GRASS GIS (Geographic Resources Analysis Support System) is a free, open source geographical information system (GIS) capable of handling raster, topological vector, image processing, and graphic data.

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Tutorial on how to model flooding using data from gauging stations along rivers in QGIS?

Can someone please direct me to a tutorial where I can learn more about how to model flooding using data from gauging stations along rivers using QGIS?
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7 views

GRASS: v.drape, v.split and v.to.db on spearfish sample data

I am new to GRASS and started training on the spearfish sample data set in GRASS 6.4.3. I selected a bicycle tour and transformed it into a polyline. My next goal is to read out the slope and ...
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2answers
112 views

How to import R-generated .gri/.grd raster files in grass?

I received data in .grd + .gri format, where the first one is a small text file and the second one (having the same name) is a binary file. I am unable to open them in grass/qgis. Any hint ? Missing ...
3
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2answers
61 views

LiDAR data density, returns per square meter

How can I compute a raster showing the number of return points per square meter using SAGA GIS or other open source software? My goal is to obtain a mask which would show me the places (cells) ...
1
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1answer
33 views

What's the difference between Processing GRASS and the GRASS toolbar?

Preparing a QGIS-course for my colleagues I stumbled over the following question: What is the difference between the GRASS commands in the processing toolbar and the GRASS Tools, that you access via ...
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1answer
44 views

how to mosaic rasters in grass gis?

I am new user of GRASS GIS. I need to know how can i mosaic different satellite imageries using GRASS GUI? I was trying to use i.image.mosaic, but could not succeed. I have been looking for online ...
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1answer
84 views

Why can't I load more than 12 elevation files into NVIZ?

I have a large set of rasters in a GRASS mapset, which I would like to use as frames in an animation, visualizing the raster data as elevation. NVIZ is an obvious tool for this, but I'm having trouble ...
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0answers
13 views

Problem with Command Console (GRASS GIS 7.0,0 beta2 on Windows 8.1)

I have a problem with Command Console. When I do for example, File-> Map display-> Add raster-> elevation, it works. But when I write into Command Console d.rast map=elevation@PERMANENT, it ...
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15 views

Execute Spyder within Grass GIS

I'm using GRASS Gis with a small Python script. Is there a way (for windows users) to use the sypder ide within grass? I looked at http://grasswiki.osgeo.org/wiki/Tools_for_Python_programming but ...
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0answers
124 views

Can't launch GRASS GIS 6.4.3 GUI on windows 8.1

As title, I downloaded GRASS GIS from this website: GRASS GIS - Home, and I choose winGRASS 6.4.3 standalone installer to download. After I installed, I click on its icon: I can't launch it even ...
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2answers
28 views

r.topidx error: required parameter output not set

I'm calling GRASS r.topidx from QGIS 2.2.0. I can get other tools to work on the DTM, for example r.watershed. But r.topidx I get the Oops message: Oooops! The following output layers could not be ...
1
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1answer
15 views

Is my code for changing the resolution correct?

I have a raster files of daily minimum temperature (tmin) for the period 1962-2011 at a resolution of 1.125. I need to convert each single day raster file into 0.5 using inverse distance ...
3
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2answers
1k views

How to reclassify a float raster?

I have three rasters which represent distance (in metres) from certain things (bus stops, parks, libraries). I would like to reclassify these rasters so that they get integer values based on the ...
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0answers
14 views

GRASS and r.viewshed

I'm trying to run the r.viewshed command using co-ordinates held in a .csv file I imported using v.in.ascii. It has over 200 rows and I'm looking to run viewsheds from each line, without doing it ...
1
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1answer
36 views

Compute number of days with snow

I have a project and I want to map the effective number of days with snow cover for a year in some mountain area. Until now, I have processed the MOD10A2 (8 days snow cover) product derived from MODIS ...
0
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1answer
26 views

QGIS – Raster Calculator: Using flat (no data) areas of an aspect-raster in the raster calculator

I´m playing around with the Raster tools, following more or less the qgis-tutorial but using my own data. When I calculate the aspect of a DEM, flat areas are (logically) left without data. However, ...
2
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4answers
579 views

Unable to load GRASS plugin

I upgraded from QGIS 1.7.0 to 1.8.0, including updating GRASS to version 6.4.3. Since then, GRASS isn't any longer listed in the Fetch Python plugins. I uninstalled and re-installed the whole package ...
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1answer
30 views

How to check the resolution of converted raster file

I have a raster file whose resolution I need to change to 0.5. I do this using this: g.region rast=my_raster res=0.5 After running this command, how do I verify whether the resolution has actually ...
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1answer
24 views

Why is the raster information No Data value set to -1.#IND?

