computer program that is executable by at least one processing unit and includes sets of instructions for performing various operations. Examples of computer programs or computer code include machine code, such as is produced by a compiler, and files including higher-level code that are executed by a computer, an electronic component, or a microprocessor using an interpreter. 
     While the above discussion primarily refers to microprocessor or multi-core processors that execute software, some embodiments are performed by one or more integrated circuits, such as application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs). In some embodiments, such integrated circuits execute instructions that are stored on the circuit itself In addition, some embodiments execute software stored in programmable logic devices (PLDs), ROM, or RAM devices. 
     As used in this specification and any claims of this application, the terms “computer”, “server”, “processor”, and “memory” all refer to electronic or other technological devices. These terms exclude people or groups of people. For the purposes of the specification, the terms display or displaying means displaying on an electronic device. As used in this specification and any claims of this application, the terms “computer readable medium,” “computer readable media,” and “machine readable medium” are entirely restricted to tangible, physical objects that store information in a form that is readable by a computer. These terms exclude any wireless signals, wired download signals, and any other ephemeral signals. 
     V. Map Service Environment 
     Various embodiments may operate within a map service operating environment.  FIG.  30    illustrates a map service operating environment, according to some embodiments. A map service  3030  (also referred to as mapping service) may provide map services for one or more client devices  3002   a - 3002   c  in communication with the map service  3030  through various communication methods and protocols. A map service  3030  in some embodiments provides map information and other map-related data, such as two-dimensional map image data (e.g., aerial view of roads utilizing CCIs), three-dimensional map image data (e.g., traversable map with three-dimensional features, such as buildings), route and direction calculations (e.g., ferry route calculations or directions between two points for a pedestrian), real-time navigation data (e.g., turn-by-turn visual navigation data in two or three dimensions), location data (e.g., where the client device currently is located), and other geographic data (e.g., wireless network coverage, weather, traffic information, or nearby points-of-interest). In various embodiments, the map service data may include localized labels for different countries or regions. Localized labels may be utilized to present map labels (e.g., street names, city names, points of interest) in different languages on client devices. Client devices  3002   a - 3002   c  may utilize these map services by obtaining map service data. Client devices  3002   a - 3002   c  may implement various techniques to process map service data. Client devices  3002   a - 3002   c  may then provide map services to various entities, including, but not limited to, users, internal software or hardware modules, and/or other systems or devices external to the client devices  3002   a - 3002   c.    
     In some embodiments, a map service is implemented by one or more nodes in a distributed computing system. Each node may be assigned one or more services or components of a map service. Some nodes may be assigned the same map service or component of a map service. A load balancing node in some embodiments distributes access or requests to other nodes within a map service. In some embodiments a map service is implemented as a single system, such as a single server. Different modules or hardware devices within a server may implement one or more of the various services provided by a map service. 
     A map service in sonic embodiments provides map services by generating map service data in various formats. In some embodiments, one format of map service data is map image data. Map image data provides image data to a client device so that the client device may process the image data (e.g., rendering and/or displaying the image data as a two-dimensional or three-dimensional map). Map image data, whether in two or three dimensions, may specify one or more map tiles. A map tile may be a portion of a larger map image. Assembling together the map tiles of a map produces the original map. Tiles may be generated from map image data, routing or navigation data, or any other map service data. In some embodiments map tiles are raster-based map tiles, with tile sizes ranging from any size both larger and smaller than a commonly-used 256 pixel by 256 pixel tile. Raster-based map tiles may be encoded in any number of standard digital image representations including, but not limited to, Bitmap (.bmp), Graphics Interchange Format (.gif), Joint Photographic Experts Group (.jpg, .jpeg, etc.), Portable Networks Graphic (.png), or Tagged Image File Format (.tiff). In some embodiments, map tiles are vector-based map tiles, encoded using vector graphics, including, but not limited to, Scalable Vector Graphics (.svg) or a Drawing File (.drw). Some embodiments also include tiles with a combination of vector and raster data. Metadata or other information pertaining to the map tile may also be included within or along with a map tile, providing further map service data to a client device. In various embodiments, a map tile is encoded for transport utilizing various standards and/or protocols, some of which are described in examples below. 
     In various embodiments, map tiles may be constructed from image data of different resolutions depending on zoom level. For instance, for low zoom level (e.g., world or globe view), the resolution of map or image data need not be as high relative to the resolution at a high zoom level (e.g., city or street level). For example, when in a globe view, there may be no need to render street level artifacts as such objects would be so small as to be negligible in many cases. 
