polygon to raster GIS

Question

I have a shapefile of India with states (probably as polygons). I want to convert each polygon into equally divided cells ("raster" way), and populate (actually coloring) each cell by a value that would be calculated from an algorithm which is cell's location specific. This should be done for all the cells in the polygon (programmatically) so that at the end I have the shapefile, looking as a thematic (of what my algorithm calculates), raster image. I am not starting any image because the information is actually calculated value from algorithm and not coming from satellite imagery or anything like that.

In other words, it is not a vegetation or elevation thematic but something like population distribution, where each value (color) of cell represents a mean value of population there, showing wholly as a distribution at large scale.

Can any one please help how to do this using any open source application? (both as application and also programmatically using API like sharpmap) Please help

Answer 1

One easy way to do this would be to use Mapnik and its Python binding. See their site for a tutorial on thebasic usage and their XML configuration schema.

Answer 2

I've done this using MapScript (from UMN's Mapserver).

http://mapserver.org/mapscript/index.html#mapscript

It's fairly straight forward and has many bindings (PHP, Ruby, Python, .NET and so forth), but the API is the same across all bindings. Those bindings when I last used it were of varying quality and I'm not up to date on the current quality

Answer 3

The GDAL utilities and scripting would be my choice.

http://www.gdal.org/index.html

I don't quite understand how you are going to decide cell values based on position, but have a look at the following utilites:

http://www.gdal.org/gdal_grid.html

http://www.gdal.org/gdal_rasterize.html

If you can't get the required output from the command line, then the GDAL functions can be scripted (C++ or Python have the most examples).

Answer 4

Hi,

I've done this using python and GDAL by following the instructions outlined here:

http://proj.lis.ic.unicamp.br/webmaps/docs/calc_ndvi/

I hope this helps.

ps. The site is in portugese, so if you don't speak the language you may find Google translate very useful. Good luck.

n