GRASS and MapServer: Difference between revisions
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* You need to have GDAL with OGR and GRASS support for this to work. Note, that in this [http://grass.itc.it/start.html example] the maps are first exported to shapefiles. This is no longer necessary, as the maps can be accessed directly with OGR. | * You need to have GDAL with OGR and GRASS support for this to work. Note, that in this [http://grass.itc.it/start.html example] the maps are first exported to shapefiles. This is no longer necessary, as the maps can be accessed directly with OGR. | ||
* Usually GRASS layers have no names and the layer number is used in DATA. However, it is possible that they do have names. This can happen for example when importing files with v.in.dxf, as the module keeps the dxf-file layer names and stores them into the GRASS vector. The layer names, if such there are, can be found in <tt>/path/to/grassdb/mapset/location/vector/vectorname/dbln</tt>, or with <code>ogrinfo -ro /path/to/grassdb/mapset/location/vector/vectorname/dbln</code>. Why this is so important is because if there are layer names defined, these layers cannot be accessed through the layer number with OGR. They ''have'' to be accessed through the layer name. | * Usually GRASS layers have no names and the layer number is used in DATA. However, it is possible that they do have names. This can happen for example when importing files with v.in.dxf, as the module keeps the dxf-file layer names and stores them into the GRASS vector. The layer names, if such there are, can be found in <tt>/path/to/grassdb/mapset/location/vector/vectorname/dbln</tt>, or with <code>ogrinfo -ro /path/to/grassdb/mapset/location/vector/vectorname/dbln</code>. Why this is so important is because if there are layer names defined, these layers cannot be accessed through the layer number with OGR. They ''have'' to be accessed through the layer name. | ||
==Examples and useful links== | ==Examples and useful links== | ||
Revision as of 12:43, 18 May 2007
GRASS maps from mapfiles
MapServer needs a mapfile containing the information, how to create the maps. Examples of these can be found, so here you'll find GRASS specific information.
Raster Maps
A shor example of a layer definition to access a GRASS raster:
LAYER NAME "Example" TYPE RASTER STATUS ON DATA "/path/to/grassdb/location/mapset/cellhd/example" CLASS NAME "Example" # You need to have a class definition in the layer END END
Notes:
- The rasters are limited to values form 0 to 255, the values over this are interpreted as 255. Rescale (
r.rescale) your maps when necessary. - You really need to have a CLASS in your layer, otherwise no data will be shown. An empty class is quite fine to show the whole map.
Vector Maps
A short example of a layer definition to access a GRASS vector:
LAYER
NAME "Example"
TYPE LINE
STATUS ON
CONNECTIONTYPE OGR
CONNECTION "/path/to/grassdb/mapset/location/vector/example/head"
DATA "1" # Layer number
CLASS # You need to have a class definition; otherwise nothing is shown on the map
NAME "Example"
COLOR 155 155 0
END
END
Notes:
- You need to have GDAL with OGR and GRASS support for this to work. Note, that in this example the maps are first exported to shapefiles. This is no longer necessary, as the maps can be accessed directly with OGR.
- Usually GRASS layers have no names and the layer number is used in DATA. However, it is possible that they do have names. This can happen for example when importing files with v.in.dxf, as the module keeps the dxf-file layer names and stores them into the GRASS vector. The layer names, if such there are, can be found in /path/to/grassdb/mapset/location/vector/vectorname/dbln, or with
ogrinfo -ro /path/to/grassdb/mapset/location/vector/vectorname/dbln. Why this is so important is because if there are layer names defined, these layers cannot be accessed through the layer number with OGR. They have to be accessed through the layer name.
Examples and useful links
- Example of GRASS with MapServer.
- UMN Mapserver homepage