Abstract:
A computer system for continuously panningoblique images. More particularly, the computer system uses a methodology whereby separate oblique images are presented in a manner that allows a user to maintain an understanding of the relationship of specific features between different oblique images when panning.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent application claims priority to the provisional patent application identified by U.S. Ser. No. 60/898,990, filed on Feb. 1, 2007, the entire content of which is hereby incorporated herein by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The presently claimed and disclosed invention(s) relate to oblique images and methods for continuously panning the same. More particularly, the presently claimed and disclosed invention(s) use a methodology whereby separate obliquely captured images are panned in a continuous fashion. 
       BACKGROUND OF THE ART 
       [0003]    In the remote sensing/aerial imaging industry, imagery is used to capture views of a geographic area and be able to measure objects and structures within the images as well as to be able to determine geographic locations of points within the image. These are generally referred to as “geo-referenced images” and come in two basic categories:
       1. Captured Imagery—these images have the appearance they were captured by the camera or sensor employed.   2. Projected Imagery—these images have been processed and converted such that they confirm to a mathematical projection.       
 
         [0006]    All imagery starts as captured imagery, but as most software cannot geo-reference captured imagery, that imagery is then reprocessed to create the projected imagery. The most common form of projected imagery is the ortho-rectified image. This process aligns the image to an orthogonal or rectilinear grid (composed of rectangles). The input image used to create an ortho-rectified image is a nadir image—that is, an image captured with the camera pointing straight down. It is often quite desirable to combine multiple images into a larger composite image such that the image covers a larger geographic area on the ground. The most common form of this composite image is the “ortho-mosaic image” which is an image created from a series of overlapping or adjacent nadir images that are mathematically combined into a single ortho-rectified image. 
         [0007]    When creating an ortho-mosaic, this same ortho-rectification process is used, however, instead of using only a single input nadir image, a collection of overlapping or adjacent nadir images are used and they are combined to form a single composite ortho-rectified image known as an ortho-mosaic. In general, the ortho-mosaic process entails the following steps:
       A rectilinear grid is created, which results in an ortho-mosaic image where every grid pixel covers the same amount of area on the ground.   The location of each grid pixel is determined from the mathematical definition of the grid. Generally, this means the grid is given an X and Y starting or origin location and an X and Y size for the grid pixels. Thus, the location of any pixel is simply the origin location plus the number of pixels times the size of each pixel. In mathematical terms: Xpixel=Xorigin+Xsize×Columnpixel and Ypixel=Yorigin+Ysize×Rowpixel.   The available nadir images are checked to see if they cover the same point on the ground as the grid pixel being filled. If so, a mathematical formula is used to determine where that point on the ground projects up onto the camera&#39;s pixel image map and that resulting pixel value is then transferred to the grid pixel.       
 
