what is the TMSElevationLayer format spec?

Hi,

I saw that you have added elevation to your ReadyMap globe! (e.g. http://demo.pelicanmapping.com/rmweb/webgl/tests/elevation.html). Stunning! I was wondering if you could help me out how to make such a TMSElevationLayer myself? I can work with GDAL and I can code in python. Are there specs for this type of dataset?

To explain why I want to do this: my interest is in planetary data such as topography and imagery from the planet Mars.

Thanks in advance,

Jelmer

Hi Jelmer,

Currently the elevation is being served out by our ReadyMap server product ( http://readymap.com/ ) and it's a bit of a two step process.

The actual elevation data on the server is available using the TMS specification ( http://wiki.osgeo.org/wiki/Tile_Map_Service_Specification ) in tiff format.  If you are familiar with our osgEarth C++ library this is what we use to access elevation data in the readymap.earth demo.  ReadyMap takes care of doing things like edge matching across tiles so you don't see seams, etc.

Currently it isn't possible for Javascript/WebGL to load these tif files to get the elevation postings.  To get around this, we've added a capability to ReadyMap Server to translate the tiff elevation tiles to JSON.  For example, the url:
http://readymap.org/readymap/tiles/1.0.0/9/0/0/0.tif returns the the original tif
http://readymap.org/readymap/tiles/1.0.0/9/0/0/0.tif?json=true Tells the server to generate JSON data from the tif.

The format of the returned JSON is fairly simple.  It specifies the width (int) height (int) and a data property which is an array of floats organized by rows with position [0,0] being in the lower left of the heightfield.

To use elevation data with a server other than ReadyMap you'll need to provide a similar web service that returns JSON elevation data.  If you know some GDAL and Python it shouldn't be too difficult to set something up.

Thanks!

Jason

Hi Jason,

Thanks for all the info. I will start looking into it soon.

Cheers, Jelmer