Patent Publication Number: US-11657578-B2

Title: Registration for augmented reality system for viewing an event

Description:
PRIORITY 
     This application claims priority to U.S. Provisional Patent Application No. 63/159,870, entitled “Augmented Reality System for Viewing an Event” and filed Mar. 11, 2021 by Jayaram et al., which is incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The present technology relates to the use of augmented reality (AR). 
     When viewing a sporting event or other activity/event, whether at the actual venue or remotely (such as on television), the activity may be difficult to follow or even see. Although broadcasters sometimes insert graphics into broadcast images or provide alternate views, these are selected by the broadcaster and may not correspond to what individual viewers would like to see. Additionally, when a viewer is watching an event at the venue, such added content may not be available to that viewer at the venue and, even when it is, would not correspond to different viewpoints of different individuals at the event. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1  and  2    illustrate examples of the presentation of AR graphics and added content at an outdoor venue and an indoor venue. 
         FIG.  3    is block diagram of elements for an embodiment of a system to register a user&#39;s mobile device and provide augmented reality content to the user&#39;s mobile device. 
         FIG.  4    is a high-level block diagram of one embodiment of a general computing system that can be used to implement various embodiments of the registration processor, registration server and/or content server. 
         FIG.  5    is a bock diagram of a mobile device that can be used for displaying graphics of a view at a venue. 
         FIG.  6    is a flowchart of one embodiment of a process for operation of an AR system to provide content to viewers at a venue. 
         FIG.  7 A  illustrates the collection of survey images by a survey camera at a venue. 
         FIG.  7 B  is a block diagram of an embodiment of a camera rig that can be used for taking the survey images. 
         FIG.  8    illustrates the collection of fiducials at a venue. 
         FIG.  9    is a flowchart of one embodiment of a process for preparing a venue for a survey. 
         FIG.  10    is a flowchart of one embodiment of a process for collecting survey images. 
         FIG.  11    is a high level flowchart of one embodiment of a process for processing imagery. 
         FIG.  12    illustrates embodiments for registration processing based on a three columned architecture. 
         FIGS.  13 A and  13 B  are flowcharts for embodiments of the registration and tracking process by the mobile device and of the registration process by the registration server. 
         FIG.  14 A  is a block diagram of an embodiment for the registration/content server. 
         FIGS.  14 B- 14 D  illustrate embodiments for the timing of the different parts of the registration process. 
         FIG.  15    illustrates the use of multiple mobile devices with the registration server and content server. 
         FIG.  16    is a block diagram of an embodiment for supplying content to one or more user&#39;s mobile devices. 
         FIG.  17    is a flowchart for one embodiment of a process for requesting and receiving graphics by a registered mobile device. 
         FIGS.  18  and  19    respectively illustrate examples of a tabletop embodiment for events at a golf course venue and a basketball venue, corresponding to the at-venue embodiments of  FIGS.  1  and  2   . 
         FIG.  20    is a bock diagram for a tabletop embodiment. 
         FIG.  21    is flowchart for the operation of tabletop embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following presents techniques for enhancing live sports action and other events for fans who attend events at the venue or to augment their watching experience remote from the venue using augmented reality (AR) with mobile telephones, headsets, glasses, smart televisions, or other devices. At an event&#39;s venue, live viewing can enhance the live viewing process, such as by providing individual viewers accurate real time playing surface registration, and allowing live dynamic event data visualization synchronized to the playing surface action so that the entire venue becomes the canvas with accurate wayfinding and location based proposals. At home or other remote viewing locations (such as a sports bar), live tabletop AR streaming can provide dynamic event data visualization synchronized to tabletop streaming and live dynamic event data visualization synchronized to live TV. The techniques can also provide gamification, whether though institutional gaming, friend-to-friend wagering, or similar play for fun. 
     To be able provide AR content to users that corresponds to their individual points of view, the users&#39; individual positions and orientations have to be precisely determined relative to the real world. For example, if the user is at a venue and is viewing the event on a smart phone, the position and orientation of the smart phone and its camera&#39;s images will have an internal set of coordinates that need to be correlated with the real world coordinates so that content based on real world coordinates can be accurately displayed on the camera&#39;s images. Similarly, when viewing an event on a television, the camera supplying an image will have its coordinate system correlated with the real world coordinate system. 
     One way to track a moving camera is through use of simple optical flow techniques to latch on to simple ephemeral patterns in an image and track them frame-to-frame; however, to relate this to the real world, there needs to be a separate process that identifies unique features in the image that have been surveyed and their real world locations used to accurately locate to the viewer. A traditional computer vision approach detects visual features in a reference image, creates a numeric descriptor for that feature, and save numeric descriptor in a database, along with real world location determined by some surveying technique. For a new image, features are then detected in the image, their descriptors computed and found in the database, and the corresponding spatial information in the database is used to determine a viewer&#39;s position and orientation. This approach has a number of limitations. In many sports venues, for example, fields of view are made up of organic, non-2-D shapes (for example, trees along a fairway of a golf course) that vary widely with viewing direction and are difficult to uniquely identify. Additionally, the images will often have large areas of features that should be ignored, like moving crowds, changing scoreboards, and moving shadows, for example. Other difficulties include changing lighting conditions that change the appearance of features and many detectable features that are not distinctive enough to be uniquely identified (such as tree trunks or repeating fence posts). 
     To improve upon this situation, the following discussion presents a number of novel techniques. By detecting specific kinds of features in an image (e.g., the ridge line and edges of a tent, trunks of tress, location of the peaks of the trees) that can be surveyed, the same details can be identified in an image, and, using starting estimates of view position and orientation (such as from smart phone&#39;s GPS, compass, and gravitometer), a correspondence can be established between what a user can see and what has been surveyed in a database. The system can optimize the match between a 2D image of expected features based on the database and position estimates versus the smart phone&#39;s 2D camera image. More specifically, rather than use every example of a visual feature, only certain examples of features are used, with iterative techniques applied to accurately identify those features by their 3D spatial location, even though each feature is not distinctive in itself. Employing multiple feature types together can provide a robust, flexible solution, so that rather than develop an ad-hoc solution for every different viewing environment, the system can create a framework to support detecting different specific features and using them all to solve location problems and add new kinds of features to support different environments. 
     Examples of different kinds of features that might be used include straight-line edges of man-made structures and the corners at which they meet, where these might have specific constraints such as one side of the edge is white and a certain number of pixels widths. For outdoor venues, an example can include tree trunks, where these might comprise the 3D points of the bottom and top of a clearly identifiable segment, plus its diameter. In a golf course example, an outline of a green against the rough, the outline of a sand bunker, or a cart path against grass can provide a curving line of points in 3D space. The outline of a tree, or tops of individual trees, against the sky can be a useful reference if it can provide a clean outline and the tree is far away. For any of the features, repeatability of detections regardless of light changes and moving shadows is an important characteristics. To survey the features, the 3D location of features can be measured using multiple views from different positions with instrumented cameras (e.g., cameras with sensors that measure location and/or orientation). 
     As used here, surveying a venue is the process of building a collection of features, represented by their logical description along with their 3D position information, in a spatially-organized database. For example, the locations of points could be measured directly, for example, by using a total station (theodolite) survey device, which can accurately measure azimuth, elevation, and distance to a point from a surveyed location and direction. These typically use laser range finding, but might also use multiple view paths, like a stadimeter. On a golf course, for example, sprinkler head locations are useful reference points with accurately surveyed locations. The surveying process may use cameras to collect video or still imagery from multiple locations for the venue. In some embodiments, these survey images can include crowd sourced images. These images are then registered to a real world coordinate system, typically by one or both of accurately measuring the location of the camera using GPS, or by use compass and inertial measurement unit (IMU). This may require special techniques like establishing a reference GPS base station to get sufficient accuracy. Fiducials (visual reference objects) can be placed in well-surveyed positions such that there can be several in the field of view of any image. The fiducials can also be used to infer the location of other distinctive points within the images. Based on the fiducials and the located distinctive points, the process can register other images that may not contain enough fiducials. In some embodiments, a path of images can be digitized, with features being registered from one image to the next without surveying fiducials and then use post-processing to optimize estimates of the position of those points to match surveyed reference points: For example, a fiducial in the first and last frame of a sequence of images may be enough to accurately position corresponding points across the sequence of images, or these may be determined by structure from motion techniques. 
     As used here, registration is the process of establishing a correspondence between the visual frames of reference. For example, registration may include establishing a correspondence between the visual frames of reference that the mobile viewing device establishes on the fly (the coordinates of the mobile device&#39;s frame of reference) and a coordinate system of a real world frame of reference. In many situations, an accurate orientation registration may be more important than position registration. Accuracy is determined by how much pixel error there is in, for example, placing a virtual graphic (e.g., image) at a specific location in a real world scene. In one set of embodiments, based on the internal coordinates for a frame of reference of a view-tracking app on a user&#39;s device (e.g., ARKit on an iPhone) for a particular image, this can provide information on how 3D rays to several points in the image from the user&#39;s mobile device can be used to establish a transformation between the user&#39;s mobile device and its real world location so that virtual objects can be accurately drawn atop the video of the scene every frame. Depending on the embodiment, registration for a mobile device can be performed periodically and/or by relying on the mobile device&#39;s frame-by-frame tracking ability once a registration is in place. How much of the registration process is performed on the individual user&#39;s mobile device versus how much is performed on a remote server can vary with the embodiment and depend on factors such as the nature and complexity of detection of features, database lookup, and solution calibration. 
       FIGS.  1  and  2    illustrate some of the examples of the presentation of AR graphics and added AR content at an outdoor venue and an indoor venue, respectively.  FIG.  1    illustrates a golf course venue during an event, where the green  120  (extending out from an isthmus into a lake) and an island  110  are marked out for later reference.  FIG.  1    shows the venue during play with spectators present and a user viewing the scene with enhanced content such as 3D AR graphics on the display of a mobile device  121 , where the depicted mobile device is smart phone but could also be an AR headset, tablet, or other mobile device. 
