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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Two r.mapcalc calculations return a much bigger raster cell size than the input raster

I tried the following calculations with a GeoTiff sample, having a cell size of 25m: Calculating the togographic exposure (TOPEX) and estimating the mean topographic curvature Both, the resulting ...
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90 views

Area of a Cross Section GRASS GIS 7

I have a task I would like to solve with GRASS GIS 7, if somehow possible. I want to create a cross section from a landslide - and would like to calculate the area of that cross section/profile. Any ...
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33 views

Unable to set pg as default backend with osgeo4w GRASS

I am trying to set PostgreSQL as default backend for GRASS, but cannot manage to get it right. Working with GRASS 6.4.3 print g.run_command('db.connect', driver='pg', flags = 'c', ...
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157 views

Create network from shapefile without ArcGIS?

I want to perform shortest-path analysis on a network whose edges represent real-world roads and whose nodes are buildings or other locations. I have the shapefile for the area I'm interested in. ...
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74 views

Calculating vector statistics in GRASS

I have a points layer, each of points have an year attribute and I want to count how many points in each year. I use GRASS-GIS and its v.univar function: v.univar -e map=mod14_hmao column=year ...
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193 views

How to calculate peaks in a DEM

How could I extract all peaks from a DEM (large mountainous area)? Peak means something like: a pixel which is sourrounded by other pixels with smaler elevation numbers in a area arround the ...
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82 views

Empty raster returned after GRASS i.atcorr with Landsat8 data

I've searched at length on previous forums but no solution seems to work for me. I'm trying to run the i.atcorr module on GRASS (version 6.4.3 on a Macbook Pro, Mavericks OSX) with Landsat8 imagery. ...
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1answer
114 views

Python + Grass: No such file or directory: 'PERMANENT\\MYNAME' (solved)

I have an existing Python script that processes raster images with Gdal / Numpy. Now I want to extend the script with Grass. The python script is developed on Windows 7 with Eclipse/Pydev. The script ...
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80 views

How to use v.to.3d in GRASS GIS?

I am trying to use GRASS GIS for the first time. After quite a lot of trouble I managed to create a location and a new mapset, and my shapefile is now displayed in the window "GRASS GIS Map Display" ...
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83 views

How to simplify osm2po's routable graph?

I'm building a pgrouting routable network thanks to osm2po, the problem is that my network is too big. Indeed I want to create isochron and 1 node = 1 canvas circle, so I don't want too many nodes. I ...
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74 views

Debugging r.neighbors error in Processing

I'm having similar problems withs some GRASS algorithms in processing plugin. On the one hand i have installed Ubuntu 12.04 with Qgis 2.0.1. In this machine when I run r.neighbors algorithm don't ...
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1answer
53 views

Isolate the largest patch in a raster in GRASS?

I have a raster with a series of patches (contiguous areas with same value). How do I isolate the largest patch? I know I could run r.stats, look through the long list of calculated areas, figure out ...
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132 views

Processing area of interests within Grass GIS

I'm looking to process a region within a satellite image in Grass GIS. In ENVI I would create a region of interest (.roi) and then create a subset. Say, if I have co-ordinates for a rectangle within ...
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61 views

GRASS v.to.rast.attr returning null values

I am having a problem converting vectors to rasters in QGIS. As there is no tool where you can directly set the pixel size (instead of the height and width of the new file) in QGIS 1.8 (the version I ...
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41 views

Problem with GRASS in QGIS

I am trying to import a vectorlayer to GRASS from QGIS. I get an error and hope someone here can help. Been trying to fix it for hours, but come no closer to a solution..... This is the error I get: ...
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1answer
131 views

How to fix QGIS crashes when using GRASS toolbox?

I've installed QGIS 2.0.1 on Ubuntu 12.04. exactly as explained on qgis.org . Unfortunately QGIS crashes when trying to use any GRASS model (r.aspect as example): just opening QGIS, click on toolbox ...
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125 views

How to install GRASS in QGIS Dufour?

