Thursday, 6 April 2017

How to define correctly the Grass region in Qgis


I know that my question could be pretty basic for some of you. I am trying to learn GRASS. I have some raster layers and a vector file in EPSG 32614. Using the grass plugin I defined a new map set, defined a region using the limits of my raster layers.


enter image description here


enter image description here


I succesfully imported both the vectors and the raster in to grass. When I try to run r. cost I have the following error:



Raster map is in different zone (14) than current region (0)


Unable to open raster map


Nevertheless, the metadada of my raster and vector layers are in 32614 (UTM zone 14N). The grass region settings tool tell me this :


enter image description here


I looked in to this question


Raster map in different zone () than region ()


But It does not tell how ti fix the problem. I would appreciate any hint on the matter. I have the same problem working with 2.1 64 bits standalone and also in Lisboa 32 bits standalone working under win 7 64 bits.


Thanks in advance


Gerardo



Answer




When using GRASS GIS, you need to understand the notions of LOCATION, MAPSET and REGION (GRASS GIS: quickstart or GRASS LOCATION and MAPSET in the QGIS user Manual)



A LOCATION is defined by its coordinate system, map projection and geographical boundaries... It is important to understand that each projection stays in its own LOCATION


Each LOCATION can have many MAPSETs. Each MAPSET is a LOCATION's subdirectory.



The REGION is different, it can be seen as a working window for processing rasters (it has nothing to do with a simple zoom function) in a MAPSET (the projection is already fixed in the LOCATION). It can be changed at any time with the GRASS GIS command g.region or with the GRASS plugin, even if you have defined a default GRASS region:


enter image description here


Example:


original region (in red):


enter image description here



after g.region:


enter image description here


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