I have a couple rasters that have been atmospherically corrected using the "landsat.toar" tool in Grass. When these rasters are output and I open up their properties in ArcCatalog, the NoData Value ...
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0answers
13 views

v.clean in QGIS Python console

I have tried to use v.clean and v.clean.advanced (by GRASS GIS) within a script in QGIS, and was not able. I followed instructions here:, but was not able to do so. I got message: "No module named ...
2
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2answers
157 views

Issue while running grass from subprocess

I have a map based web application using geodjango. I needed to display the crime hotspots within a selected polygon area. I found that v.kernel is very good for generating heatmaps/hotspots. So in my ...
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27 views

Does somebody has a Python script for a Multiple Flow Algorithm?

I´m looking for for a python script for a multiple flow algorithm assigning flow to all lower cells from one central cell. This algorithm is part of the r.terraflow and would need it to start at a ...
2
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0answers
45 views

Shortest distance from polygon centroids to a line in QGIS

To get the distance of each polygon centroid from a line, I have tried the Distance to nearest hub algorithm from the Processing Toolbox. The distances I got from the algorithm did not seem correct, ...
2
votes
1answer
206 views

Raster map in different zone () than region ()

I am new to QGIS (just installed QGIS 2.0.1) and am having problems running any spatial analysis tools. I followed the instructions on how to call GRASS tools into QGIS, but when I try to run the ...
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2answers
20 views

Adjacency matrix in GRASS

I have a line shapefile that I use as network. I connect a set of point to it using "v.net operation connect" command. . My questions are: (i) how can I get the list of neighbors for each ...
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2answers
220 views

Error from ps.map in GRASS. How to fix?

I'm trying to learn how to use ps.map in GRASS. I thought that running it in interactive mode from the command line would be a good place to start, but I'm getting the following error: > ps.map ...
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1answer
23 views

Empty signature file after i.gensig in Grass (SOLVED)

I'm trying to make a supervised classification in Grass 6.4.3 under Linuxmint 16. After digitizing the training areas, I transformed them from vector to raster. Then I've done the following: just in ...
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0answers
17 views

GRASS r.out.mat memory issues

we have built a model with pythn/GRASS that calls the r.out.mat module. The area is quite large 25,000x25,000 cells. The machine we are running it on is Windows 7 machine with 16GB of RAM. After a ...
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1answer
55 views

What is the typical v.surf.xxx exicution time?

What is the typical v.surf.xxx exicution time? I am trying to run v.surf.bspline on a set of ~1600 points. It has bee running for about an hour now and is stuck at spot indicated in the image. I ...
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1answer
29 views

NVIS module not found in QGis

When I try to use the nvis module in Grass, QGis, pops-up a warning window saying "Module nviz not found". how can I solve this issue and use the nviz?
3
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1answer
96 views

95 percent volume contour

I generated, from point data, a kernel density map using GRASS, and I would like to identify the 95% volume contour in it. Is it possible in GRASS? Thank you
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1answer
30 views

How to modify existing grass gis tools and run them in QGIS?

I would like to take an existing tool of the grass tool box and modify the code to the specific needs of my task. As I´m struggling to start some kick-off would be great. How to access code? What do I ...
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0answers
18 views

r.composite gives blank image output in GRASS GIS

While running r.composite in GRASSGIS GUI command the image formed looks absolutely blank. The data I used is listed here below. IRS-LISS III Multispectral coverages. (i.e. band 2, 3 and 4 for Blue, ...
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1answer
271 views

r.surf.contour in QGIS 2.0

I have a problem with r.surf.contour. I create a DTM with v.to.rast.attribute and then use the r.surf.contour and it works fine in QGIS 1.9 but with QGIS 2.0 doesn't work. I have a contour shapefile ...
0
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1answer
136 views