How do I install GRASS to run in QGIS 2.0.1? GRASS is not listed in the Plugin Manager and attempting to access it via the Processing Toolbox gives me the following error:
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99 views

Merging contour lines along tile boundaries

I am working with the CANVEC data set. The data in canvec is broken up in to mapsheets. eg. 116B04. I have data covering the entire province of the Yukon. I have merged all the data in to one ...
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32 views

Raster Interpolation of Different DEMs in GRASS

I am trying to generate a DEM for surface runoff modeling in GRASS. I have a DEM for the entire watershed at 1ft resolution and another for the small area within that watershed (a parking lot) I am ...
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103 views

Trouble with opening/using i.atcorr in GRASS

I'm relatively new to GRASS. I'm running version 6.4.3 on a Windows 7 machine. I'm trying to process Landsat 5 imagery from multiple states, so I was hoping to approximately follow the workflow here: ...
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1answer
182 views

How to pansharpen radiance/reflectance Landsat 8 in GRASS 7?

first at all, I have to say that I'm new GRASS user. I would like to make a pansharp in GRASS 7 with reflectance Landsat 8 bands. I have revised some related posts and blogs, and I didn't find out if ...
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58 views

Problem with r.drain in Dufour and 2.1

I am trying to perform to define the shortest route between two points using r. walk, r.cost and r. drain. I have successfully done it using grass under Lisboa standallone living in win7. When I try ...
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76 views

GRASS i.atcorr outputs unusual values

I have problems using the atmospheric correction module i.atcorr in GRASS 6.4.3RC3. I try to correct two Landsat ETM+ scenes, but the output for bands 4 and 7 has values that seem to be incorrect. ...
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85 views

Grass installation - MSVCR71.dll error while .Net installed

I have .Net 4.5.1 installed and resently installed GRASS 6.4.3. When I try to start the software I get the MSVCR71.dll error. The only solution suggested in the guide is to install the .Net ...
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155 views

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, ...
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134 views

How to join USDA SSURGO soil table data to features in QGIS?

I am trying to make a soil map using QGIS. The only problem is that I cannot join table data to features in QGIS. In ArcGIS for Desktop you just open the folder and then join the tabular table ...
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467 views

Import GRASS and SAGA modules to python script

I'm new at this. I am "building" a python plugin for qgis and I want to import modules from GRASS and SAGA but I don't understand how to do it. The plugin I want to import is Kriging interpolation ...
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1answer
88 views

Set Grass Region in Python grass.script

How can I set the Grass Region in Python without already having a map in the Mapset? Basically I am looking for the equivalent to this window Currently I am only able to extent an existing region, ...
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55 views

Error north coordinate not allowed using r.water.outlet in GRASS

When I am trying to delineate a basin from this code: r.water.outlet drainage=drainage1 basin=basin1 \ east=518675.070417019 north=911542.292643082 Coordinate system: UTM-cartesian xy (used by ...
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1answer
92 views

How to get the direction raster from r.walk or r.cost

I am trying to use r.cost and r.walk and r.drain to calculate the shortest path from an archaeological site to the nearest basalt source. I am using all this algorithms with the processing toolbox (I ...
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147 views

What are the advantages and disadvantages importing vs linking data in GRASS?

I'm fairly new to GRASS, and only recently discovered the r.external and v.external functions. I'm used to working with R and QGIS where all the data is "external". Typically I keep vector data in ...
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1answer
51 views

Re-sizing Raster file pixels

I have 2 JP2 aerial imagery files that are incorrectly sized. They are 100x larger than the other aerial images but correctly geo-referenced (starting x, y co-ordinates). I believe the issue is their ...
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85 views

Touch up tool for rasters?