     A map service in some embodiments performs various techniques to analyze a map tile before encoding the tile for transport. This analysis may optimize map service performance for both client devices and a map service. In some embodiments map tiles are analyzed for complexity, according to vector-based graphic techniques, and constructed utilizing complex and non-complex layers. Map tiles may also be analyzed for common image data or patterns that may be rendered as image textures and constructed by relying on image masks. In some embodiments, raster-based image data in a map tile contains certain mask values, which are associated with one or more textures. Some embodiments also analyze map tiles for specified features that may be associated with certain map styles that contain style identifiers. 
     Other map services generate map service data relying upon various data formats separate from a map tile in some embodiments. For instance, map services that provide location data may utilize data formats conforming to location service protocols, such as, but not limited to, Radio Resource Location services Protocol (RRLP), TIA 801 for Code Division Multiple Access (CDMA), Radio Resource Control (RRC) position protocol, or LTE Positioning Protocol (LPP). Embodiments may also receive or request data from client devices identifying device capabilities or attributes (e.g., hardware specifications or operating system version) or communication capabilities (e.g., device communication bandwidth as determined by wireless signal strength or wired or wireless network type). 
     A map service may obtain map service data from internal or external sources. For example, CCIs used in map image data may be obtained from external services, or internal systems, storage devices, or nodes. Other examples may include, but are not limited to, GPS assistance servers, wireless network coverage databases, business or personal directories, weather data, government information construction updates or road name changes), or traffic reports. Some embodiments of a map service may update map service data (e.g., wireless network coverage) for analyzing future requests from client devices. 
     Various embodiments of a map service respond to client device requests for map services. These requests may be a request for a specific map or portion of a map. Some embodiments format requests for a map as requests for certain map tiles. In some embodiments, requests also supply the map service with starting locations (or current locations) and destination locations for a route calculation. A client device may also request map service rendering information, such as map textures or style sheets. In at least some embodiments, requests are so one of a series of requests implementing turn-by-turn navigation. Requests for other geographic data may include, but are not limited to, current location, wireless network coverage, weather, traffic information, or nearby points-of-interest. 
     A map service, in some embodiments, analyzes client device requests to optimize a device or map service operation. For instance, a map service may recognize that the location of a client device is in an area of poor communications (e.g., weak wireless signal) and send more map service data to supply a client device in the event of loss in communication or send instructions to utilize different client hardware (e.g., orientation sensors) or software (e.g., utilize wireless location services or Wi-Fi positioning instead of GPS-based services). In another example, a map service may analyze a client device request for vector-based map image data and determine that raster-based map data better optimizes the map image data according to the image&#39;s complexity. Embodiments of other map services may perform similar analysis on client device requests and as such the above examples are not intended to be limiting. 
     Various embodiments of client devices (e.g., client devices  3002   a - 3002   c ) are implemented on different portable-multifunction device types. Client devices  3002   a - 3002   c  utilize map service  3030  through various communication methods and protocols. In some embodiments, client devices  3002   a - 3002   c  obtain map service data from map service  3030 . Client devices  3002   a - 3002   c  request or receive map service data. Client devices  3002   a - 3002   c  then process map service data (e.g., render and/or display the data) and may send the data to another software or hardware module on the device or to an external device or system. 
     A client device, according to some embodiments, implements techniques to render and/or display maps. These maps may be requested or received in various formats, such as map tiles described above. A client device may render a map in two-dimensional or three-dimensional views. Some embodiments of a client device display a rendered map and allow a user, system, or device providing input to manipulate a virtual camera in the map, changing the map display according to the virtual camera&#39;s position, orientation, and field-of-view. Various forms and input devices are implemented to manipulate a virtual camera. In some embodiments, touch input, through certain single or combination gestures (e.g., touch-and-hold or a swipe) manipulate the virtual camera. Other embodiments allow manipulation of the device&#39;s physical location to manipulate a virtual camera. For instance, a client device may be tilted up from its current position to manipulate the virtual camera to rotate up. In another example, a client device may be tilted forward from its current position to move the virtual camera forward. Other input devices to the client device may be implemented including, but not limited to, auditory input (e.g., spoken words), a physical keyboard, mouse, and/or a joystick. 
     Some embodiments provide various visual feedback to virtual camera manipulations, such as displaying an animation of possible virtual camera manipulations when transitioning from two-dimensional map views to three-dimensional map views. Some embodiments also allow input to select a map feature or object (e.g., a building) and highlight the object, producing a blur effect that maintains the virtual camera&#39;s perception of three-dimensional space. 