     Some examples of the graphs that can be displayed on a viewer&#39;s mobile device are also represented on the main image. These include graphics such as player information and ball location  101  for a player on the green  120 , concentric circles indicating distances  103  to the hole, ball trajectories  105  with player information  107  on the tee location, and a grid  109  indicating contours and elevation for the surface of the green. Examples of data related to course conditions include the wind indication graphic  111 . 
     The graphics can be overlaid on the image as generated by the mobile device. The user can make selections based on a touchscreen or by indicating within the image as captured by the mobile device, such as pointing in front of the device in its camera&#39;s field of view to indication a position within the image. For example, the viewer could have a zoomed view  130  displayed on the mobile device. The zoomed view  130  can again display graphics such as player info and ball location  131 , concentric distances to the holes  133 , and a contour grid  139 . The viewer could also rotate the zoom view, such as indicated by the arrows. Also indicated in relation to the zoom image are wager markers  141  as could be done by different viewers on mobile devices on a player-to-player basis, along with an indicator of betting result information  143 . 
       FIG.  2    illustrates the indoor venue example of a basketball game, with a viewer with a mobile device  221  providing 3D AR graphics over the image of the mobile device  221 . On the image of the game are shown some example AR graphics, such as player information  251 , ball trajectories  253 , current ball location  255 , and player position and path  257 . Other examples of content include a venue model  260 , player statistics  261 , and a player path  263  in the court. 
       FIG.  3    is block diagram of one embodiment of a system to register a user&#39;s mobile device and provide AR content to the user&#39;s mobile device.  FIG.  3    only illustrates a single mobile device  321 , but, as discussed in more detail below, there can be many (e.g., thousands) such devices operating with the system concurrently. In an example where the user is at a venue, the mobile device  321  could be a cell phone, tablet, glasses, or a head mounted display, for example, and, in the case of multiple users, their respective mobile devices can be of different types. Note that in some embodiments, some of the components of  FIG.  3    can be combined. 
     AR content to display on the mobile device  321 , such as on the 2D camera image of a smart phone as illustrated in the examples of  FIGS.  1  and  2   , can be provided by a content server  323 , where the content can be retrieved from a content database  327  or from a live source, such as in-venue cameras  325 . Content database  327  can be one or both of a local database or a cloud database. Examples of content stored in the database can include things such as 3D terrain contours (i.e., elevations of a green for a golf course) or other venue data that can be acquired prior to the event or provided by venue. The content can also include live data about the event, such as scoring, performance related statistics, environmental data (e.g., weather) and other information. Other content can include live image data from cameras  325  that can supplement a user&#39;s point of view, such as through a “binocular view” to give a closer point of view or to fill in a user&#39;s occlusions, or other live material, such as ball trajectories. The content can be provided from the content server  323  automatically, such as based on previous setting, or directly in response to a request from the mobile device. For example, the user could indicate requested information by touching the display or manually indicating a position such as by placing a finger with the mobile device&#39;s field of view. As the content from the content server  323  is referenced to a real world coordinate system, the mobile device  321  will need a transformation between the real world coordinate system and the mobile device&#39;s coordinate system. 
     The transformation between the mobile device&#39;s coordinate system and the real world coordinate system is provided to the mobile device  321  by registration server  311 . From the mobile device  321 , the registration server  311  receives images and corresponding image metadata. For example, the image metadata can include information associated with the image such as camera pose data (i.e., position and orientation), GPS data, compass information, inertial measurement unit (IMU) data, or some combination of these and other metadata. In some embodiments, this metadata can be generated by an app on the mobile device, such as ARKit running on an iPhone (or other mobile device). Using this data from the mobile device  321  and data in a registration feature database  309 , the registration server  311  determines a transform between the coordinate system of the mobile device  321  and a real world coordinate system. In one set of embodiments, the device to real world coordinate transform can be a set of matrices (e.g., transformation matrices) to specify a rotation, translation, and scale dilation between the real world coordinate system and that of the mobile device. Once that mobile device  321  receives the transformation matrices (or other equivalent data), as the mobile device moves or is oriented differently (a change of pose), the mobile device  321  can track the changes so that the transformation between the mobile device&#39;s coordinate system and the real world coordinate system stays current, rather than needing to regularly receive an updated transformation between the mobile device&#39;s coordinate system and the real world coordinate system from the registration server  311 . The mobile device  321  can monitor the accuracy of its tracking and, if needed, request an updated transformation between the mobile device&#39;s coordinate system and the real world coordinate system. 
     Registration server  311  is connected to a feature database  309 , which can be one or a combination of local databases and cloud databases, that receives content from registration processing  307 , which can be a computer system of one or more processors, that receives input from a number of data sources. The inputs for registration processing  307  includes survey images of multiple views from different positions from one or more survey image sources  301 , such as one or more instrumented cameras. Embodiments can also include coordinates for fiducial points as inputs for the registration processing  307 , where the fiducial points are points with the fields of view of the survey images and that have their coordinates values in the real word coordinate system by use of fiducial coordinate source devices  303 , such as GPS or other device that can provide highly accurate real world coordinate values. In some embodiments, a 3D survey data set can also be used as an input for registration processing  307 , where the 3D survey data can be generated by 3D surveying device  305  and, for many venues, will have previously been generated and can be provided by the venue or other source. 
     To be able to draw 3D graphics accurately over mobile device&#39;s 2D picture of the real world, the registration server  311  needs to know the viewer&#39;s/mobile device  231  position, the way that it is looking (its pose orientation), and camera details such as field of view and distortion. A process for accurately locating the mobile device and generating accurately aligned camera or other mobile device imagery can be broken down into three steps: First, prior to the event, assembling a database of visible features that will be visible from the range of viewer locations; second, when a viewer initially starts using the app, the location of the viewer&#39;s mobile device is determined, and a set of visual features in the mobile device&#39;s field of view is established so that the system can accurately register the graphics as presented on the mobile device to the real world; and third, as the viewer continues to use the app, the mobile device is re-oriented to look at different parts of a scene, tracking features in field of view (such as on a frame-by-frame basis) to maintain an accurate lock between the real world and the augmented reality graphics. 
     To build the registration feature database  309 , survey data is collected for the venue and assembled into a single reference map to serve as a model for the venue. Within the reference map, viewing areas can be identified and planning can be made for the location of temporary structures such as viewing stands, tents, or signage. Reference makers for use as fiducials are also identified. Note that the reference map may not be a literal map, but a collection of data representing the relevant set of features (as described herein). 
     At the venue, prior to event, photos are taken along the line of viewing areas, such as at every 10 feet or 3 meters (or other intervals or distances), and corresponding metadata, such as camera location and orientation, is accurately measured. Multiple cameras can be used, such as three cameras with one looking horizontally in the viewing direction, one camera 45° to the left, and one camera 45° to the right. The photos are taken with high resolution (e.g., 8 megapixel each) and can be saved with high quality JPEG compression, with the imagery and metadata transferred to a central server (e.g., registration processing  307 , registration server  311  or another computing device). The cameras can be connected to a very accurate GPS receiver, compass, inclinometer, and gyroscope, so that the camera locations can be known to within a few inches and their orientation to within a few hundredth of a degree. For improved accuracy, the focal length and distortion for each camera can be pre-measured on an optical bench. To more easily move the camera rig  301  around a venue it could be mounted on a golf cart or a drone, for example. 
     Once the survey images and their metadata are gathered, they are stored on a computer (e.g., registration processing  307 , registration server  311  or another computing device). Surveyed reference points, such as sprinkler locations or visible fiducials placed on reference points, are located prior to taking the photos. The pixel location of fiducial markers can be identified in a variety of the survey images and their 3D coordinates determined via triangulation using the camera parameters, such as discovered from a Structure from Motion (SfM) process. In the processing, these fiducial points are used to refine the measured camera positions and orientations, so that the coordinate system of the photos can be aligned to the real world coordinate system. As described in more detail in the following discussion, given the real world coordinates of the fiducial markers and the SfM coordinates, a transformation is found that maps between the coordinate system of the individual mobile devices and the real world coordinate system.  FIGS.  7 A and  8    respectively illustrate the collection of photos and the use of fiducials, and  FIGS.  9  and  10    respectively present flowcharts for survey preparation and image collection. 
       FIG.  4    is a high-level block diagram of one embodiment of a more general computing system  401  that can be used to implement various embodiments of the registration processing  307 , registration server  311  and/or content server  323 . Specific devices may utilize all of the components shown, or only a subset of the components, and levels of integration may vary from device to device. Furthermore, a device may contain multiple instances of a component, such as multiple processing units, processors, memories, transmitters, receivers, etc. 
     In  FIG.  3   , the registration server  311  and the content server  323  are represented as separate blocks based on their different uses, but it will be understood that these functions can be implemented within the same server and that each of these blocks can be implemented by multiple servers. Consequently, depending on the embodiment, the registration server  311  and the content server  323  can implemented as a single server or as a system of multiple servers. The components depicted in  FIG.  4    includes those typically found in servers suitable for use with the technology described herein, and are intended to represent a broad category of such servers that are well known in the art. 
     The computing system  401  may be equipped with one or more input/output devices, such as network interfaces, storage interfaces, and the like. The computing system  401  may include one or more microprocessors such as a central processing unit (CPU)  410 , a graphic processing unit (GPU), or other microprocessor, a memory  420 , a mass storage d 430 , and an I/O interface  460  connected to a bus  470 . The computing system  401  is configured to connect to various input and output devices (keyboards, displays, etc.) through the I/O interface  460 . The bus  470  may be one or more of any type of several bus architectures including a memory bus or memory controller, a peripheral bus or the like. The microprocessor  410  may comprise any type of electronic data processor. The microprocessor  410  may be configured to implement registration processing using any one or combination of elements described in the embodiments. The memory  420  may comprise any type of system memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), a combination thereof, or the like. In an embodiment, the memory  420  may include ROM for use at boot-up, and DRAM for program and data storage for use while executing programs. 
     The mass storage  430  may comprise any type of storage device configured to store data, programs, and other information and to make the data, programs, and other information accessible via the bus  470 . The mass storage  430  may comprise, for example, one or more of a solid-state drive, hard disk drive, a magnetic disk drive, an optical disk drive, or the like. 