Problem opening GRASS GUI: libgeos-3.3.6.so: cannot open shared object file:

I have been using GRASS to process some Landsat imagery but very recently, and as far as I am aware - after having done nothing different or changing the settings, I am trying to use GRASS and on ...
2
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1answer
147 views

Installing QGIS 2.0 with the newest gdal and geos libraries

I want to install QGIS 2.0 on Ubuntu 12.04 LTS. I followed these steps until the final installation command. Before I compiled gdal 1.10, geos 3.4.2 and grass 6.4.3 on my own. In the synaptic ...
0
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1answer
18 views

Help me to understand how i.fusion.brovey works in Grass 6.4.3

I'm using Grass 6.4.3 in Linuxmint 16. I don't have a very big problem but I'm trying to understand what is Grass doing, if I'm applying the process correctly and if there is something wrong with my ...
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2answers
97 views

“Missing dependency.This algorithm cannot be run :-(” QGIS + GRASS Windows 7

Windows 7, OsGeo4W pack installed including QGis 2.4.0 and GRASS. I Qgis when i try to execute a GRASS geoprocessing algorithm i get this popup: "Missing dependency.This algorithm cannot be run :-( ...
3
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2answers
217 views

How to split lines into equal segments with QGIS?

I'm attempting to split a curved (wiggle) line into equal length segments. Have used Grass's v.split which works to a degree but does not provide the output I'm after. v.split will extract segmented ...
0
votes
1answer
109 views

Removing Image Stripes / Scan Line errors

I have some seabed bathymetry data derived from seismic reflection profiles in a 2.5D dataset (closely spaced lines). The data was gridded by another worker in SMT Kingdom suite; I'm not familiar ...
2
votes
2answers
301 views

How do I reproject one raster to match another's in GRASS

I have two raster layers, A and B, which have information about the same location but have different projections and datums. How can I reproject layer A to match the projection and datum of layer B? ...
3
votes
2answers
2k views

How to generate a DEM from a contour Shapefile?

I want to create a DEM from depth contours (shapefile) in QGIS. I've been trying to work out how to do this based on this previous question, notably from this link from that page, however I'm stuck, ...
1
vote
1answer
44 views

GRASS GIS: auto-completion fails in commande line

I'm running GRASS GIS 6.4.3. on Win 7, SP1, 64 bit. The path to my grass-DB is: D:\grassdb Within the GRASS GIS Commande Line, if I press the tab-key to auto-complete only folders, files and ...
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0answers
17 views

qgis: module crashed or killed

using Grass 6.4.3. via Qgis 2.2.0 Valmiera (standard installation package): Why would Grass modules suddenly produce a "module cashed or killed" error. specifically in relation to r.surf.idw2 and ...
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1answer
361 views

Create a 3D surface from xyz csv using GRASS

Apologies if this is a repeat question guys. I am trying to create a 3D bathymetry surface from xyz data. There is approximately 300,000 points with lat, long and z (depth data). The data is sonar ...
0
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1answer
22 views

GRASS raster map types: UInt16 and Float64

i am in the processing of using r.out.gdal to export DEMs from GRASS into QGIS this is the output of the first try: using UInt16 as the data type. r.out.gdal input=DEM0maslTopog@UTM_35S ...
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0answers
21 views

GRASS workflow for volume calculation

i am attempting a volume calculation using the route of 2 dems (upper and lower) and trying to subtract the difference. workflow as follows: A. rasterise vector contours (v.to.rast.attr) B. create ...
0
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1answer
18 views

QGIS GRASS vector simplification creates duplicate data rows

When simplifying polygons in QGIS (2.2.0) with the GRASS v.generalize tool the resulting layer duplicates some data rows many times. A shapefile of 657 zones/data rows: .. is simplified to one ...
3
votes
2answers
146 views

Is r.cost equivalent to diffusion interpolation with barriers?

I want to perform interpolation using cost distances rather than euclidean distances similar to Greenberg et al. (2011). In that paper they use r.cost in GRASS to compute cost distances for each ...
2
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0answers
49 views

Background (sky/terrain) of a viewshed

Is it possible to determine whether a point feature of a particular height would be backed by sky or by terrain? I've done the viewsheed analysis of a wind turbine. Now I would like to make a raster ...