How to generate tile quadkeys between a set of latitude/longitude coordinates

Question

Hello,

I am trying to create an algorithm that could generate all the tile quadkeys at a certain zoom level (say, 13-20) between latitude and longitude coordinates. Let's say I have the top right coordinates, top left, bottom left, and bottom right. How can I generate the tile quadkeys in between?

Any help would be appreciated! Thanks

Answer 1

From the sample code attached to the "Bing Map Tile System" http://msdn.microsoft.com/en-us/library/bb259689.aspx

Use the following in this order:

1. LatLongToPixelXY()
2. PixelXYToTileXY()
3. TileXYToQuadKey()

Answer 2

All the calculations you need are given here: http://msdn.microsoft.com/en-us/library/bb259689.aspx

Quadkeys are just an alternate way of referencing tiles as are defined under the x/y/z referencing system. I find it much easier to work in x/y/z because then, say, you know the distance covered by each tile at a given zoom level and calculate that you need 10 tiles across and 8 tiles down to fill the area - so iterate through the x and y identifiers by the required amount. You can then always convert from x/y/z to quadkey if needed.

Why/what language are you writing this algorithm in? I've probably got some Python code lying around that does it.

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twitter: @alastaira blog: http://alastaira.wordpress.com/

Answer 3

Thanks for the replies!

I am writing it in C# (for wp7). I know python though.

So if I understand correctly, I can convert the lat/longs into PixelX/Ys, convert those into TileX/Ys. Then i just do 2 foreach loops to interate through the X and Ys and increment them by one during each interation? I can then convert them back to quadkeys if necessary.

Answer 4

So if I understand correctly, I can convert the lat/longs into PixelX/Ys, convert those into TileX/Ys. Then i just do 2 foreach loops to interate through the X and Ys and increment them by one during each interation? I can then convert them back to quadkeys if necessary.

Bingo.

Why would you want to do that on a WP7 device though? I assumed that you were trying to generate some sort of tilecache on a server..

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twitter: @alastaira blog: http://alastaira.wordpress.com/

Answer 5

Oh, I meant I am making an wp7 application, but this function would be server-side