     The computing system  401  also includes one or more network interfaces  450 , which may comprise wired links, such as an Ethernet cable or the like, and/or wireless links to access nodes or one or more networks  480 . The network interface  450  allows the computing system  401  to communicate with remote units via the network  480 . For example, the network interface  450  may provide wireless communication via one or more transmitters/transmit antennas and one or more receivers/receive antennas. In an embodiment, the computing system  401  is coupled to a local-area network or a wide-area network for data processing and communications with remote devices, such as other processing units, the Internet, remote storage facilities, or the like. In one embodiment, the network interface  450  may be used to receive and/or transmit interest packets and/or data packets in an ICN. Herein, the term “network interface” will be understood to include a port. 
     The components depicted in the computing system of  FIG.  4    are those typically found in computing systems suitable for use with the technology described herein, and are intended to represent a broad category of such computer components that are well known in the art. Many different bus configurations, network platforms, and operating systems can be used. 
       FIG.  5    is a high-level block diagram of an embodiment of a mobile device  321  that can be used for displaying graphics of a view at a venue, such as described above. Embodiments of the mobile device can include a smart phone, tablet computer, laptop computer, or other device in which the view of the venue is presented on a display  503 , such as a screen with the graphics content also represented on the display. Other embodiments can include head mounted displays, such as AR headsets or AR glasses, that display the graphics over the view of the venue as watched through the head mounted display. The multiple mobile devices that can be used concurrently with the systems presented here can be various combinations of these different varieties of mobile devices.  FIG.  5    explicitly includes elements of the mobile device  321  relevant to the discussion presented here, but will typically also include additional elements, but that do not enter into the current discussion and are not shown. 
     The embodiment of  FIG.  5    includes a camera  501  and one or more sensors  507  that respectively provide image data and metadata for the image data that can be used in the registration process described above. Mobile devices  321  such as smart phones typically include a camera  501 , such as based on charge coupled devices or other technology, that can provide the image data and also the image of the venue on the mobile device&#39;s display screen, while for a head mounted display, the camera  501  would provide the image data, although it may not be displayed directly to the viewer. The sensors  507  can include devices such as GPS receivers, a compass, and an inertial measurement unit (e.g., accelerometer). The metadata from the sensors  507  can provide information on the pose (location and orientation) of the camera  501  when capturing the image data, but will be within the mobile device&#39;s internal coordinate system that may only loosely be aligned with the real world coordinate system. 
     The mobile device  321  also includes one or more interfaces  505  through which the mobile device  321  can communicate with the registration server  311  and content server  323 . The interface  505  can use various standards and protocols (Bluetooth, Wi-Fi, etc.) for communicating with the servers, including communicating with the registration server  311  for the registration process and with the content server  323  to request and receive graphics and other content. The cellular transceiver  511  can also be used be used to communicate with the registration server  311  and content server  323 , as well as for telephony. 
     A mobile device  321  also includes one or more processors  509 , with associated memory, that are configured to convert the graphics from the content server  323  into the mobile device&#39;s coordinate system based on the transformation between the mobile device&#39;s coordinate system and the real world coordinate system as received from the registration server  311 . The processor(s)  509  can be implemented as ASICs, for example, and be implemented through various combinations of hardware, software, and firmware. The processor or processors  509  can also implement the other functionalities of the mobile device not related to the operations describe here, as well as other more relevant functions, such as monitoring latencies in communications with the servers and adapting the amount of processing for the registration and display of graphics done on the mobile device  321 , relative to the servers, based on such latencies. 
     The display  503  is configured to present the graphics over the view of the venue. In the case of device where the display  503  is a screen (such as a smart phone or tablet), the view of the venue can be generated by the camera  501 , with the graphics also displayed on the screen. In this case, user input (such as related to gamification or requesting specific graphics) can be input by a viewer using the display and/or, in some embodiments, by indicating within the view of the venue from the camera  501 , such as by finding the user&#39;s fingertip within the image and projecting a ray to this location to, for example, touch where a ball will land or to touch an object to place a bet. In a head mounted display  503 , such as AR goggles or glasses, the graphics or other content can be presented over the view of the venue through the mobile device  321 , where the user can make indications within the view. 
       FIG.  6    is a is a flowchart describing one embodiment for the operation of an AR system for providing viewers with AR graphics over views of an event. Beginning at step  601 , the venue is prepared for a survey to collect image mages and fiducial points&#39; coordinates that are supplied to the registration processing  307 . Step  601  is discussed in more detail with respect to  FIG.  9   . The survey images are then collected in step  603 , which is described in more detail with respect to  FIG.  10   . From the data collected is steps  601  and  603 , the registration processing  307  builds a model of the venue, as described further with respect to  FIG.  11   . Steps  601 ,  603 , and  605  are typically performed before the event, although data can also be collected during an event, such as through crowd sourced image data, to refine the model. 
     Before the event, mobile devices  321  are registered with a server system including a registration server  311  at step  607 . This is done by each mobile device  321  sending the registration server  311  image data and metadata, that will be in the coordinate system of the mobile device, to the registration server. For each mobile device  321 , the registration server can then build a transformation for converting positions/locations between the mobile device&#39;s coordinate system to a real world coordinate system. The registration server  311  also sends each mobile device  321  template images with a set of tracking points within each of the template images at step  609 . The template images with tracking points allow for each of the mobile devices  321  to maintain an accurate transformation between the mobile device&#39;s coordinate system and the real world coordinate system as the mobile device changes its pose (i.e., location and orientation). Registration and tracking is described in more detail with respect to  FIGS.  13 A and  13 B . At step  611  a registered mobile device  321  can then request and receive AR content, such as graphics to display of views of an event at a venue, from the content sever  323 . More details about step  611  are provided below with respect to  FIG.  17   . 
       FIG.  7 A  illustrates the collection of survey images by a survey camera at a venue. In this example, the venue is the same as illustrated in  FIG.  1   , but shown as a point cloud  700  generated from features within the venue prior to the event and without spectators. For comparison to  FIG.  1   , the island  710  and green  720  are given reference numbers corresponding to reference numbers  110  and  120  in  FIG.  1   . The individual points of the point cloud  700  correspond to features for use in the registration process as described below. One of the data inputs to the process is the survey data as generated by a survey camera rig  301 . 
       FIG.  7 A  illustrates the collection of multiple images from multiple locations at the venue, where  FIGS.  9  and  10    describes an embodiment for the process to collect these survey images. In  FIG.  7 A , several dozen sets of images collected at specific points, where several of these image collections ( 701 ,  757 ,  759 ,  799 ) at some of these locations are explicitly numbered. The actual process can include additional collections of images, such as in the upper portions of the image, but these are not included in  FIG.  7 A  to avoid the Figure becoming overly complicated. The number of such locations and the number of photos taken will vary based on the specifics of the venue and the event, but as described below, these will typically be collected at positions where viewers are likely to be located and with sufficient density be able to perform an accurate registration process. 
     In the lower portion of  FIG.  7 A  is an expanded view of the collection of images  759  to illustrate the collection more clearly. At the center is the location of the survey camera rig  301  used to collect a set of images, where the survey camera rig  301  can include a single camera or multiple cameras along with equipment to determine the camera location and orientation. The images are represented by a set of N frustums (e.g., truncated pyramids), where a first frustum  759 - 1  and an Nth frustum  759 -N are labeled. The wider base of a frustum (the darker, labelled rectangles) correspond to the 2D image as seen by the camera from its pose when the image is taken and narrow base of a frustum corresponds to the 2D plane of the image collection surface for the camera. The images taken at a given position are taken to overlap and to cover the directions of likely fields of view for users of the mobile devices during the event. 
       FIG.  7 B  is a block diagram of an embodiment of a multi-camera survey camera rig  301  that can be used for taking the survey images. In one embodiment, three cameras with a center camera ( 711   a ) looking horizontally in the viewing direction, one camera ( 711   b ) angled 45° to the left, and one camera ( 711   c ) angled 45° to the right. The cameras can have high resolution (e.g., 8 megapixel each) and can use high quality JPEG compression, with the imagery and metadata transferred over interface  715  to a central server. Depending on the embodiment, the images can be processed on the individual cameras ( 711   a ,  711   b ,  711   c ) or by a separate processing/memory section  713  incorporated into the survey camera rig  301 . The survey camera rig  301  can also include instrumentation  717  to determine the metadata for the orientation and location of the cameras&#39; images. The instrumentation can include a GPS receiver, compass, IMU, and gyroscope, for example, so that the camera locations can be known to within a few inches and their orientation to within a few hundredth of a degree. 
       FIG.  8    illustrates the collection of fiducials at a venue. The venue of  FIG.  8    is the same as for  FIGS.  1  and  7 A  and again shows the same point cloud  700  and reference features of the island  710  and green  720 , but with the image collections (e.g.,  701 ,  757 ,  759 ,  799 ) not shown. The fiducials will be placed prior to, and included in, the collection of survey images, but the image collections are not shown in  FIG.  8    for purposes of explanation. The placement and collection of fiducials are described in more detail with respect  FIGS.  9  and  10   . 
       FIG.  8    shows a number of fiducials within the point cloud  700 , where several examples of the fiducials ( 801 ,  857 ,  859 ,  899 ) are explicitly labelled. As described below, the number and placement of the fiducial will depend on the venue, type of event, and where the survey images are to be collected. The position of the fiducials are determined so that their points&#39; coordinates in the real world coordinate system is well known. This can be done by placing the fiduciaries at locations with well-known coordinates, such as is often the case for features in the venue (e.g., sprinkler locations of a golf course), by accurately measuring the locations of fiduciaries by a GPS or other positioning device, or a combination of these. 
       FIG.  9    is a flowchart of one embodiment of a process for preparing a venue for a survey, providing more detail for step  601  of  FIG.  6   . To organize the collection of survey data, a preliminary model is assembled for the environment of the venue at step  901 , where this can be a 2D or 3D model and can often be based on information available from the venue or bases on a rough survey. Based on this model, regions where viewers will be located during event are identified at step  903 . For example, if the venue is a golf course, viewing arrays are typically around the tee, around the green, and along portions of the fairway. In an indoor venue, such as for a basketball game, the viewing arrays correspond to locations in the stands. At step  905 , the identified viewer locations can be used to plan a path and spacing for points at which to collect the survey images. 