I was wondering if it were at all possible to manipulate/massage rasters (eg Geotiff) using Qgis plugins or Grass?? By manipulate, I mean manually smooth off interpolation artefacts, blended surface ...
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2answers
539 views

install GRASS Addon in with QGIS

Win 7 QGIS 2.0 GRASS 6.4.3 Hi everybody, I want to install some GRASS-Addons to use them in QGIS. Therefore I run GRASS-Plugin in QGIS an open the GRASS-Shell type: g.extension GRASS opens then i ...
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56 views

how to work with netcdf data in Qgis 2?

Once it is displayed as a raster, how to see data of different time steps? eg. meteorology datamonthly mean and the likes... where to change the time step? how to calculate seasonal average, annual ...
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3answers
176 views

SRTM NASA hillshade grainy appearance

I'm trying to create a hillshade surface from SRTM files downloaded form Earth Explorer, but the appearance is not the expected. It has a grainy surface that I would like eliminate to have a ...
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2answers
112 views

Grass GIS 6.4.3, How to create a .PTS file

I'm trying to export a raster map in order to use it in the Flo-2d program. This program needs a .pts DTM file, do you know how I can create it? Alternatively, I can use a XYZ file looking like this ...
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1answer
537 views

How to get custom colormap onto 3D NVIZ in QGIS GRASS

I am trying to create a 3D version of my 2D raster using QGIS GRASS NVIZ. I have been following these steps: ...
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1answer
92 views

QGIS Grass Plugin fails with r.cost.vect

I tried the following in QGIS with the Grass Plugin: r.cost input=preCostSurface@albi start_points=OSMroads@albi output=cost0109 max_cost=0 And I get the following error: Dev note: Adapted sites ...
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1answer
396 views

Map Algebra - Grass GIS (r.mapcalc) merge two raster with NoData value

I have a slope raster and a road raster. The black pixels in the road raster are NoData values and the pink pixels have a value of 1. They don't cover exactly the same area. I want to create a new ...
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28 views

how to interpolate river bathymetry/heights in qgis/grass [duplicate]

Hi all and thanks for your help. I have a csv file containing a set of x,y,z points for river bottom depths. When trying to interpolate the data in scientific computing software (ie, matlab) I have a ...
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2answers
314 views

How to remove z & m coordinates from shapes with QGIS? (Or arcgis, grass, gdal, Python…)

I've recently received some parcel data in shapefile format that has z & m coordinates (all = 0.0). The WKT for a typical parcel looks like this: "MULTIPOLYGON (((2672464.560700002 ...
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189 views

how to make decent sense from scattered river depth measurements

I sampled river depth at scattered positions and I want to be able to make a map and GIS layers out of it. My problems are: As the river meanders the interpolation I do in scientific packages i,e. ...
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41 views

grass plugin in QGIS all of sudden not working as expected

The previous week I was able to use the grass scripts in the QGIS 2.0.1 Dufour toolbox, but today they do not seem to be working. I am not sure where to place a '-c' which was a solution to the same ...
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151 views

How can I create random concave polygons for test purposes?

In the context of generating random test data using QGIS (in a shapefile): I can generate random, continuous (adjacent) polygons by first creating n random points using ftools and then generating a ...
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122 views

filling up a depression to create new surface

A collegue here has a problem I cannot help with. She has the surface (as raster) of a landslide release area (from AFTER the slide) and wants to calculate the calculate the theoretical/approximate ...
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1answer
155 views

How to perform GRASS v.rast.stats via QGIS

I have been using qgis for the last few months. I got interested in using GRASS tools through QGIS. I wanted to compute zonal statistics for a raster surface for a given polygon layer. I loaded the ...
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1answer
114 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 ...
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2answers
107 views

Getting started with 'shell scripting loops' in GRASS

I'd like to work through the MODIS-Aqua example here. But typically the hardest bit is getting off the ground. What specifically does it mean by 'shell scripting'? is it referring to the command ...
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1answer
126 views

How to compare accuracy of two DEM using GRASS

How do I compare accuracy of two DEM data (lidar and srtm) (possibly through rmse) using GRASS GIS? thanks