Thursday, February 28, 2013

proj4 used to define custome projection in quantum GIS

Learnt this while trying to get NLCD (National Land Cover Dataset) reprojected to NAD.
In order to define a custom projection in quantum GIS, one has to use the proj4 format:
The final proj4 string: +proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs
The spatial reference information in metadata:
Spatial_Reference_Information:
  Horizontal_Coordinate_System_Definition:
    Planar:
      Map_Projection:
        Map_Projection_Name: Albers Conical Equal Area
        Albers_Conical_Equal_Area:
          Standard_Parallel: 29.500000
          Standard_Parallel: 45.500000
          Longitude_of_Central_Meridian: -96.000000
          Latitude_of_Projection_Origin: 23.000000
          False_Easting: 0.000000
          False_Northing: 0.000000
      Planar_Coordinate_Information:
        Planar_Coordinate_Encoding_Method: row and column
        Coordinate_Representation:
          Abscissa_Resolution: 30.000000
          Ordinate_Resolution: 30.000000
        Planar_Distance_Units: meters
    Geodetic_Model:
      Horizontal_Datum_Name: North American Datum of 1983
      Ellipsoid_Name: Geodetic Reference System 80
      Semi-major_Axis: 6378137.000000
      Denominator_of_Flattening_Ratio: 298.257222


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