Changes between Version 20 and Version 21 of WKTRasterGSoC


Ignore:
Timestamp:
03/08/12 12:02:06 (13 years ago)
Author:
pracine
Comment:

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  • WKTRasterGSoC

    v20 v21  
    55'''1) Implement write support for the PostGIS raster GDAL driver.'''
    66
    7  Mentor: Jorge Arevalo (jorge.arevalo at deimos-space.com)
     7 Mentor: Jorge Arevalo (jorge.arevalo at deimos-space.com) or David Zwarg.
    88
    99 A [http://www.gdal.org/ GDAL] driver allows reading/writing of raster (or images) data from/to formats like TIFF, PNG or JPEG.
    … …  
    1313
    1414
    15 '''2) Two rasters version of the ST_MapAlgebra SQL function'''
     15'''2) An optimized version of the two rasters ST_MapAlgebra SQL function'''
    1616
    1717 Mentor: Pierre Racine (pierre.racine at sbf.ulaval.ca)
    … …  
    2020 [http://www.quantdec.com/SYSEN597/GTKAV/section9/map_algebra.htm Map algebra] allows the creation of a new raster as a mathematical (or logical) function of one or two other rasters. e.g. raster3 = (raster1 + raster2) / 2. This is a very common raster operation in the GIS world.
    2121
    22  A two rasters version of the ST_MapAlgebra SQL function would allow a PostGIS user to create a new raster coverage as a function of two existing one with a simple SQL query. e.g.: SELECT ST_MapAlgebra(rast1, rast2, "(rast1 + rast2) / 2") FROM coverage1, coverage2 WHERE ST_Intersects(rast1, rast2)
     22 A two rasters version of the ST_MapAlgebra SQL function already exist. It allows a PostGIS user to create a new raster coverage as a function of two existing one with a simple SQL query. e.g.: SELECT ST_MapAlgebra(rast1, rast2, "(rast1 + rast2) / 2") FROM coverage1, coverage2 WHERE ST_Intersects(rast1, rast2). The extent of the resulting raster can be equivalent to the extent of the FIRST, the SECOND, the INTERSECTION or the UNION of both raster.
    2323
    24  A one raster version of ST_MapAlgebra already exist in PostGIS. To have a complete set of operators, 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.
     24 The current implementation compute the new raster one pixel at a time. It is possible, but complicated, to optimize the algorythm in order to fill many areas as a chunck of data instead of pixels by pixels. 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.
     25
    2526
    2627'''3) Implement a set of geometry to raster functions'''