     In step  907 , locations that will be within the images are identified as location for fiducials, where these can be objects in known locations that will be visible in the survey images and which can be used to infer the location and orientation of the survey camera location with high accuracy (i.e., down to fractions of inches and degrees). In the example of a golf course, one choice of fiducial locations can be sprinkler head locations, as these are plentiful, easy to find, and their locations are often carefully surveyed by the venue. To make fiducials easier to locate within the survey image, these can be marked by, for example a white or florescent yellow sphere a few inches in diameter mounted on a stand that lets it be located as a specified height (e.g., an inch above a sprinkler head). In some cases, to improve accuracy, a reference GPS base station in communication with the survey camera rig can be set up at step  909 . 
       FIG.  10    is a flow of one embodiment of a process to collect survey images following the preparation of Described with respect to  FIG.  9    and provides more detail for step  603  of  FIG.  6   . Starting at step  1001 , any wanted fiducial marker are placed for a section of the survey path. Depending on the implementation, this can be all of the fiducial markers for the entire survey or for a section of the survey, with the marked moved from views already photographed to subsequent views as the survey camera rig  301  is moved along the survey path. As discussed above, the survey camera rig  301  can be part of rig of multiple cameras along equipment to determine corresponding metadata for the images. The survey camera rig  301  is moved along the path, such as the planned path from step  905 , collecting images in step  1003 . In the case of a fixed rig of several cameras, at each location the rig can collect a set of images looking in several directions and at different focal lengths, which can be fixed. In terms of instrumentation, the survey camera rig  301  can include an accurate GPS receiver, where this can be referenced to a base station in some embodiments. The GPS receiver can also be integrated with an initial measurement unit, or IMU, with linear and rotational rate sensors, and additionally be integrated with a magnetic compass. Step  1005  records the GPS position and orientation metadata for each of the images. As the images and their metadata are accumulated, the image quality and metadata accuracy can be monitored at step  1007 . Once the images are collected, the fiducial markers can be recovered at step  1009  and the survey imagery and corresponding metadata copied to a server at step  1011 . 
     In some embodiments, the survey images can be augmented by or based on crowd crowd-soured survey images from viewers&#39; mobile devices  321 . For example, users could be instructed to provide images of a venue before or even during an event, taking photos with several orientations from their viewing positions. This can be particularly useful when an event is not held in a relatively compact venue, such as a bicycling race in which the course may extend a great distance, making a formal survey difficult, but where the course is lined with many spectators who could supply survey image data. In some instances, as viewers provide crowd-sourced survey images, the registration process can be updated during an event. For embodiments where crowd-sourced survey images are provided prior to the event, these crowd sourced images can be used along with, and in the same manner as, the survey images collected prior to the event by the camera rig  301 . When the crowd-sourced survey images are provided during the event, they can be combined with the initial survey data to refine the registration process. For example, based on the pre-event survey images, an initial model of the venue can be built, but as supplemental crowd-sourced survey images are received during an event, the feature database  309  and registration process can be made more accurate through use of the augmented set of survey images and the model of the venue refined. This sort of refinement can be useful if the views of a venue change over the course of the event so that previously used survey images or fiducial points become unreliable. 
     In some embodiments, for venues or portions of venues where survey images and fiducials are sparse or absent (e.g., a cycling race), the crowd-sourced survey images and their metadata can be used without the survey images from a camera rig  301  or fiducial point data. The crowd-sourced survey images and their corresponding metadata alone can be used in the same manner as described for the survey images generated by a camera rig  301  and the lack of fiducials from a survey can be replaced by extracting some degree of fiducial point data from the crowd-sourced survey images and their metadata. The model can be generated using crowd sourced images in combination with survey images, using survey images only, or using crowd sourced images only. The images are crowd sourced images as they are provided from the public at large (e.g., those at the venue) and function to divide work between participants to achieve a cumulative result (e.g., generate the model). In some embodiments, the identify and/or number of the plurality of mobile devices used to provide the crowd sourced images are not known in advance prior to the event at the venue. 
     To have accurately generated real world coordinate data for the fiducials, as part of the survey process these locations can be determined by a GPS receiver or other fiducial coordinate source device  303 . In some cases, the venue may already have quite accurate location data for some or all of the fiducial points so that these previously determined values can be used if of sufficient accuracy. 
     In some embodiments, 3D survey data and similar data can also be used as a source data. For example, this can be established through use of survey equipment such as by a total station or other survey device  305 . Many venues will already have such data that they can supply. For example, a golf course will often have contour maps and other survey type data that can be used for both the registration process and also to generate content such as 3D graphics like contour lines. 
     Once the source data is generated, this can be used by the registration processing  307  to generate the feature database  309 . The processing finds detectable visual features in the images, for those that can be detected automatically. The better features are kept for each image (such as, for example, the best N features for some value N), while keeping a good distribution across the frame of an image. For each image, a descriptor is extracted and entered into a database of features and per-image feature location. Post-processing can merge features with closely matching descriptors from multiple images of the same region, using image metadata to infer 3D locations of a feature and then enter it into the feature database  309 . By spatially organizing the database, it can be known what is expected to be seen from a position in direction. Although one feature provides some information about position and orientation, the more features that are available, the more accurate the result will be. When a venue is a constructed environment, such as a football stadium or a baseball park, there will typically be enough known fiducials to determine position and orientation. In more open venues, such as golf course fairway with primarily organic shapes such as trees and paths, additional reference points may need to be collected. 
     Non-distinctive features in the images, such as a tree trunk, edge of a cart path, or the silhouette of trees against the sky, can be correlated across adjacent views to solve for 3D locations and then entered into the feature database  309 . Such features can typically be detected, but often not identified uniquely. However, if where the image is looking is roughly known, it is also roughly known where to expect the features to be located. This allows for their arrangement in space to be used to accurately identify them and to accurately determine a location, orientation, and camera details. The process can also collect distinctive information extracted from the features, such as width of a tree trunk or size of a rock, to help identify the objects and include these in the database. 
     Once the images have been registered, they can be used in conjunction with a 2D venue map to identify spectator areas as 3D volumes. The tracking and registration process can ignore these volumes and not attempt to use features within them as they will likely be obscured. Other problem areas (large waving flags, changing displays, vehicle traffic areas) can similarly be ignored. In some cases, it can be useful to perform a supplemental survey shortly before an event to include added temporary structures that may be useful for registration and also reacquire any imagery that can be used to correct problems found in building the initial feature database  309 . The feature database  309  can also be pruned to keep the better features that provide the best descriptor correlation, are found in a high number of images, and that provide a good distribution across fields of view. 
       FIG.  11    is a flow chart describing one embodiment for processing the imagery in registration processing  307  to generate the data for the feature database  309  from the survey images, fiducial points&#39; coordinates, and 3D survey data. The process of  FIG.  11    is an example implementation of step  605  of  FIG.  6   . The processing can be done offline, with manual operations performed by several people in parallel, and with a mix of automated and manual effort. For the individual collected images, at step  1101  fiducials within the image are identified and the position metadata fine-tuned. Also, within the individual images, at step  1103  various types of macro features (i.e., large scale features identifiable visually be a person) that can be used for registration are identified. At step  1105  the GPS position and orientation metadata for the images are recorded, where the positions can be stored in cartesian coordinates as appropriate for the venue, for example. In addition to camera position and orientation, the metadata can also include camera intrinsic parameters such as focal distance, optical center, and lens distortion properties. Step  1107  looks at adjacent sets of images and identifies features present in multiple images and solves for their 3D location. The feature database  309  is assembled at step  1109 , where this can be organized by viewing location and view direction, so that the registration server  311  can easily retrieve features that should be visible from an arbitrary location and view direction. 
       FIG.  12    is a more detailed flowchart of the process for an embodiment for operation of the registration processing  307  based on a three columned architecture and illustrating how the steps of  FIG.  11    fit into this architecture. Other embodiments may not include all of the columns, such as by not using the third column. In  FIG.  12   , the left most column uses the survey images, possibly including supplemental crowd-sourced survey images to generate descriptors and coordinate data for features. The middle column uses a combination of survey images and fiducial points&#39; coordinates to generate macro feature coordinate data. The right column uses 3D survey data to generate 3D contours. 
     In terms the elements of  FIG.  4   , the inputs (the survey images, fiducial points coordinates, 3D survey dataset) can be received through the network interfaces  450  and the outputs (feature descriptor coordinate data, macro coordinate data, 3D contours) transmitted to the feature database or databases  309  by the network interfaces  450 . The processing steps of  FIG.  12    (e.g.,  1201 ,  1215 ,  1221 ,  1225 ) can be performed by the microprocessor  410 , with the resultant data (e.g.,  1213 ,  1217 ,  1219 ,  1223 ,  1229 ) stored in the memory  420  or mass storage  430 , depending on how the microprocessor stores it for subsequent access. For process operations that may require some degree of manual operation, such  1211 ,  1227 , or  1231 , these can also be performed by microprocessor  410  with manual input by way of the I/O interface  460 . 
     Considering the left most column, the survey images can be acquired as described above with respect to the flows of  FIGS.  9  and  10    and also, in some embodiments, incorporate crowd-sourced images. In some embodiments, Structure-from-Motion (SfM) techniques can be applied to process the images in block  1201 , where SfM is a photogrammetric range imaging technique that can estimate 3D structures from a sequence of images. For example, the COLMAP SfM pipeline or SfM techniques can be used. The resultant output is a set of descriptors and coordinate data for the extracted features. For example, this can be in the form of scale-invariant feature transform (SIFT) descriptors that can be stored in the feature database  309 . The SIFT descriptors can be, for example, in the form of a vector of 128 floating points values that allows for features to be tracked and matched by descriptors that are robust under varying viewing conditions and are not dependent on the features illumination or scale. The output of the structure-from-motion can also include camera pose data from the images for use in the second column of  FIG.  12   . 
