|22||22|| A one raster version of ST_MapAlgebra already exist. We now need a two raster version. This version is much more complicated to implement as it must not only takes into account nodata values but also on-the-fly reprojection of non aligned rasters and multiple possibilities for the resulting extent when the two rasters do not have the same extent. It is also possible, but complicated, to optimize the algorythm in order to fill many areas as a chunck of data instead of pixel by pixel. The project includes reviewing the proposed algorythm and implementing it. You will familiarize yourself with PostGIS development (the most used open source geospatial database), geospatial imagery concepts, open source development tools and code in C and PL/pgSQL.