[GIS] r.watershed analysis error from raster map being in different zone and unable to be opened

grassqgis-plugins

I tried running my DEM (geotiff) file through the r.watershed program by the GRASS GIS plugin of QGIS. I believe the error message results from a raster map in the different zone than the current region but I set my GRASS GIS mapset in WGS84-Zone 16N coordinate system where it ought to be. Thank you in advance.

Here is the error message I get:

r.watershed elevation=dem2@Tejeras threshold=30 accumulation=dem2_accum drainage=dem2_drain stream=dem2_stream basin=dem2_basin

SECTION 1a (of 5): Initiating Memory.

Raster map is in different zone (16) than current region (0)

Unable to open raster map 

unable to open elevation map layer

Subprocess failed with exit code 1

category information for [dem2_accum] in [Tejeras] missing or invalid

category information for [dem2_drain] in [Tejeras] missing or invalid

category information for [dem2_basin] in [Tejeras] missing or invalid

category information for [dem2_stream] in [Tejeras] missing or invalid
Finished with error

Best Answer

I answered my own question: Go into Grass GIS interface and look for g.region (should be under Settings->Region->Set Region. Since my raster file (geotiff) was already set in WGS84-UTM 16N Zone I just needed to use the second option (labled as '[multiple] Set Region to match this Raster Map') and select my raster file (which happens to be a DEM). Then click Run and your done.

Related Solutions

QGIS – Defining GRASS Region in QGIS

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

[GIS] G_malloc error while running r.watershed in GRASS 7.0.4

You are simply running out of memory while using the in-memory-mode of r.watershed. Proof: your current computational region (g.region -p) output is

> 57567 * 53957
[1] 3106142619

which exceeds, according to the r.watershed manual page, the in-memory-mode limit of:

> 2^31
[1] 2147483648

Solution: switch to disk swap mode ("seg" mode, see the r.watershed manual page) by setting the -m flag. Be sure to have enough free disk space then for the needed swapping.

Best Answer

Related Solutions

QGIS – Defining GRASS Region in QGIS

[GIS] G_malloc error while running r.watershed in GRASS 7.0.4

Related Question