     In some embodiments, a client device implements a navigation system (e.g., turn-by-turn navigation). A navigation system provides directions or route information, which may be displayed to a user. Some embodiments of a client device request directions or a route calculation from a map service. A client device may receive map image data and route data from a map service. In some embodiments, a client device implements a turn-by-turn navigation system, which provides real-time route and direction information based upon location information and route information received from a map service and/or other location system, such as a Global Positioning Satellite (GPS) system. A client device may display map image data that reflects the current location of the client device and update the map image data in real-time. A navigation system may provide auditory or visual directions to follow a certain route. 
     A virtual camera is implemented to manipulate navigation map data according to some embodiments. Some embodiments of client devices allow the device to adjust the virtual camera display orientation to bias toward the route destination. Some embodiments also allow the virtual camera to navigation tunas simulating the inertial motion of the virtual camera. 
     Client devices implement various techniques to utilize map service data from map service. Some embodiments implement some techniques to optimize rendering of two-dimensional and three-dimensional map image data. In some embodiments, a client device locally stores rendering information. For instance, a client stores a style sheet which provides rendering directions for image data containing style identifiers. In another example, common image textures may be stored to decrease the amount of map image data transferred from a map service. Client devices in different embodiments implement various modeling techniques to render two-dimensional and three-dimensional map image data, examples of which include, but are not limited to: generating three-dimensional buildings out of two-dimensional building footprint data; modeling two-dimensional and three-dimensional map objects to determine the client device communication environment; generating models to determine whether map labels are seen from a certain virtual camera position; and generating models to smooth transitions between map image data. In some embodiments, the client devices also order or prioritize map service data in certain techniques. For instance, a client device detects the motion or velocity of a virtual camera, which if exceeding certain threshold values, lower-detail image data is loaded and rendered for certain areas. Other examples include: rendering vector-based curves as a series of points, preloading map image data for areas of poor communication with a map service, adapting textures based on display zoom level, or rendering map image data according to complexity. 
     In some embodiments, client devices communicate utilizing various data formats separate from a map tile. For instance, some client devices implement Assisted Global Positioning Satellites (A-GPS) and communicate with location services that utilize data formats conforming to location service protocols, such as, but not limited to, Radio Resource Location services Protocol (RRLP), TIA 801 for Code Division Multiple Access (CDMA), Radio Resource Control (RRC) position protocol, or LTE Positioning Protocol (LPP). Client devices may also receive GPS signals directly. Embodiments may also send data, with or without solicitation from a map service, identifying the client device&#39;s capabilities or attributes (e.g., hardware specifications or operating system version) communication capabilities (e.g., device communication bandwidth as determined by wireless signal strength or wired or wireless network type). 
       FIG.  30    illustrates one possible embodiment of an operating environment  3000  for a map service  3030  and client devices  3002   a - 3002   c . In some embodiments, devices  3002   a ,  3002   b , and  3002   c  communicate over one or more wired or wireless networks  3010 . For example, wireless network  3010 , such as a cellular network, can communicate with a wide area network (WAN)  3020 , such as the Internet, by use of gateway  3014 . A gateway  3014  in some embodiments provides a packet oriented mobile data service, such as General Packet Radio Service (GPRS), or other mobile data service allowing wireless networks to transmit data to other networks, such as wide area network  3020 . Likewise, access device  3012  (e.g., IEEE 802.11g wireless access device) provides communication access to WAN  3020 . Devices  3002   a  and  3002   b  can be any portable electronic or computing device capable of communicating with a map service. Device  3002   c  can be any non-portable electronic or computing device capable of communicating with a map service. 
     In some embodiments, both voice and data communications are established over wireless network  3010  and access device  3012 . For instance, device  3002   a  can place and receive phone calls (e.g., using voice over Internet Protocol (VoIP) protocols), send and receive e-mail messages (e.g., using Simple Mail Transfer Protocol (SMTP) or Post Office Protocol 3 (POP3)), and retrieve electronic documents and/or streams, such as web pages, photographs, and videos, over wireless network  3010 , gateway  3014 , and WAN  3020  (e.g., using Transmission Control Protocol/Internet Protocol (TCP/IP) or User Datagram Protocol (UDP)). Likewise, in some implementations, devices  3002   b  and  3002   c  can place and receive phone calls, send and receive e-mail messages, and retrieve electronic documents over access device  3012  and WAN  3020 . In various embodiments, any of the illustrated client devices may communicate with map service  3030  and/or other service(s)  3050  using a persistent connection established in accordance with one or more security protocols, such as the Secure Sockets Layer (SSL) protocol or the Transport Layer Security (TLS) protocol. 
