Get XY value from TiledMapService Layer Tile

Question

I have an ESRI TiledMapService layer and I have attached an event handler to the TileLoaded. Given the level, row, and column, how can I get the envelop of the tile in map coordinates? I'm using the ESRI Silverlight API...

What I am trying to do: I have a polygon (in the same coordinates of the TiledMapServiceLayer) and I want to examine each tile as it comes in and cut out the pixels of the tile that intersect with the polygon.

Any help would be great!

Answer 1

You need the following information about the TilingSchema:
LOD's
Tile origin
Tile size

With this information, calculate the envelope of a tile is a simple mathematical calculation.
Look at the following picture:

Here’s some math you can use to find any tile:

Column = Floor((Point of interest X – Tile origin X) / (Resolution of Level * TileSize))

and

Row = Floor((Tile origin Y – Point of interest Y) / (Resolution of Level * TileSize))

The opposite:

Point of interest X = Column * Tile Size * Resolution of Level + Tile origin X

and

Point of interest Y = Tile origin Y - Row * Tile Size * Resolution of Level

This is the Upper Left of the tile.
For the Bottom Right:

Bottom Right X = Point of interest X + Tile Size * Resolution of Level

and

Bottom Right Y = Point of interest Y - Tile Size * Resolution of Level

Good luck!