         [0011]    Because the rectilinear grids used for the ortho-mosaic are generally the same grids used for creating maps, the ortho-mosaic images bear a striking similarity to maps and as such, are generally very easy to use from a direction and orientation standpoint. 
         [0012]    However, since they have an appearance dictated by mathematical projections instead of the normal appearance that a single camera captures and because they are captured looking straight down, this creates a view of the world to which we are not accustomed. As a result, many people have difficulty determining what it is they are looking at in the image. For instance, they might see a yellow rectangle in the image and not realize what they are looking at is the top of a school bus. Or they might have difficulty distinguishing between two commercial properties since the only thing they can see of the properties in the ortho-mosaic is their roof tops, where as most of the distinguishing properties are on the sides of the buildings. An entire profession, the photo interpreter, has arisen to address these difficulties as these individuals have years of training and experience specifically in interpreting what they are seeing in nadir or orthomosaic imagery. 
         [0013]    Since an oblique image, by definition, is captured at an angle, it presents a more natural appearance because it shows the sides of objects and structures—what we are most accustomed to seeing. In addition, because oblique images are not generally ortho-rectified, they are still in the natural appearance that the camera captures as opposed to the mathematical construction of the ortho-mosaic image. 
         [0014]    This combination makes it very easy for people to look at something in an oblique image and realize what that object is. Photo interpretation skills are not required when working with oblique images. Oblique images, however, present another issue. Because people have learned navigation skills on maps, the fact that oblique images are not aligned to a map grid, like ortho-mosaic images, makes them much less intuitive when attempting to navigate or determine direction on an image. When an ortho-mosaic is created, because it is created to a rectilinear grid that is generally a map grid, the top of the orthomosaic image is north, the right side is east, the bottom is south, and the left side is west. This is how people are generally accustomed to orienting and navigating on a map. But an oblique image can be captured from any direction and the top of the image is generally “up and back,” meaning that vertical structures point towards the top of the image, but that the top of the image is also closer to the horizon. 
         [0015]    However, because the image can be captured from any direction, the horizon can be in any direction, north, south, east, west, or any point in between. If the image is captured such that the camera is pointing north, then the right side of the image is east and the left side of the image is west. However, if the image is captured such that the camera is pointing south, then the right side of the image is west and the left side of the image is east. This can cause confusion for someone trying to navigate within the image. Additionally, because the ortho-mosaic grid is generally a rectilinear grid, by mathematical definition, the four cardinal compass directions meet at right angles (90-degrees). But with an oblique image, because it is still in the original form the camera captured and has not been re-projected into a mathematical model, it is not necessarily true that the compass directions meet at right angles within the image. 
         [0016]    Because in the oblique perspective, you are moving towards the horizon as you move up in the image, the image covers a wider area on the ground near the top of the image as compared to the area on the ground covered near the bottom of the image. If you were to paint a rectangular grid on the ground and capture it with an oblique image, the lines along the direction the camera is pointing would appear to converge in the distance and the lines across the direction of the camera is pointing would appear to be more widely spaced in the front of the image than they do in the back of the image. This is the perspective view we are all used to seeing—things are smaller in the distance than close up and parallel lines, such as railroad tracks, appear to converge in the distance. By contrast, if an ortho-mosaic image was created over this same painted rectangular grid, it would appear as a rectangular grid in the ortho-mosaic image since all perspective is removed as an incidental part of the ortho-mosaic process. 
         [0017]    Because a rectilinear grid is used to construct an ortho-mosaic image and the ortho-mosaic images are manufactured to provide a consistent perspective (straight down) it is possible to create the appearance of a continuous, seamless image by simply displaying such images adjacent to one another, or by overlapping them. Such an appearance allows users to remain oriented when navigating between images since the appearance and orientation of a road, building, or other feature remains very similar from one image to the next. 
         [0018]    Because oblique images are not grid aligned and can be captured from any direction a feature on one image will not look the same on another image. This is due to several factors:
       The oblique perspective means that image pixels are not aligned on a rectangular grid but are aligned to the perspective that matches the perspective the camera has captured.   The image pixels on an oblique image cannot measure the same size on the ground due to the perspective of the image. The area of ground covered by the pixels in the foreground of the image is smaller than the area of ground covered in the background of the image. Features in the foreground of an image will be a different size in the background of another image.   The effect of building lean varies from image to image.   The direction an edge of a feature travels across an image, such as the edge of a road or building, will vary between images.   The captured portion of a feature will vary between images. For example: a particular image may contain the entire side of a building due to the head-on position of the capturing camera, but another image only captures a portion of the same side due to the capturing camera being at an angle relative to that side.       
 
         [0024]    Because of these issues, the common practice in the industry is to provide oblique imagery as a series of individual images within which the user can pan. To see beyond the limits of an image the user needs to cause another image to be loaded; they can then pan within that image. This invention details a means to allow continuous panning of oblique images such that the above limitations are overcome. 
       SUMMARY OF INVENTION 
       [0025]    This invention allows for separate obliquely captured images to be panned in a continuous fashion. In one embodiment, the presently disclosed and claimed invention is directed to a sequence of instructions stored on at least one computer readable medium for running on a computer system capable of displaying and navigating oblique imagery. The sequence of instructions includes:
       instructions for displaying a pixel representation of a primary oblique image, the primary oblique image being part of a set of adjacent oblique images that represent an area of interest;   instructions for panning within the primary oblique image;   instructions for detecting a transition event of the primary oblique image;   instructions for selecting at least one adjacent secondary oblique image from the set of oblique images corresponding to a supplied location coordinate; and   instructions for displaying the primary oblique image and the at least one adjacent secondary oblique image on the same display such that the features in the adjacent primary and secondary oblique images are aligned on the display.       
 