     Devices  3002   a  and  3002   b  can also establish communications by other means. For example, wireless device  3002   a  can communicate with other wireless devices (e.g., other devices  3002   b , cell phones, etc.) over the wireless network  3010 . Likewise devices  3002   a  and  3002   b  can establish peer-to-peer communications  3040  (e.g., a personal area network) by use of one or more communication subsystems, such as Bluetooth● communication from Bluetooth Special Interest Group, Inc. of Kirkland, Wash. Device  3002   c  can also establish peer to peer communications with devices  3002   a  or  3002   b  (not shown). Other communication protocols and topologies can also be implemented. Devices  3002   a  and  3002   b  may also receive Global Positioning Satellite (GPS) signals from GPS satellites  3060 . 
     Devices  3002   a ,  3002   b , and  3002   c  can communicate with map service  3030  over one or more wire and/or wireless networks,  3010  or  3012 . For instance, map service  3030  can provide map service data to rendering devices  3002   a ,  3002   b , and  3002   c . Map service  3030  may also communicate with other services  3050  to obtain data to implement map services. Map service  3030  and other services  3050  may also receive GPS signals from GPS satellites  3060 . 
     In various embodiments, map service  3030  and/or other service(s)  3050  are configured to process search requests from any of the client devices. Search requests may include but are not limited to queries for businesses, addresses, residential locations, points of interest, or some combination thereof Map service  3030  and/or other service(s)  3050  may be configured to return results related to a variety of parameters including but not limited to a location entered into an address bar or other text entry field (including abbreviations and/or other shorthand notation), a current map view (e.g., user may be viewing one location on the multifunction device while residing in another location), current location of the user (e.g., in cases where the current map view did not include search results), and the current route (if any). In various embodiments, these parameters may affect the composition of the search results (and/or the ordering of the search results) based on different priority weightings. In various embodiments, the search results that are returned may be a subset of results selected based on specific criteria including but not limited to a quantity of times the search result (e.g., a particular point of interest) has been requested, a measure of quality associated, with the search result (e.g., highest user or editorial review rating), and/or the volume of reviews for the search results (e.g., the number of times the search result has been review or rated). 
     In various embodiments, map service  3030  and/or other service(s)  3050  are configured to provide auto-complete search results that are displayed on the client device, such as within the mapping application. For instance, auto-complete search results may populate a portion of the screen as the user enters one or more search keywords on the multifunction device. In some cases, this feature may save the user time as the desired search result may be displayed before the user enters the full search query. In various embodiments, the auto complete search results may be search results found by the client on the client device (e.g., bookmarks or contacts), search results found elsewhere (e.g., from the Internet) by map service  3030  and/or other service(s)  3050 , and/or some combination thereof. As is the case with commands, any of the search queries may be entered by the user via voice or through typing. The multifunction device may be configured to display search results graphically within any of the map display described herein. For instance, a pin or other graphical indicator may specify locations of search results as points of interest. In various embodiments, responsive to a user selection of one of these points of interest (e.g., a touch selection, such as a tap), the multifunction device is configured to display additional information about the selected point of interest including but not limited to ratings, reviews or review snippets, hours of operation, store status (e.g., open for business, permanently closed, etc.), and/or images of a storefront for the point of interest. In various embodiments, any of this information may be displayed on a graphical information card that is displayed in response to the user&#39;s selection of the point of interest. 
     In various embodiments, map service  3030  and/or other service(s)  3050  provide one or more feedback mechanisms to receive feedback from client devices  3002   a - 3002   c . For instance, client devices may provide feedback on search results to map service  3030  and/or other service(s)  3050  (e.g., feedback specifying ratings, reviews, temporary or permanent business closures, errors etc.); this feedback may be used to update information about points of interest in order to provide more accurate or more up-to-date search results in the future. In some embodiments, map service  3030  and/or other service(s)  3050  may provide testing information to the client device (e.g., an A/B test) determine which search results are best. For instance, at random intervals, the client device may receive and present two search results to a user and allow the user to indicate the best result. The client device may report the test results to map service  3030  and/or other services)  3050  to improve future search results based on the chosen testing technique, such as an A/B test technique in which a baseline control sample is compared to a variety of single-variable test samples in order to improve results. 
     While the invention has been described with reference to numerous specific details, one of ordinary skill in the art will recognize that the invention can be embodied in other specific forms without departing from the spirit of the invention. In addition, a number of the figures (including  FIGS.  3 ,  4 ,  7 ,  9 ,  18 ,  20 ,  23 , and  24   ) conceptually illustrate a process. The specific operations of this process may not be performed in the exact order shown and described. The specific operations may not be performed in one continuous series of operations, and different specific operations may be performed in different embodiments. Furthermore, the process could be implemented using several sub-processes, or as part of a larger macro process. Thus, one of ordinary skill in the art would understand that the invention is not to be limited by the foregoing illustrative details, but rather is to be defined by the appended claims.