     The second column of  FIG.  12    includes inputs of the same survey images as the left column, both directly and through the camera pose data (i.e., position and orientation metadata)  1217 , and of the fiducial points&#39; coordinates. The fiducials within the survey images are labelled in block  1211 , where this can include both automated and manual labelling as described above. The result of the labelling are the fiducial 2D coordinates within the images at block  1213 . 
     The camera pose data obtained from structure-from-motion  1217  will be referenced to a coordinate system, but this is a free floating coordinate system used for the structure-from-motion process and not that of the real world. As the 3D graphics and other content that will be provided to the mobile device  321  needs to be in the same coordinate system as the images, the coordinate system of the camera pose data of structure-from-motion  1217  needs to be reconciled with a real world coordinate system. This is performed in the processing of structure-from-motion to real world solver  1215 . The data inputs to the structure-from-motion to real world solver  1215  are the camera pose data of structure-from-motion  1217 , the fiducial 2D coordinates data  1213 , and the fiducial points&#39; coordinates. The resultant output generated by the structure-from-motion to real world solver is a structure to real world transform  1219 . In some embodiments, operations corresponding to some or all of the additional elements of the middle column of  FIG.  12    can be moved to the registration server  311 . For example, the elements  1221 ,  1223 , and  1225  or their equivalents could be performed on the registration server  311 , in which case the structure-from-motion transformation between the mobile device&#39;s coordinate system and the real world coordinate system would be stored in the feature database  309 . As represented in  FIG.  12   , the additional elements of  1221 ,  1223 , and  1225  are performed prior to the storage of data in the feature database  309 . 
     Considering the structure-from-motion to real world transform  1219  in more detail, structure-from-motion is performed in a normalized coordinate system appropriate for numeric purposes and the camera extrinsic data is expressed in this coordinate system. The transform  1219  is a similarity transformation that maps points from the SfM coordinate system into the target, real world coordinate system. The cameras&#39; coordinate system can be converted to a real world coordinate system based on a combination of a rotation and translation and a scale, rotation, and translation operation. The combination of these can be used to generate a transform matrix between the two coordinates systems. 
     As shown in the embodiment of  FIG.  12   , the registration processing  307  continues on to a transform pose process  1221  to transform the camera poses (their locations and orientations) used during the survey process to the real world coordinate system based on the camera pose from the structure-from-motion  1217  and the structure-from-motion to world transform  1219 . The resultant data output is the camera pose to real world coordinate transformation  1223 , allowing the camera pose in the camera&#39;s coordinate system to be changed into the camera&#39;s pose in the real world coordinate system. 
     The system also performs bundle adjustment  1225  based on the camera pose to world coordinate transformation  1223  data labeled macro 2D feature data  1229  as an input. The labeled macro 2D feature data  1229  is generated by a label macro features process  1227  to assign labels to the large scale macro features, where this can be a manual process, an automated process, or a combination of these, where this is often based on the types of features. Bundle adjustment is a process of, given a set of images depicting a number of 3D points from different viewpoints, simultaneously refining the 3D coordinates describing the scene geometry, the parameters of the relative motion, and the optical characteristics of the cameras employed to acquire the images. The bundle adjustment  1225  can be an optimization process for minimizing the amount of error between differing projections of the images, resulting in the output data of the macro features&#39; coordinate data for storage in the feature database  309 . 
     In embodiments including the third column of  FIG.  12   , a set of 3D contour data is generated from the 3D survey dataset by extracting and name contours process  1231 . This can be a manual process, an automated process, or a combination of these. As noted above, the 3D survey dataset can include existing data provided by the event venue as well as data newly generated for the registration process. 
     As described above with respect to  FIG.  3   , the data from registration processing  307  are features&#39; descriptor and coordinate data, macro-feature coordinate data, and 3D contour data. This data is stored in the feature database  309 , from which the registration server  311  can retrieve these as point feature data, large scale feature data, and shape feature data for use in the registration process. 
     To register a viewer&#39;s mobile device  321 , the registration server  311  receives the position, orientation, and field of view (or pos/orient/fov) data from the mobile device  321 , such as from an API on phone or other mobile device  321 . Prior to sending this data, which serves as metadata for the image data from the mobile device  321 , the GPS and compass on the mobile device will calibrate themselves, this may include prompting the user to get a clearer view of the sky or perhaps move the mobile device through a figure-eight pattern, for example. Typically, this can provide a position within about 5 meters, an orientation within about 10 degrees, and a field of view within about 5 degrees. The camera or other mobile device  321  can grab images, every 5 seconds for example, and perform basic validity checks, and send the image data and image metadata to the server. 
     Once the image data and metadata are at the registration server  311 , the registration server  311  finds distinctive and non-distinctive features within the image and, using image metadata for position and orientation, compares this to expected features in the feature database  309 . For example, the registration server  311  can use distinctive features to refine the position and orientation values, then use this location to identify the non-distinctive features to further solve for the position, orientation, and field of view of the mobile device  321  within the real world coordinate system. On the registration server  311 , the solving problem identifies alignment errors for each feature, where these errors can be accumulated across multiple viewers and used to improve the 3D location estimation of the feature. 
     In some embodiments, the registration server  311  can prompt the user to do a pan left-right for the mobile device  321 . The images from the pan can be captured and used to build up a simple panorama on the registration server  311 . The registration server  311  can then build a pyramid of panorama images at a range of resolution values, find likely tracking points and reference, or “template”, images including the likely tracking points, and sends these to the mobile device  321 . Based on the tracking points and template images, the mobile device  321  can locate, find, and match reference points in image frames quickly on a frame-by-frame basis to get an accurate orientation value for the mobile device  321 . 
     Once the mobile device  321  is registered, it can track the images, maintaining a model (such as a Kalman-filtered model) of the mobile device&#39;s camera&#39;s orientation, where this can be driven by the IMU of the mobile device  321  and tracking results from previous frames. This can be used by the mobile device  321  to estimate the camera parameters for the current frame. The mobile device can access the current set of simple features at their predicted location with a current image, such as by a simple template matching, to refine the estimate. Typically, it is expected that a mobile device  321  may have its orientation changed frequently, but that its location will change to a lesser amount, so that the orientation of the mobile device  321  is the more important value for maintaining graphics and other content locked on the imagery with the real world coordinate system. 
     The active set of simple features can be updated so that the area of view is covered, with simple features being discarded or updated based upon which simple features can be readily found and factors such as lighting changes. In some embodiments, the features can be reacquired periodically and re-solved for location and orientation to account for a viewer moving or due to a drifting of fast tracking values, for example. This could be done on a periodic basis (e.g., every minute or so), in response to the mobile device&#39;s GPS or IMU indicating that the viewer has moved, or in response to the matching of local reference features starting to indicate difficulties for this process. If the mobile device is unable to locate template features within the current image, a more detailed match against the panorama images can be performed, where this can start with the lower resolution images, to reacquire an orientation for the mobile device  321  or determine that the view is obstructed. In response to being unable to locate template features within the current image, the AR graphics and other content may be hidden or, alternately, continued to be displayed using a best guess for the mobile device&#39;s orientation. In some embodiments, the mobile device  321  can provide the user with a visual indication of the level of accuracy for the tracking, so that the user can be trained to pan smoothly and with a consistent camera orientation (i.e., mostly upward), and maintain a view of the scene in which obstructions are minimized. 
       FIGS.  13 A and  13 B  are flowcharts describing embodiments of the registration and tracking process of step  607  and  609  of  FIG.  6   .  FIG.  13 A  describes the process performed by the mobile device  321  and  FIG.  13 B  describes the registration process performed by the registration server  311 . Once a user is at the venue, the user&#39;s phone or other mobile device  321  obtains one or more frames of image data containing from camera  501  along with the image&#39;s corresponding camera position and orientation metadata from the sensors  507 , as described in the preceding paragraphs. Step  1301  of  FIG.  13 A  is the capturing of the one or more images by the mobile device and step  1303  includes the accumulation of the corresponding metadata at the mobile device. Once accumulated and stored in the processors/memory  509 , the image and image metadata can then be sent from the mobile device  321  to the registration server  311  at step  1305  over the interfaces  505  or cellular transceiver  511 . 
     At steps  1307  and  1309 , the mobile device  321  receives the transformation between the mobile device&#39;s coordinate system and the real world coordinate system and the tracking points and template images from the registration server  311 . Before going to steps  1307  in  FIG.  13 A , however,  FIG.  13 B  is discussed as it describes how the received information at steps  1307  and  1309  is generated on the registration server. 
     More specifically,  FIG.  13 B  describes how the data sent from the mobile device  321  at step  1105  is used by the registration server  311  to generate the data received back the mobile device in steps  1307  and  1309 . Starting at step  1351 , the registration server  311  receives the image and image metadata from the mobile device  321  over the network interfaces  450 . Based on the images&#39; metadata, the registration server  311  retrieves the descriptors of expected features at step  1353  from feature database  309  over the network interfaces  450 , where this data can be stored in the memory  420  or mass storage  430 . Starting from the expected positions and shapes of the features in the images, and given the corresponding metadata (position, orientation, field of view, distortion), at step  1355  the registration server  311  locates, to the extent possible, the actual features. From the located features, at step  1357  registration server can adjust the initial measurement of the mobile device&#39;s metadata (camera position, orientation, focal length, distortion) and determine an optimal alignment. The tracked real world position and orientation of the mobile device  321  are then used by the microprocessor  410  of the registration server  311  to calculate the transformation between the mobile device&#39;s coordinate system and the real world coordinate system at step  1359 . The registration server also calculates tracking points and template images for the individual mobile devices  321  at step  1361 , where, as described in more detail below, the tracking points and template images are used by the mobile device to update its transformation between the mobile device&#39;s coordinate system and the real world coordinate system as the mobile device  321  changes pose. The transformation between the mobile device&#39;s coordinate system and the real world coordinate system can be in the form of a set of matrices for a combination of a rotation, translation, and scale dilation to transform between the coordinate system of the mobile device  321  and the real world coordinates. The calculated transformation between the mobile device&#39;s coordinate system and the real world coordinate system and tracking points/template images are respectively sent from the registration server  311  over the network interfaces  450  to the mobile device  321  at steps  1363  and  1365 . 
