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| − | {{Content Tree|HEADER=QGIS Tutorial|NAME=QGIS tutorial}}
| + | #redirect[[GRASS region]] |
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| − | {{typed|text=g.region}} is a very important module because it manages the boundary definitions for
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| − | geodata. Changing the settings means that you modify several parameters of a region:
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| − | * geographical projection (e.g. UTM, Latitude-Longitude, Gauss-Krueger, etc),
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| − | * geographical extension, i.e. the North/South/East/West limits of the area covered,
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| − | * number of columns and number of rows for the data,
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| − | * resolution, i.e. the extension divided by the number of rows (N-S resolution), respectively (E-W resolution).
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| − | How do we use it? One of several possibilies is to use the GRASS Shell. Open the Toolbox click on {{mitem|text=Modules List → GRASS Shell}}.
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| − | '''Synthax'''
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| − | *{{typed|text=g.region [rast=name ] [vect=name ] [res=value ] -p -l}}
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| − | '''Parameters'''
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| − | *{{typed|text=[rast=name]}}= Set region to match this raster map
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| − | *{{typed|text=[vect=name]}}= Set region to match this vector map
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| − | *{{typed|text=[res=value]}}= Grid resolution 2D (both north-south and east-west)
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| − | '''Flags'''
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| − | *{{typed|text=-p}}= Print the current region
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| − | *{{typed|text=-l}}= Print the current region in lat/long using the current ellipsoid/datum
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| − | '''Why care about the region?'''
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| − | The region defines the extension and geometric resolution (pixel size) of the data on
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| − | which most GRASS (raster) commands work. If the region is set to a smaller extension
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| − | than that of the map you are working on, display and results of raster processing
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| − | commands will only show the portion of the map that is contained in that region.
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| − | {{attention|text= In short, this means that whatever command you use in GRASS, it is always applied '''only to the data in the current region.''' So always keep an eye on the region settings!}}
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| − | [[category:Introduction to Quantum GIS]]
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