         [0031]    In one embodiment, the sequence of instructions stored on the at least one computer readable medium further comprising instructions for translating at least the primary and secondary oblique images&#39; pixel coordinates into location coordinates. 
         [0032]    The transition event can be detected in a variety of manners. For example, the instructions for detecting a transition event may include instructions for (1) detecting the edge of the primary oblique image, (2) detecting the approach of an edge of the primary oblique image, or (3) detecting a pre-selected distance or number of pixels from the edge of the primary oblique image. 
         [0033]    A variety of factors or selection criteria can be used to select the at least one secondary oblique image. For example, a current direction of travel or panning can be used to select at least one secondary oblique image, or a relative position of the supplied location coordinate within the secondary oblique image can be used to select at least one secondary oblique image. In addition, the instructions for selecting an adjacent secondary oblique image from the set of oblique images can be adapted to select multiple adjacent secondary oblique images that correspond to multiple location coordinates, and the instructions for displaying the primary and secondary oblique images on the same display can also include instructions for displaying multiple adjacent secondary oblique images on the same display. 
         [0034]    In one embodiment, the oblique images are aerial oblique images. However, it should be understood that the oblique images can be other types of images, such as medical images, or architectural images. 
         [0035]    The sequence of instructions can also further comprise instructions for causing a secondary oblique image to be a primary oblique image, as well as instructions for permitting a user to cause a secondary oblique image to be a primary oblique image. 
         [0036]    In another version, the presently disclosed and claimed invention is directed to various methods. One of the methods is directed to using a sequence of instructions for displaying and navigating oblique imagery, In one version, the method comprises the steps of:
       displaying a pixel representation of a primary oblique image on a display of a computer system, the primary oblique image being part of a set of oblique images representing an area of interest;   panning within the primary oblique image;   detecting a transition event; and   displaying the primary oblique image and at least one adjacent secondary oblique image on the same display such that the features in the primary and adjacent secondary oblique images are aligned on the same display.       
 
         [0041]    In another version, the invention is directed to a method for configuring a computer system for displaying oblique images representative of adjacent areas on a display. The method comprises the step of:
       making a set of instructions on a computer readable medium accessible to a processor of a computer system, the set of instructions including instructions for:   displaying a pixel representation of a primary oblique image on a display of a computer system, the primary oblique image being part of a set of oblique images representing an area of interest;   panning within the primary oblique image;   detecting a transition event; and   displaying the primary oblique image and the at least one adjacent secondary oblique image on the same display such that the features in the primary and at least one secondary oblique images are aligned on the same display.       
 
         [0047]    In yet another version, the present invention is directed to a method for enhancing the ability of user(s) to display and navigate oblique imagery on a display of a computer system. The method comprises the step of:
       selling and distributing a set of instructions for:   displaying a pixel representation of a primary oblique image on the display of the computer system, the primary oblique image being part of a set of oblique images representing an area of interest;   panning within the primary oblique image;   detecting a transition event; and   displaying the primary oblique image and the at least one adjacent secondary oblique image on the same display such that the features in the present and at least one oblique images are aligned on the same display.       
 
         [0053]    In yet another version, the invention is directed to a method for configuring a computer system having a display for displaying oblique images representative of adjacent areas. The method comprises the step of:
       providing access to a set of instructions stored on a computer readable medium for installation on a computer readable medium associated with the computer system, the set of instructions including instructions for:   displaying a pixel representation of a primary oblique image on the display of the computer system, the primary oblique image being part of a set of oblique images representing an area of interest;   panning within the primary oblique image;   detecting the approach of an edge of the primary oblique image; and   displaying the primary oblique image and the at least one adjacent secondary oblique image on the same display such that the features in the primary and at least one secondary oblique images are aligned on the same display.       
 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0059]      FIG. 1  is a schematic diagram of the hardware forming an exemplary embodiment of a computer system constructed in accordance with the present invention. 
           [0060]      FIG. 2  is a pictorial representation of a Master Image utilized in accordance with the present invention. 
           [0061]      FIG. 3   a  is a pictorial representation of a primary oblique image and a secondary oblique image with an edge indicator consisting of a grayscale secondary oblique image and a Reference Indicator displayed. 
           [0062]      FIG. 3   b  is a pictorial representation of  FIG. 3   a  after the location common to the two images has been changed. 
           [0063]      FIG. 4  is an illustration of an exemplary software/function flow chart of a method for continually panning oblique images. 
       