     Returning now to  FIG.  13 A  and the flow as seen by the mobile device, the mobile device  321  receives the transformation between the mobile device&#39;s coordinate system and the real world coordinate system (step  1307 ) and the tracking points and template images (step  1309 ). Once the registration is complete and the information of steps  1307  and  1309  received, by using this data by the processors/memory  509  the mobile device  321  can operate largely autonomously without further interaction from the registration server as long the tracking is sufficiently accurate, with the internal tracking of the mobile device  321  continuing to operate and generate tracking data such as, for example, on a frame-by-frame basis. 
     At step  1311 , the mobile device  321  aligns its coordinate system with the real world coordinate system based on the transformation between the mobile device&#39;s coordinate system and the real world coordinate system. This can include retrieving, for each frame of the images, tracking position and orientation, converting these to real world coordinates, and drawing 3D graphics content from the content server over the images. This correction can be implemented as an explicit transformation in the 3D graphics scene hierarchy, moving 3D shapes into the tracking frame of reference so that it appears in the correct location when composited with over the mobile devices images. 
     Using the tracking points and template images, the alignment of the device to real world coordinate systems is tracked at step  1313  and the accuracy of the tracking checked at step  1315 . For example, every frame or every few frames, the basic features supplied by the registration process at step  1309  are detected in the mobile device&#39;s camera  501  and verified that they are in the expected location. If the tracking is accurate, the flow loops back to step  1313  to continue tracking. If the reference features cannot be found, or if they are not within a margin of their expected location, the registration process can be initiated again at step  1317  by sending updated image data and metadata to the registration server  311 . Additionally, the mobile device  321  can periodically report usage and accuracy statistics back to the registration server  311 . 
     Although  FIG.  3    explicitly illustrates only a single mobile device  321 , and the flows of  FIGS.  13 A and  13 B  are described in terms of only a single mobile device, in operation the system will typically include multiple (e.g., thousands) such mobile devices and the flows of  FIGS.  13 A and  13 B  can be performed in parallel for each such mobile device. Additionally, the distribution of the amount of processing performed the mobile device relative to the amount of processing performed on the servers can vary based on the embodiment and, within an embodiment, may vary with the situation, such as by the mobile devices or registration servers could monitor the communication speed in real time. For example, if a latency in communications between a mobile device and the servers exceed a threshold value, more processing may be shifted to the mobile devices, while if transmission rates are high additional processing could be transferred to servers to make use of their greater processing power. 
       FIG.  14 A  is a more detailed flowchart of an embodiment for the operation of registration server  311 . The registration server  311  retrieves the output of the three columns from registration processing  307  from the feature database  309  and combines these with the image data and metadata from a mobile device  321  to determine the transformation between the mobile device&#39;s coordinate system and the real world coordinate system. In terms of  FIG.  4   , the inputs (image data and image metadata from the mobile devices  321  and point features, large scale features, and shape features from the feature database  309 ) can be received through the network interfaces  450  and the outputs (the coordinate transformations and tracking points and template images) transmitted to the mobile device  321  by the network interfaces  450 . The processing steps of  FIG.  14 A  (e.g.,  1411 ,  1415 ,  1419 ,  1421 ,  1425 ,  1433 ) can be performed by the microprocessor  410 , with the resultant data (e.g.,  1413 ,  1417 ,  1423 ,  1431 ) stored in the memory  420  or mass storage  430 , depending on how the microprocessor stores it for subsequent access. 
     The point features from the database  309 , such as in the form a descriptor and 3D real world coordinates in the form of scale invariant feature transformation (SIFT) features, and the mobile device image data and image metadata are supplied to processing block  1411  to determine 2D feature transformations, with the resultant output data of 2D and 3D feature transformation pairs  1413 , which can again be presented in a SIFT format. The processing of to find 2D macro features  1415  matches the mobile device&#39;s 2D image data to the 3D large scale features. To find the 2D macro features from the mobile device&#39;s image data, the inputs are the 2D image data and corresponding image metadata from the mobile device  321  and the large scale feature data (macro features and their 3D coordinate data) from the feature database  309 . The processing to find 2D macro features  1415  from the mobile device&#39;s images can implemented as a convolutional neural network (CNN), for example, and generates matches as 2D plus 3D transformation pairs  1417  data for the large scale macro features of the venue. 
     For embodiments that use the 3D survey dataset, shape features extracted from the 3D survey data are combined with the image data and image metadata from the mobile device  321 . The mobile device&#39;s image data and image metadata undergo image segmentation  1421  to generate 2D contours  1423  for the 2D images as output data. The image segmentation can be implemented on the registration server  311  as a convolutional neural network, for example. The 2D contour data  1423  can then be combined with the 3D contour data from the feature database  309  in processing to render the 3D contours to match the 2D contours within the images from the mobile device  321 . 
     A camera pose solver  1419  generates the camera pose for mobile device  321  in real world coordinates  1431  as output data. The camera pose solver  1419  input data are the image data and image data from the mobile device  321 , the 2D plus 3D feature transformation pairs  1413  data, and the macro 2D plus 3D transformation pairs  1417  data. The camera pose solver  1419  can also interact with the rendering of 3D contours and matching with 2D contour processing  1425 . Based on these inputs, the output data is the camera pose of mobile device  321  in the real world coordinates  1431 , which are then used to determine the transform so that the mobile device  321  can align its coordinate system to real world. The processing to calculate the pose offset transform  1433  uses the camera pose in real world coordinates  1431  and the image data and image metadata from mobile device  321 . The device to real world coordinate transform can be a matrix of parameters for a translation to align the origins of the two coordinate systems, a rotation to align the coordinate axes, and a dilation, or scale factor, as distances may be measured differently in the two coordinate systems (e.g., meters in the mobile device  321  whereas measurement for a venue are given in feet). The device to real world coordinate transform can then be sent from the registration server  311  to the mobile device  321  along a set of tracking points and template images. Although described in terms of a single mobile device  321 , this process can be performed concurrently for multiple mobile devices by the registration server. 
       FIGS.  14 B- 14 D  illustrate implementations for the registration of a mobile augmented reality device  321  with a central registration server or servers  311 . In the embodiment of  FIG.  14 A , the implementation sequentially performs each of the elements the registration process where the mobile device  321  sends image data and image metadata to a central registration server  311 , extracts features from the images data, matches features against the feature database, solves for the pose of the mobile device  321 , and sends a device/real world coordinate transformation (either for an initial transformation to align the coordinate systems or to correct/update the transformation) back to the device. As the speed of the response of the registration server  311  can be a factor in a positive user experience, alternate implementations can be used to provide a quicker response time, such as the quick/detailed implementation of  FIG.  14 C  or the pipelined approach of  FIG.  14 D . The presentation of  FIGS.  14 B- 14 D  present the process in terms of three steps (extract features, match features, and solve for pose), it will be understood that alternate embodiments can use additional or different steps. 
     In the approach of  FIG.  14 C , an initial correction is returned to the mobile device  321  followed by a more detail solution for solving the mobile device&#39;s pose. As represented in  FIG.  14 C , the determination and return of an initial correction is shown in the upper sequence, with the more detailed solution in the lower sequence. The upper sequence is similar to  FIG.  14 B  and begins with the mobile device  321  sending image data and image metadata to the registration sever  311 , but now only a subset of features is extracted from the image data by the registration server  311 . As the number of extracted features is reduced, the determination of an initial correction can be performed more quickly than for the full process of  FIG.  14 B . After the subset of features are extracted, the subset is matched against the feature database  309  to determine a quick solve for the mobile device&#39;s pose, with this initial correction then sent from the registration server  311  to the mobile device  321 . The mobile device can then begin an initial alignment of coordinate systems based on the initial correction data. To provide a more detailed solve for the pose of the mobile device  321 , the registration server  311  extracts the remaining features from the image data, matches these against the feature database  309 , and then can refine the quick solve to generate a more detailed solve for the pose of the mobile device  321 . The more detailed correction can then be used by the mobile device  321  to refine the quick result. Although  FIG.  14 C  illustrates the rough solution being determined and sent prior to starting the full registration process, in some embodiments these can overlap, such as beginning to extract the remaining features while the subset of features is being matched against the database. 
       FIG.  14 D  illustrates an extension of the process of  FIG.  14 C  to a pipelined approach, incrementally returning better results as the registration server  311  repeatedly extracts features from the image data, matches each set of extracted features against the feature database  309 , repeatedly solves for the pose of the mobile device  321 , and returns the updated corrections to the mobile device  321  from the registration server  311 . How many features that are found and matched by the registration server  311  before solving and returning an initial solution to the mobile device  321  can be a tunable parameter, as can also be the solution accuracy requirements. For example, the system can adjust the thresholds for the number of features found, matched, and included in the pose solution before returning a solution based on the system&#39;s load to adapt to the number of devices undergoing the registration process. The approach of  FIGS.  14 C and  14 D  provide an early or partial result that may be of lower accuracy than that of  FIG.  14   , but still be sufficient to start operating without the user wait that would result in waiting for the full quality result of the arrangement of  FIG.  14 B . 
       FIG.  15    illustrates the use of multiple mobile devices  321   a ,  321   b ,  321   c ,  321   d , and  321   e  with the registration server  311  and content server  323  The example of  FIG.  15    shows five mobile devices, but the number can range from a single device to large numbers of such devices used by viewers at an event venue. The mobile device can be of the same type or of different types (smart phone, tablet, or AR headset, for example). Each of the mobile devices  321   a ,  321   b ,  321   c ,  321   d , and  321   e  can independently supply the registration server  311  with image data and image metadata as described above for a single mobile device  321 . The registration server  311  can concurrently and independently perform the registration process for each of the mobile devices, providing them with their corresponding transformation between the mobile device&#39;s coordinate system and the real world coordinate system and with their own set of tracking points and reference images. Each of the mobile devices  321   a ,  321   b ,  321   c ,  321   d , and  321   e  can independently request and receive 3D graphics and other content from the content server  323 . Although  FIG.  15    represent the registration server  311  and content server  323  as separate blocks, in an actual implementation each of these can correspond to one or more servers and parts or all of their functions can be combined within a single server. 
