Image Tile

Description

For cached image services, the tile resource represents a single cached tile for the image. The image bytes for the tile at the specified level, row, and column are directly streamed to the client. If the tile is not found, an HTTP status code of 404 (Not found) is returned.

Tile interpretation

There are four types of tiles: map, elevation, raster, and multidimensional transposed raster.

Map tiles (introduced at ArcGIS 10.1) represent rendered map images, typically in JPEG or PNG. Elevation tiles (introduced at ArcGIS 10.3) represent elevation data and are stored as limited error raster compression (LERC) tiles. Raster tiles, introduced at ArcGIS 10.8.1, represent image tiles with meaningful pixel values for analysis, not just for rendering. They are stored as LERC2D, JPEGPLUS, or JPGPNG tiles.

Introduced at ArcGIS Enterprise 11.0, transposed multidimensional tiles of the raster tiles use LERC compression only. Raster tiles are available if the image service uses ArcObjects11 or ArcObjectsRasterRendering as the service provider. Multidimensional transposed raster tiles, introduced at ArcGIS 11.0 as a subtype of raster tiles, are hypercubic image tiles representing the specific variables over all the dimensions. It is created for optimizing performance when accessing pixel values across all multidimensional slices rather than for visualization at different map scales. So, the multidimensional transposed raster tiles only have one level and the level should always be 0 when requesting a such tile. There must be a "variable" parameter in the request too.

In terms of topology, elevation tiles differ from normal map tiles in two ways:

• When the service specifies a tile size of 2 pixels (rows/columns), elevation tiles actually contain 2 pixels in each dimension.
• Pixel values for each elevation tile are sampled with an offset of -0.5 * resolution relative to the matching map tile.

For a tile size of 4 by 4 pixels, these properties result in the following arrangement for a colocated map tile and elevation tile:

Sample locations of colocated map and elevation tiles are shown.

This arrangement allows the elevation samples (the pixels of the elevation tile) to be used directly as height values for the vertices of a regular-grid 3D mesh, and for the collocated map tile to be used as a texture for that mesh.

Derive tile extent from tile ID

Given the following notations:

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Service Extent (serviceExt): {xmin, ymin, xmax, ymax}
Tile Origin (origin): {x, y}
Tile Width and Height (tileSize): {cols, rows}
Each LOD (lod): {level, resolution, scale}
Tile ID (tileId): {level, row, column}
Tile Extent (tileExt): {xmin, ymin, xmax, ymax}
Level (lod): LODs[tileID.level]

Multidimensional transposed raster tiles share the tileInfo with normal image tiles in general, but the tile width (cols ) and height (rows ) properties should use the ones under transposeInfo .

Tile extent can be derived using the following formulas, which applies to both map and elevation tiles:

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tileExt.xmin = tileId.column * tileSize.cols * lod.resolution + origin.x;
tileExt.xmax = tileExt.xmin + tileSize.cols * lod.resolution;
tileExt.ymin = tileId.row * tileSize.rows * lod.resolution + origin.y;
tileExt.ymax = tileExt.ymin + tileSize.rows * lod.resolution;

For more information about tiled elevation services, see ArcGIS for Developers documentation.

Request parameters

Example usage

The following request URL is used to access a map for the Toronto cached service:

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https://sampleserver6.arcgisonline.com/arcgis/rest/services/Toronto/ImageServer/tile/13/2990/2289

The following request URL demonstrates requesting a transposed image tile from a multidimensional image service with transposed raster tiles.

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https://myServer/arcgis/rest/services/myService/ImageServer/tile/0/2/2?variable=myVariableName