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY DISCLOSED AND CLAIMED INVENTION 
       [0064]    Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction, experiments, exemplary data, and/or the arrangement of the components set forth in the following description or illustrated in the drawings. 
         [0065]    The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for purpose of description and should not be regarded as limiting. 
         [0066]    The presently claimed and disclosed invention(s) relate to oblique images and a computer system and methods for panning the same in a continuous fashion. 
       Terminology 
       [0000]    
       
         
           
             Area of Interest—an area represented by a set of adjacent oblique images. 
             Master Image—an oblique, orthogonal, or nadir image that is used as a reference for organizing other images in the set. 
             Primary oblique image—a displayed oblique image that can be considered “in front of” the other displayed images. The primary oblique image can also be a master image. 
             Secondary oblique image—an oblique image that is not a Primary oblique image or a master image, but is referenced by a primary oblique image or a master image. 
             Transition—an act of visually changing the primary oblique image into a secondary oblique image and a secondary oblique image into a primary oblique image on a display of a computer system. This can include, and is not limited to: fading images; and directly replacing images. 
             Transition Event—An event that is detected to cause a Transition to take place. The Transition Event can include, but is not limited to: the act of Panning; or a user action such as a mouse click. 
             Navigation—an act of determining what image to display and what portion of an image to display based upon a set of coordinates. 
             Panning—an act of obscuring a currently displayed portion of an image and/or revealing a previously hidden portion of an image involving a visual shifting of the image. 
             Reference Indicator—A visual effect that is used to indicate a common area of interest between two or more images. 
             Edge—an extreme boundary of an image; typically having a top, a right side, a bottom, and a left side of the image. 
             Edge Indicator—A visual effect used to indicate the edge of an image. This definition can include, but is not limited to: rendering a portion of an image, or the entire image, in such a way as to distinguish it from another image (for example, converting an image to grayscale); the use of an arrow glyph to point to the image edge. 
             Feature—One or more captured objects in an image. Features can be used to maintain reference when a user is transitioning between images. 
             Computer System—a system or systems that are able to embody and/or execute the logic of the processes described herein. The logic embodied in the form of software instructions, or firmware may be executed on any appropriate hardware which may be a dedicated system or systems, or a personal computer system, or distributed processing computer system. 
             Computer Readable Medium—a device that can be read either directly or indirectly by a processor of a computer system. Examples of Computer Readable Mediums include an optical storage device, a magnetic storage device, an electronic storage device or the like. 
           
         
       