     In some embodiments some or all of the mobile devices  321   a ,  321   b ,  321   c ,  321   d , and  321   e  can provide crowd-sourced survey images that can be used by registration processing  307  to supplement or, in some cases, replace the survey images from a survey camera rig  301 . Depending on the embodiment, the crowd-sourced survey images can be one or both of the image data and image metadata supplied as part of the registration process or image data and image data generated in response to prompts from the system. The crowd-sourced survey images can be provided before or during an event. In some cases, such as extended outdoor venue (a golf course or route for a cycling race), there may be activity at the location of some viewers but not others, so that some of the crowd-sourced survey images could be used for assembling the feature database  309  relevant to a location prior to activity at the location, while other crowd-sourced survey images or other data would be relevant to locations of current activity. 
     Once a mobile device  321  has been registered, it can receive 3D graphics and other content for display on the mobile device.  FIGS.  1  and  2    include some example of such content, with  FIG.  16    presenting a block diagram of the distribution of content to user&#39;s mobile devices. 
       FIG.  16    is a block diagram of an embodiment for supplying content to one or more user&#39;s mobile devices.  FIG.  16    explicitly represents two such mobile devices,  321   a  and  321   b , but at an actual event there could be large numbers of such mobile devices at a venue. The mobile devices  321   a  and  321   b  request and receive content from the content server  323 . Although the specifics will vary depending on the venue and the type of event,  FIG.  16    illustrates some examples of content sources, where some examples of content were described above with respect to  FIGS.  1  and  2   . 
     A content database  327  can be used to supply the content server  323  with information such as 3D graphics and other information that can be determined prior to an event, such as player information, elevation contours, physical distances, and other data that can be determined prior to event. Some of this content, such as 3D contours may also be provided from the registration server and the feature database  309 . The content server  323  may also receive live data from the venue to provide as viewer content on things such as player positions, ball positions and trajectories, current venue conditions (temperature, wind speed), and other current information on the event so that live, dynamic event data visualization can be synchronized to the playing surface live action. One or more video cameras  325  at the venue can also provide streamed video content to the mobile devices  321   a  and  321   b : for example, in some embodiments if a user of a mobile device requests a zoomed view or has there is subject to occlusions, the cameras  325  can provide a zoomed view or fill in the blocked view. 
     For some embodiments, the different mobile devices  321   a  and  321   b  can also exchange content as mediated by the content server  323 . For example, the viewers can capture and share content (amplified moments such as watermarked photos) or engage in friend-to-friend betting or other gamification. The viewer can also use the mobile device  321   a  or  321   b  to send gamification related requests (such as placing bets on various aspects of the event, success of a shot, final scores, and so on) and responses from the content server  323  to the internet, such as for institutional betting or play for fun applications. 
       FIG.  17    is a flowchart describing one embodiment of a process for requesting and receiving graphics by a registered mobile device  321 , providing more detail for step  611  of  FIG.  6   . At step  1701  the registered mobile devices  321   a ,  321   b ,  321   c ,  321   d ,  321   e  of  FIG.  15    request graphics content from content server  323 . (The mobile devices  321   a ,  321   b ,  321   c ,  321   d ,  321   e  will have already received the transformation between the mobile device&#39;s coordinate system and the real world coordinate system from the registration server  311 .) The requests for graphics at step  1701  can be based both on direct user input and on automatic requests by a mobile device  321 . For example, as the mobile device has its field of view changed, new graphics can be requested based on the corresponding change in pose, in which case the mobile device can automatically issue a request for graphs appropriate to the new view of the venue. The graphics can also be used based on what is occurring in the view, such as when one set of players in a golf tournament finish a hole and a new set of players start the hole. User input to select graphics can be selected through the display of the mobile device  321 , such as by the touch screen of a smart phone or laptop computer, or by pointing within the field of view of the camera for the mobile device. For example, a viewer may indicate a player&#39;s position within the view to request graphics of information on the player. 
     In step  1703 , mobile devices  321   a ,  321   b ,  321   c ,  321   d ,  321   e  receive from content server  323  their respective graphics to be displayed by the mobile devices  321   a ,  321   b ,  321   c ,  321   d ,  321   e  over a view of the venue, where the graphics are specified by location and orientation in the real world coordinate system. Each of the mobile devices  321   a ,  321   b ,  321   c ,  321   d ,  321   e  can then use processor(s)  509  to convert the graphics into the mobile device&#39;s coordinate system based on the transformation at step  1705 . The transformed graphics are then presented over a view of the venue by display  503  at step  1707 . 
     The discussion to the point has focused on embodiments of augmented reality system using mobile devices, such as augmented reality enabled devices such as mobile phones, headsets, or glasses that are used to enhance a viewer&#39;s experience at an event&#39;s venue. The techniques can also be extended for use at remote locations, such as at home or a sport bar, for example, where the event is viewed on a television in conjunction with a smart television as part of “tabletop” embodiment. 
       FIGS.  18  and  19    illustrate examples of a tabletop embodiment for respective events at a golf course venue and a basketball venue, corresponding to the at-venue embodiments of  FIGS.  1  and  2   . In a tabletop embodiment, in addition to being able to view the event on a television, the views can also view the event on mobile devices, such as a smart phone, with overlaid graphs and also to view graphics on a model of the venue with graphics. 
       FIG.  18    illustrates the same event and venue as  FIG.  1   , but viewed at a remote venue on a television  1800 . The event can again be viewed on the display of a mobile device  1821   a  or  1821   b  with graphics and other AR content displayed along with the view of the event. A tabletop view  1830 , similar to the zoomed view  130  of a model of the view in  FIG.  1    can also be viewed by a head mounted display  1823 . The augmented view can also present content, such as player statistics  1801  or course conditions such as the wind indication graphic  1811 . 
     The tabletop view  1830  can include the graphics as described above for the in-venue view, both on the mobile device  121  and also in the zoomed view  130  of  FIG.  1   . Some examples include player info and ball location  1831 , concentric distances to the holes  1833 , and a contour grid  1839 , as well as gamification graphics such as wager markers  1841 . 
       FIG.  19    illustrates the same event and venue as  FIG.  2   , but viewed at a remote venue on a television  1900 . A viewer can again view the event with augmented reality graphics on a mobile device  1921  with a display screen, the same as those presented above for in-venue viewing, or as a tabletop view  1830  presentation when viewed with an augmented reality head mounted display  1923 . In the tabletop view  1960 , the augmented reality content can again include content such as player statistics  1951  and  1961  described above with respect to  FIG.  2   , along with gamification graphics  1941 . 
       FIG.  20    is a block diagram of elements of a tabletop embodiment. Similar to  FIG.  3   ,  FIG.  20    again illustrates a registration server  2011  and a content server  2023 , along with a mobile device  2021  such as a smart phone or other mobile device with a screen display. These elements can operate much as described above for the corresponding elements of  FIG.  3    and other figures, but where the other elements of  FIG.  3    are not explicitly shown in  FIG.  20   . 
       FIG.  20    also includes a television  2051  for remote viewing of the event, where the television may be connected to receive content from one or both of the registration server  2011  and content server  2023 , receive content by another channel (cable or internet, for example), or a combination of these. The mobile device  321  may also interact with the television  2051  to receive content or transmit control signals, such as to change views or request content.  FIG.  20    further includes a head mounted display  2031  such as an AR headset or AR glasses. The display of the head mounted display  2031  can display the tabletop view  2030 , along with AR graphics. 
       FIG.  21    is flowchart for the operation of tabletop embodiment. As with the in-venue flow of  FIG.  6   , prior to an event a model of the venue is built. At step  2101  the venue is prepared for survey, with the survey images collected at step  2103 . Steps  2101  and  2103  can be as described above with respect to steps  601  and  603  and can be the same as these steps, with the process for in-venue enhanced viewing and the process for remote viewing being the same process. At step  2105  a tabletop model of the venue is built in much the same way as described with respect to step  605 , but additional the model of the venue is built for a tabletop display. In the tabletop view such as  1830  or  1960 , rather than being display over a view of the venue as viewed through a head mounted display of the mobile device or on the display of the mobile device, at a tabletop position at the remote venue a representation of the venue is also presented, with the AR graphics presented over the representation. When viewed with an augmented reality head mounted display  1823  or  1923 , the venue representation with graphics is displayed at a designed location (i.e., a tabletop) within the remote venue. 
     At step  2108  the mobile devices  1821 / 1921  and  1823 / 1923  are register similarly to step  607  of  FIG.  6   , but now the position of where the tabletop view  1830 / 1960  is to be located by the head mounted displays is also determined. This position can be determined by input from the views of the head mounted displays  1823 / 1923  within venue at step  2109 . Although the movements at a remote venue will often be more limited than for in-venue viewing, tracking (similar to step  609 ) is performed at step  2111 , both to accurately display the graphics, but also to maintain the laptop model in its location. At step  2113 , requested graphics are again provided to the views on their mobile devices. 
     According to one set of aspects, a method includes receiving from each of a plurality of mobile devices image data and image metadata, the image metadata including information on the mobile device&#39;s location and orientation within a venue for an event in the mobile device&#39;s coordinate system and retrieving, from one or more databases, point features of the venue in a first coordinate system and locations of a set of fiducials features for the venue in a real world coordinate system. The method further includes building of a model of the venue in the real world coordinate system from the point features of the venue and the locations of the set of fiducials features in the real world coordinate system and generating for each of the mobile devices a corresponding transformation between the mobile device&#39;s coordinate system and the real world coordinate system from the image data and image metadata from each of the mobile devices and the model of the venue in the real world coordinate system. Additionally, the method includes: transmitting to each of the mobile devices the corresponding transformation between the mobile device&#39;s coordinate system and the real world coordinate system; receiving from each to the mobile devices receiving requests for content including graphics to be displayed by the mobile device over a view of the venue as specified by location and orientation in the real world coordinate system; and transmitting to each of the mobile devices the requested content. 
