Changes between Version 28 and Version 29 of WKTRasterTutorial01


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Timestamp:
Jun 11, 2010, 8:56:57 AM (11 years ago)
Author:
pracine
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  • WKTRasterTutorial01

    v28 v29  
    9696The -t option specify the table in which we want to load the raster coverage.
    9797
    98 Similar to shp2pgsql.exe, the -s option is required to specify the spatial reference system ID. In this case the raster are in "WGS 84" having the SRID number 4326. Unlike some GIS software, PostGIS does not support on the fly reprojection so that we cannot do operations on table stored with different spatial reference systems. As we could see, the caribou point layer was in "NAD 83/Quebec Lambert" and the SRTM images are in "WGS 84". We will have to deal with this problem later.
     98The -s option, identical to shp2pgsql.exe one, is required to specify the spatial reference system ID. In this case the raster are in "WGS 84" having the SRID number 4326. Unlike some GIS software, PostGIS does not support on the fly reprojection so that we cannot do operations on table stored with different spatial reference systems. As we could see, the caribou point layer was in "NAD 83/Quebec Lambert" and the SRTM images are in "WGS 84". We will have to deal with this problem later.
    9999
    100100The -k option specify the size of the tiles we want to load in PostGIS. Every input raster will be splitted into 100x100 tiles. This dimension is a good compromise allowing efficient raster/vector analysis. It is better if the size of the tiles is a divider of size of each raster. Otherwise the last colomns and rows of tiles from each raster will be filled with nodata values. This might have an impact on performance but not on the result since WKT Raster analysis functions ignore nodata values.
     
    106106}}}
    107107
    108 The result of the gdal2wktraster.py command is a 1.8 GB .sql file produced in 1 minute on my brand new Lenovo X201 labtop (Intel Core i5, 1.17 GHz, 3 GB or RAM :-).
     108The result of the gdal2wktraster.py command is a 1.8 GB .sql file produced in about one minute (on my brand new Lenovo X201 labtop - Intel Core i5, 1.17 GHz, 3 GB or RAM :-).
    109109
    110110The same way we loaded the caribou point sql command file, we will load this sql file using "psql":