     
       DETAILED DESCRIPTION  
       [0081]    Referring now to the drawings, and in particular to  FIGS. 1 ,  2  and  3 , shown therein and designated by a reference numeral  10  is an exemplary computer system constructed in accordance with the present invention. 
         [0082]    Preferably, the computer system  10  is distributed, and includes a host system  12 , communicating with one or more user devices  14  via a network  16 . The network  16  can be the Internet or other network. In either case, the host system  12  typically includes one or more servers  18  configured to communicate with the network  16  via one or more gateways  20 . When the network  16  is the Internet, the primary user interface of the computer system  10  is delivered through a series of web pages, but the primary user interface can be replaced by another type of interface, such as a Windows-based application. This method is also used when deploying the computer system  10  in a stand-alone environment such as a kiosk. 
         [0083]    The network  16  can be almost any type of network although Internet and Internet  2  networks are preferred because of the wide support of their underlying technologies. The preferred embodiment of the network  16  exists in an Internet environment, which means a TCP/IP-based network. It is conceivable that in the near future, the preferred or other embodiments, may wish to use more advanced networking topologies. 
         [0084]    The servers  20  can be networked with a LAN  30 . The gateway  20  is an entity responsible for providing access between the LAN  30  and the network  16 . The gateway  20  can also be used as a security means to protect the LAN  30  from attack from external networks such as the network  16 . 
         [0085]    The LAN  30  network can be based on a TCP/IP network such as the Internet, or it can be based on another underlying network transport technology. The preferred embodiment uses an Ethernet network with TCP/IP because of the availability and acceptance of underlying technologies, but other embodiments may use other types of networks such as Fibre Channel, SCSI, Gigabit Ethernet, etc. 
         [0086]    As discussed above, in one preferred embodiment, the host system  12  includes the servers  18 . The configuration of the server hardware will depend greatly upon the requirements and needs of the particular embodiment of the computer system  10 . Typical embodiments, including the preferred embodiment, will include multiple servers  18  with load balancing to increase stability and availability. It is envisioned that the servers  18  will include database servers and application/web servers. The database servers are preferably separated from the application/web servers to improve availability and also to provide the database servers with improved hardware and storage. 
         [0087]    The user devices  14  can be any number and type of devices. The most typical scenario of the user device  14  involves a user  32 , using a computer  34  with a display  36 , keyboard  38 , and mouse  40 . The display  36  can be a single monitor or multiple adjacent monitors. Typically, the user device  14  uses a type of software called a “browser” as indicated by a reference numeral  42  to render HTML/XHTML content that is generated when requesting resources from a source, such as the host system  12 . In the preferred embodiment, the computer system  10  is designed to be compatible with major Web Browser vendors (Microsoft Internet Explorer, Netscape Navigator, and Opera). Other embodiments may wish to focus on one particular browser depending upon the common user base using the computer system  10 . 
         [0088]    The user devices  14  can also be implemented as a portable device such as a laptop computer  50  (or handheld computer); a cellular telephone  52  with a micro or embedded Web Browser; a Portable Digital Assistant  54  (PDA) capable of wireless network access; a pen-based or tablet computer  56 . In another embodiment, the user device  14  can be a cable box  60  or other similar device for viewing through a display  62  or television. Current embodiments of computer system  10  can also be modified to use any of these or future developed devices. 
         [0089]    The computer system  10  is designed in this way as to provide flexibility in its deployment. Depending upon the requirements of the particular embodiment, the Engine could be designed to work in almost any environment such as a desktop application, a web application, or even simply as a series of web services designed to communicate with an external application. 
         [0090]    The hardware and system software are designed with two key concerns; flexibility and scalability. Although some specifics for software and hardware components may be mentioned herein, it will be understood that a wide array of different components could be substituted, such as using different database vendors or even replacing the databases with XML-based document stores. 
         [0091]    When the computer system  10  is used to execute the logic of the processes described herein, such computer(s) and/or execution can be conducted at a same geographic location or multiple different geographic locations. Furthermore, the execution of the logic can be conducted continuously or at multiple discrete times. 
         [0092]    In general, the computer system  10  is capable of displaying and navigating oblique imagery. An oblique image can be represented by a single pixel map, or by a series of tiled pixel maps that when aggregated recreate the image pixel map. 
         [0093]    The computer system  10  will be described by way of example utilizing aerial images. However, it should be understood that the computer system  10  can use other types of images, such as medical images, or architectural images. 
         [0094]    The computer system  10  includes one or more computer readable medium storing instructions for displaying a pixel representation of one or more master image  100  ( FIG. 2 ), one or more primary oblique image  102  and one or more secondary oblique image  104   a - d . The master image(s)  100  is used as a reference for organizing other images in the set, and as shown in  FIG. 2  may represent an area of interest including the primary oblique image(s)  102  and the secondary oblique image(s)  104   a - d . The computer readable medium can be a part of the host system  12 , the user devices  14  or combinations thereof. 
         [0095]    As shown in  FIG. 2 , in a preferred embodiment, the secondary oblique images  104   a - d  overlap a portion of the primary oblique image  102 , such that the overlapping portions of the primary oblique image  102  and secondary oblique images  104  a-d represent the same features of the area of interest. Thus, the primary oblique image(s)  102  and the secondary oblique image(s)  104   a - d  are part of a set of adjacent oblique images cooperating to represent the area of interest or a portion of the area of interest. 
         [0096]    The computer system  10  also includes instructions for (1) displaying a pixel representation of the primary and secondary oblique image on the display  36 . (2) panning within the primary oblique image  102  as indicated by arrows  105   a - d , (3) detecting a transition event of the primary oblique image  102 , (4) selecting at least one adjacent secondary oblique image  104   a - d  from the set of oblique images corresponding to a supplied location coordinate, and (5) displaying the primary oblique image  102  and the at least one adjacent secondary oblique image  104   a - d  on the same display  36  such that the features in the adjacent primary oblique image  102  and secondary oblique images  104   a - d  are aligned on the display  36 . The instructions typically run on a combination of the user devices  14  and the host system  12 . 
         [0097]    The master image  100 , primary oblique image  102 , and secondary oblique image  104   a - d  can be any type of images that have location coordinates or a measuring system stored with or associated with the images. For example, the master image  100 , primary oblique image  102 , and secondary oblique image  104   a - d  can be medical images, architectural images or aerial images. The computer system  10  uses one or more databases or servers  18  (see  FIG. 1 ) to store the master image  100 , primary oblique image  102 , and secondary oblique image  104   a - d  in an organized format. The master image  100 , primary oblique image  102 , and secondary oblique image  104   a - d  can use any color space, and be stored in any industry supported file format, such as TIFF, JPEG, TARGA, GIF, BMP, ECW or the like. 
         [0098]    As described hereinabove, panning oblique images in a continuous manner is fraught with problems and unlikely to provide a useable means of navigation using the current state of the art. Therefore, in order to allow continuous panning of oblique images a new process must be performed. Such an improved and unique process is described and claimed herein and preferably uses, generally, the following considerations:
       The use of a particular portion of the master image  100  to generate one or more geographic locations that are subsequently used to determine a set of oblique images representing the locations.   The use of geographic locations to determine the positioning of one or more secondary oblique images  104   a - d  relative to a primary oblique image  102  to ensure that at least one feature in the primary oblique image  102  is displayed on the secondary oblique image  104   a - d.      The use of visual effects to distinguish an edge of the primary oblique image  102  from any secondary oblique images  104   a - d.      The use of visual effects to indicate where on a primary oblique image  102  and secondary oblique image  104   a - d  the point of interest is located.   The use of a Transition Event to cause a transition to take place between one or more primary oblique images  102  and one or more secondary oblique images  104   a - d.      The simultaneous display of one or more primary oblique image  102  and/or secondary oblique images  104   a - d  or portions of those images.       
 
