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This section provides more background about Nearmap’s Panorama Tile Interface.

There is complexity involved in how panorama tiles are arranged, and this section serves as background information to help understand the sample code that is provided below. 

Nearmap Panorama imagery is an orthorectified mosaic. Because it is created by combining many images, metadata that is normally associated with oblique imagery (such as pose and calibration), is not available. All the metadata available for panorama imagery is described under Getting a List of Surveys by Date for a Location.

Foreshortening Effect

Panorama tiles cover the same area as a vertical tile with the same coordinates. If visualised at the same size (256x256 px), panorama tiles look distorted (stretched vertically). This is why we recommend that the client applications display panorama tiles at 256px (width) x 192 px (height).

The compensation for the foreshortening effect needs to be done on the client. Theoretically, the best resize ratio for zoomed-in imagery is cos(45°), which yields images being 181 pixels high. Nearmap chose to use 192 px in the MapBrowser application as it is convenient ratio.

Important Tiling Parameters

The following terms are useful for understanding panorama tiles:

TermDescription
Tile Storage WidthThe width of the image in pixels as it is stored.
Tile Storage HeightThe height of the image in pixels.
Tile Display WidthThe width of the tile as it should be displayed.
Tile Display HeightThe height of the tile as it should be displayed in order to compensate for the foreshortening effect.
Tile Orientation

The direction in which the imagery in the tile is pointing. E.g.  " East Up" means that the top edge of the tile is due East.

The images accompanying each orientation below demonstrate how tiling works using the "X,Y" format. To provide compatibility for the older web-mapping frameworks, the tiles are rotated for orientations other than Vertical and North. When representing them on the screen, the client implementation should arrange the tiles according to the appropriate tiling scheme, as shown below.

Whilst the position X=0,Y=0 on the screen may move, the physical location of that tile is the same for all tiling schemes. The origin tile (X=0,Y=0) is always just west of Greenland, no matter the orientation.

Vertical


AttributeValue
Tile Storage Width256px
Tile Storage Height256px
Tile Display Width256px
Tile Display Height256px
Tile OrientationNorth Up

North 


AttributeValue
Tile Storage Width256px
Tile Storage Height256px
Tile Display Width256px
Tile Display Height192px
Tile OrientationNorth Up

South


AttributeValue
Tile Storage Width256px
Tile Storage Height256px
Tile Display Width256px
Tile Display Height192px
Tile OrientationSouth Up

East


AttributeValue
Tile Storage Width256px
Tile Storage Height256px
Tile Display Width256px
Tile Display Height192px
Tile OrientationEast Up

West


AttributeValue
Tile Storage Width256px
Tile Storage Height256px
Tile Display Width256px
Tile Display Height192px
Tile OrientationWest Up
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