     In other aspects, a system includes a registration server configured to access data from one or more databases and to receive data from and transmit data to a plurality of mobile devices and a content server configured to receive data from and transmit data to the plurality of mobile devices. The registration server is also configured to: retrieve point features of a venue for an event in a first coordinate system and locations of a set of fiducials features for the venue in a real world coordinate system from the one or more databases; for each of the mobile devices, receive image data and image metadata, the image metadata including information on the mobile device&#39;s location and orientation within the venue in the mobile device&#39;s coordinate system; from the point features of the venue and the locations of the set of fiducials features in the world coordinate system, build a model of the venue in the real world coordinate system; from the image data and image metadata from each of the mobile devices and the model of the venue in the real world coordinate system, generate for each of the mobile devices a corresponding transformation between the mobile device&#39;s coordinate system and the real world coordinate system; and transmit to each of the mobile devices the corresponding transformation between the mobile device&#39;s coordinate system and the real world coordinate system. The content server is configured to: for each of the mobile devices, receive requests for graphics to be displayed by the mobile device over a view of the venue as specified by location and orientation in the real world coordinate system; and transmit to each of the mobile devices the requested graphics. 
     Aspects also include a method, comprising: transmitting, from a mobile device to a server system, image data of a venue and image metadata, the image metadata including location information and orientation for the image data in the mobile device&#39;s coordinate system; in response to transmitting the image data and image metadata, receiving at the mobile device a transformation between the mobile device&#39;s coordinate system and the real world coordinate system from the server system; transmitting, from the mobile device to the server system, requests for graphics to be displayed by the mobile device over a view of the venue as specified by location and orientation in the real world coordinate system; receiving at the mobile device the requested graphics from the server system; and displaying by the mobile device of the requested graphs over the view of the venue. 
     Additional aspects include a method that comprises: retrieving by a server from one or more databases point features of a venue for an event in a first coordinate system; retrieving by the server from the one or more databases locations of a set of fiducials features for the venue in a real world coordinate system; receiving by the server of image data and image metadata from a mobile device, the image metadata including information on the mobile device&#39;s location and orientation within the venue in a coordinate system of the mobile device; generating by the server of a transformation between the mobile device&#39;s coordinate system and the real world coordinate system from the image data and image metadata from the mobile device and from the point features of the venue and the locations of the set of fiducials features in the real world coordinate system; generating by the server for the mobile device a set of template images and a set of tracking points within each of the template images configured to allow the mobile device to track an accuracy of the transformation between the mobile device&#39;s coordinate system and the real world coordinate system from the image data and from the point features of the venue; transmitting from the server to the mobile device the transformation between the mobile device&#39;s coordinate system and the real world coordinate system; and transmitting from the server to the mobile device the set of template images and the set of tracking points within each of the template images. 
     More aspects include a system of one or more servers configured to access data from one or more databases, to receive data from and transmit data to a mobile device. The one or more servers are also configured to: retrieve, from the one or more databases, point features of a venue for an event in a first coordinate system and locations of a set of fiducials features for the venue in a real world coordinate system; receive image data and image metadata from the mobile device, the image metadata including information on mobile device&#39;s location and orientation within the venue in a coordinate system of the mobile device; from the image data and image metadata from the mobile device and from the point features of the venue and the locations of the set of fiducials features in the real world coordinate system, generate a transformation between the mobile device&#39;s coordinate system and the real world coordinate system; from the image data and from the point features of the venue, generate for the mobile device a set of template images and a set of tracking points within each of the template images configured to allow the mobile device to track accuracy of the transformation between the mobile device&#39;s coordinate system and the real world coordinate system; transmit to the mobile device the transformation between the mobile device&#39;s coordinate system and the real world coordinate system; and transmit to the mobile device the set of template images and the set of tracking points within each of the template images. 
     Aspects also include a method that comprises: generating image data by a mobile device; generating by the mobile device of image metadata for the image data in a coordinate system for mobile device; transmitting by the mobile device of the image data and the image metadata to one or more servers; subsequent to transmitting the image data and the image metadata, receiving by the mobile device from the one or more servers a transformation between the mobile device&#39;s coordinate system and the real world coordinate system and graphics to be displayed by the mobile device over a view of a venue as specified by location and orientation in the real world coordinate system; converting by the mobile device of the graphics into the mobile device&#39;s coordinate system based on the transformation between the mobile device&#39;s coordinate system and the real world coordinate system; and presenting by the mobile device of the graphics over the view of the venue. 
     Other aspects include a method that includes: generating by a mobile device of image data of a venue and image metadata for the image in a coordinate system for the mobile device; providing image data of the venue and image metadata from the mobile device to a server system; generating by the server system of a transformation between the mobile device&#39;s coordinate system and the real world coordinate system from the image data and image metadata; transmitting the transformation between the mobile device&#39;s coordinate system and the real world coordinate system from the server system to the mobile device; receiving at the mobile device from the server system of graphics to be displayed by the mobile device over a view of the venue; converting by the mobile device of the graphics into the mobile device&#39;s coordinate system based on the transformation; and displaying by the mobile device of the graphics over the view of the venue. 
     Additional aspects include a system having a mobile device configured to: generate image data of a venue and image metadata for the image data in a coordinate system for the mobile device; receive a transformation between the mobile device&#39;s coordinate system and the real world coordinate system; receive graphics to be displayed by the mobile device over a view of the venue specified by location and orientation in the real world coordinate system; convert the graphics into a coordinate system of the mobile device based on the transformation between the mobile device&#39;s coordinate system and the real world coordinate system; and present the converted the graphics over the view of the venue. The system also includes one or more servers configured to exchange data with the mobile device and to: receive the image data of the venue and the image metadata; generate the transformation between the mobile device&#39;s coordinate system and the real world coordinate system from the image data and image metadata; provide the transformation between the mobile device&#39;s coordinate system and the real world coordinate system; and provide the graphics to be displayed over the view of the venue specified by location and orientation in the real world coordinate system. 
     In other aspects, a method includes: generating image data by a camera of a first mobile device; providing image metadata in a coordinate system for first mobile device for the image data by one or more sensors of the first mobile; transmitting the image data and the image metadata from the first mobile device to one or more servers; transmitting a request for graphics to be displayed by the first mobile device over a view of a venue from the first mobile device to one or more servers; receiving at the first mobile device from the one or more servers a transformation between a coordinate system the first mobile device and a real world coordinate system; receiving at the first mobile device from the one or more servers the requested graphics; converting by the first mobile device of the requested graphics into the first mobile device&#39;s coordinate system based on the transformation between the first mobile device&#39;s coordinate system and a real world coordinate system; and presenting the requested graphics over the view of the venue by the mobile device. 
     Additional aspects present a method that includes: receiving, at a server system from each of a plurality of mobile devices, corresponding image data of a venue for an event and corresponding image metadata, the image metadata including information about a location and an orientation of the corresponding mobile device within the venue in a coordinate system of the corresponding mobile device when capturing the image metadata; building by the server system of a model of the venue in a real world coordinate system from the image data and image metadata from the plurality of mobile devices; generating by the server system of a corresponding transformation between each of the mobile device&#39;s coordinate system and the real world coordinate system from the corresponding image data and image metadata of each of the mobile devices and the model of the venue in the real world coordinate system built from the image data and image metadata from the plurality of mobile devices; and transmitting from the server system to each of the mobile devices the corresponding transformation between the mobile device&#39;s coordinate system and the real world coordinate system. 
     More aspects include a system that includes one or more servers configured to access data from one or more databases, to receive data from and transmit data to a plurality of mobile devices. The one or more servers are also configured to: receive, from each of the mobile devices, image data of a venue for an event and image metadata, the image metadata including information on a location and an orientation of the mobile device within the venue in a coordinate system of the mobile device when capturing the image metadata; build a model of the venue in the real world coordinate system from the image data of a venue for an event and image metadata from the plurality of mobile devices; from the image data and image metadata of each of the mobile devices and the model of the venue in the real world coordinate system, generate for each of the mobile devices a corresponding transformation between the mobile device&#39;s coordinate system and the real world coordinate system; transmit to each of the mobile devices the corresponding transformation between the mobile device&#39;s coordinate system and the real world coordinate system; for each of the mobile device, receive requests for graphics to be displayed by the mobile device over a view of the venue as specified by location and orientation in the real world coordinate system; and transmit to each of the mobile devices the requested graphics. 
     Further aspects present a method that includes: receiving, at a server system from each of a plurality of mobile devices, image data of a venue for an event and image metadata, the image metadata including information on a location and an orientation of the mobile device within the venue in a coordinate system of the mobile device when capturing the image metadata; retrieving point features of the venue in a first coordinate system and locations of a set of fiducials features for the venue in a world coordinate system by the server system from the one or more databases; building by the server system of a model of the venue in the world coordinate system from the point features of the venue in the first coordinate system, the locations of the set of fiducials features for the venue in the world coordinate system, and the image data of a venue for an event and image metadata from the plurality of mobile devices; generating by the server system of a corresponding transformation between the mobile device&#39;s coordinate system and the real world coordinate system for each of the mobile devices from the image data and image metadata of each of the mobile devices and the model of the venue in the world coordinate system; and transmitting from the server system to each of the mobile devices the corresponding transformation between the mobile device&#39;s coordinate system and the real world coordinate system. 
     For purposes of this document, reference in the specification to “an embodiment,” “one embodiment,” “some embodiments,” or “another embodiment” may be used to describe different embodiments or the same embodiment. 
     For purposes of this document, a connection may be a direct connection or an indirect connection (e.g., via one or more other parts). In some cases, when an element is referred to as being connected or coupled to another element, the element may be directly connected to the other element or indirectly connected to the other element via intervening elements. When an element is referred to as being directly connected to another element, then there are no intervening elements between the element and the other element. Two devices are “in communication” if they are directly or indirectly connected so that they can communicate electronic signals between them. 
     For purposes of this document, the term “based on” may be read as “based at least in part on.” 
     For purposes of this document, without additional context, use of numerical terms such as a “first” object, a “second” object, and a “third” object may not imply an ordering of objects, but may instead be used for identification purposes to identify different objects. 
     For purposes of this document, the term “set” of objects may refer to a “set” of one or more of the objects. 
     The foregoing detailed description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The described embodiments were chosen in order to best explain the principles of the proposed technology and its practical application, to thereby enable others skilled in the art to best utilize it in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope be defined by the claims appended hereto.