Importing data: Difference between revisions

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To view a raster map, add it to the Layer Manager with the grid-like button with a (+), to add a vector map to the Layer Manager use the button with lines and points on it to the right of the add raster map button. The left hand button in the Map Display window will re-render the map if needed.
To view a raster map, add it to the Layer Manager with the grid-like button with a (+), to add a vector map to the Layer Manager use the button with lines and points on it to the right of the add raster map button. The left hand button in the Map Display window will re-render the map if needed.


The "computation region" is a very important concept in GRASS and is distinct from the "display window" you see in the Map Display window. You can read about it in the {{cmd|rasterintro}} help page. You can set the computation region and cell resolution to match a specific map with the {{cmd|g.region}} module.
The "[[computational region]]" is a very important concept in GRASS and is distinct from the "display window" you see in the Map Display window. You can also read about it in the {{cmd|rasterintro}} help page. You can set the computational region and cell resolution to match a specific map with the {{cmd|g.region}} module.


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Revision as of 20:36, 3 December 2011

Getting your data into GRASS

GRASS supports many common GIS formats, and many uncommon ones too.

The primary import/export tool is called GDAL/OGR. It is the Rosetta Stone of the free GIS world:


Create a new location for your data with the correct map projection using the Location Wizard on the main startup screen^, then in the menus:

Raster formats:  File → Import raster data using GDAL
Vector formats:  File → Import vector data using OGR

Typically GDAL/OGR will automatically detect the file format for you.

  • [^] You must create a new GRASS location for each map projection you will work with or import data from. If you want the data reprojected into something else you'll have to create that target map projection in a location and pull them into there with r.proj and v.proj, or use GDAL's gdalwarp or ogr2ogr command line tools.
[read more about this on the projectionintro help page]


(v.in.ogr could too, but it's not as smooth)


After the map has been imported you can add it to the display layer list in the Layer Manager window. You will most likely want to right click on the map in the layer list and select "Zoom to selected map(s)". Otherwise when you go to view the map you could be far away and just see a white display canvas.

To view a raster map, add it to the Layer Manager with the grid-like button with a (+), to add a vector map to the Layer Manager use the button with lines and points on it to the right of the add raster map button. The left hand button in the Map Display window will re-render the map if needed.

The "computational region" is a very important concept in GRASS and is distinct from the "display window" you see in the Map Display window. You can also read about it in the rasterintro help page. You can set the computational region and cell resolution to match a specific map with the g.region module.

After importing your data you need to run "g.region -p rast=your_map" or "g.region -p vect=your_map" to set the region bounds/zoom to match that of the newly imported map. Be careful with the region resolution when doing this with vector maps, you may have to run "g.region -a res=" to clean that up and keep it reasonable (for example 2000x2000 rows and columns).

External links

Bulk data import

  • wxGUI menu tools


Modules

Raster

Vector and points

Data formats