== Google Summer of Code PostGIS Raster Ideas ==


'''1) Implement write support for the PostGIS raster GDAL driver.''' 

 Mentor: Jorge Arevalo (jorgearevalo at libregis.org) or David Zwarg.

 A [http://www.gdal.org/ GDAL] driver allows reading/writing of raster (or images) data from/to formats like TIFF, PNG or JPEG.

 The current GDAL PostGIS raster driver supports reading of PostGIS rasters objects from a PostgreSQL/PostGIS database but does not support writing. The project includes proposing a driver writer design and implementing it. You will familiarize yourself with GDAL-OGR development (one of the most used open source geospatial package), geospatial imagery concepts, open source development tools and code in C.

Might be able to reuse some logic already present in the packaged PostGIS raster2pgsql loader.

'''2) Implement a set of geometry to raster functions'''

    Mentor: Pierre Racine (pierre.racine at sbf.ulaval.ca)

    With the ability to store geometries and rasters in postgis, there is now a gap to fill by implementing geometry to raster algorithms to allow transition from one type to the other.

    1) '''ST_Interpolate''' should be an aggregate taking a set of points (e.g. filtered lidar points) or line geometries (e.g. digitized topo lines) and their associated values and returning a raster representing a surface interpolated from those values. There are numerous methods of [http://en.wikipedia.org/wiki/Interpolation interpolation] and it would nice to have a generic method so we can use all of them, but we’re first targeting [http://en.wikipedia.org/wiki/Bilinear_interpolation bilinear interpolation], which will fill most needs and lay the ground for other methods. For reference, you might want to check an implementation in [http://apps.nrbook.com/empanel/index.html Numerical Recipes (chap. 3)] or in [http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Interpolation/Chapter_main.html#Section_68.3 CGAL]. Converting a point table to a TIN and then to a raster is also a way to go. A Delaunay triangulation can be produced with the [http://www.cs.cmu.edu/~quake/triangle.html Triangle library] (copyright issues should be checked first). See also [http://postgis.17.n6.nabble.com/Voronoi-Dalaunay-function-again-td3522575.html here] and [http://postgis.17.n6.nabble.com/Voronoi-tessellation-td4549913.html here].


    2) '''ST_AsDensity''' takes a point or line geometry coverage and first assign a count of those features to every pixels of a raster coverage and then apply a smoothing filter (using the existing one raster version of neighbour ST_MapAlgebra). [http://www.spatialanalysisonline.com/output/html/Pointdensity.html Density functions]  allow summarizing or simplifying a point or line dataset.

    3) '''ST_Distance''' takes a point or a geometry coverage and compute a raster representing the distance to the nearest geometry. Another function ST_CostDistance() compute the smallest distance to the geometry following a cost raster. This project was [http://trac.osgeo.org/postgis/wiki/PostGIS_Raster_SoC_Idea_2012/Distance_Analysis_Tools proposed by Qing Liu and accepted by the GSoC program].

Want more details? Check the [http://wiki.osgeo.org/wiki/Google_Summer_of_Code_2014 OSGeo GSoC 2014 page] or write to the [http://lists.osgeo.org/mailman/listinfo/postgis-devel PostGIS developer list].

[http://trac.osgeo.org/postgis/wiki/WKTRaster Back to the PostGIS raster project Home Page].