         [0105]    In practice, the methodology disclosed and claimed herein, consists of multiple steps and data transformations that can be accomplished by one of ordinary skill in the art given the present specification. Either instructions running on the host system  12  or the instructions running on the user devices  14  can detect transition event(s). 
         [0106]    Referring to  FIG. 4 , the first step  200  in handling continuous panning with oblique images is to obtain a relevant geographic location. Once the geographic location is obtained, a set of images representing that location is then obtained, which is the second step  202 . The images can be obtained from the database servers  18  discussed above. The relevant geographic location can be obtained internally, through calculating a position based upon a mathematical formula, or through an external entity, such as a database or user input. In the preferred embodiment, a user indicates an initial geographic location. Subsequent locations are mathematically calculated using image boundaries and other Transition Events. 
         [0107]    The third step  204  is to make a determination of which image from the obtained set best represents the geographic location and make that image the primary oblique Image  102  ( FIG. 2 ). Once the primary oblique Image  102  has been determined one or more Transition Events are determined. In some cases, the computer system  10  acts immediately, for example, on a Transition Event to determine and display secondary oblique images  104   a - d  ( FIG. 2 ) as described below. The transition events can take a variety of forms, such as but not limited to:
       a specific portion of a primary oblique image  102  is calculated to be displayed (“front loading”), or is displayed.   an edge of the primary oblique image  102  or a pre-selected distance or number of pixels from the edge of the primary oblique image  102 .   defined by the user either ahead of time or though some action on the user&#39;s part in “real time”.   A region of the display area not covered by a primary oblique image  102 .       
 
         [0112]    The fourth step  206  is to display the primary oblique image  102 ; whereas the fifth step  208  is to determine and display the secondary oblique images  104   a - d . Usually, secondary oblique Images  104   a - d  are displayed when the primary oblique image  102  doesn&#39;t provide sufficient coverage for the area of interest; but this is not a requirement. When secondary oblique Images  104   a - d  are provided the following steps are taken:
       A geographic location (e.g. a supplied location coordinate) is chosen that is common to both the primary oblique image  102  and a set of secondary oblique images  104   a - d.      A determination of the best secondary oblique image  104   a - d  for that location is made based on algorithmic selection. The algorithmic selection is made based upon a variety of factors, such as one or more selection criteria. If multiple selection criteria are used, the selected selection criteria can be combined either directly (indicating which are in or out of the selection set) or with predetermined weighting factors which indicate which selection criterioin is more important to the selection process. These factors or selection criteria include, but are not limited to: the location of the secondary oblique image  104  (e.g., the geographic location) or the location coordinates contained in the secondary oblique image, the direction from which the secondary oblique image  104  was taken, i.e., the orientation of the secondary oblique image, the ground sample distance of the pixels within the secondary oblique image  104 , image type, the date and/or time the secondary oblique image was captured, the distance from the edge of the location coordinate within the secondary oblique image  104 , the relative position of the supplied location coordinate within the secondary oblique image, the current direction of travel or panning in relation to the secondary oblique image, the nearness of orientation of the secondary oblique image to the primary oblique image, the size of the secondary oblique image, the capture spectra of the secondary oblique image, the image quality of the secondary oblique image, the nearness of metadata information of the secondary oblique image to the metadata information of the primary oblique image, or the vertical position of the location on the secondary oblique image  104 . Which selection criteria or factors to use and how to combine them is predetermined based on the use of the system  10  and the needs of the users of the system  10 .       
 
         [0115]    The best secondary oblique image  104   a - d  is displayed in such a way that one or more common geographic locations on both images are displayed adjacent to each other.
       An Edge Indicator  209  is displayed to show where the primary oblique image  102  ends and the secondary oblique image begins  104   a - d.          
 
         [0117]    If one secondary oblique image  104   a - d  also doesn&#39;t provide sufficient coverage, the Step  208  is repeated for those areas lacking sufficient coverage until there is sufficient coverage. 
         [0118]    The sixth step  210  is to wait for a Transition Event to be triggered. The seventh step  212  is to transition images when a Transition Event is triggered. The user triggers a Transition Event by performing an action that indicates they wish to view a previously hidden portion of an oblique image. There are two ways of satisfying this request:
       1. Scroll the primary oblique image  102  and use secondary oblique Images  104   a - d  as needed to provide sufficient coverage as aforementioned.   2. Cause a new image to be the primary oblique image  102 , position the image appropriately and provide sufficient coverage as needed with secondary oblique Images  104   a - d  as aforementioned.       
 
         [0121]    The display of a new primary oblique image  102  can be accomplished through several techniques. Some, but not all of these techniques are listed below. In the preferred embodiment, the gradual transitioning method is preferred.
       Draw the new primary oblique image  102  over the existing images with no transitions.   Perform a rollback transition where the old primary oblique image  102  appears to be rolled to the side and the newly exposed area is filled with the new primary oblique image.   Gradually transition by fading-out (make less visible) the old primary oblique image  102  and simultaneously fade-in (make more visible) the new primary oblique image  102 .       
 
         [0125]    The purpose of transitioning the primary oblique images  102  is to allow the user to visually maintain a clear sight of the image features they are using for geographic referencing. 
         [0126]    There is a special case of panning that makes use of the currently displayed images through the manipulation of the common geographic location between a primary oblique image  102  and secondary oblique image  104   a - d . It is helpful, but not necessary, to display the Reference Indicator  209  to assist the user in determining where on the images the common locations are. Through the manipulation of the Reference Indicator  209 , or some other means, the common location can be changed causing the displayed images to be updated to maintain the adjacent display of the common location. Due to the nature of oblique images the act of displaying the common location will cause panning to occur, obscuring or revealing portions of an oblique image. 
         [0127]    Thus, in use, the computer system  10  starts with the primary oblique image (i.e., the primary oblique image  102 ) that has location information, such as a geographic position, and as the user causes the primary oblique image  102  to pan across the display  36  and reaches a transition event, such as the edge of the primary oblique image  102 , the instructions running on the computer system  10  automatically determine which secondary oblique image  104   a - d  lies along the edge of the primary oblique image  102  and opens the secondary oblique image  104   a - d . Then, the instructions running on the computer system  10  position the secondary oblique image  104   a - d  on the display such that the features in the adjacent primary oblique image  102  and secondary oblique images  104   a - d  are aligned on the display. 
         [0128]    Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be obvious to those skilled in the art that certain changes and modifications may be practiced without departing from the spirit and scope thereof, as described in this specification and as defined in the appended claims below.