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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Calculate raster mode with r.mode - problem with decimals

I am working with a raster file that represents the percentage of vinyards by commune (e.g., municipality) in a region in France. The statistics were calculated for each commune based on surveys from ...
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18 views

Calculate r.mode and r.univar with active MASK

This may be a very stupid question, but I am new in GRASS. I am calculating summary statistics with r.univar and the mode with r.mode. I have an active mask which differentiates agricultural from non ...
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2answers
192 views

GRASS tutorials, spec r.walk, r.cost

Recently got enamored with the idea of doing a time-based and an energy-based least cost path analysis. After doing some research, I see that GRASS is the best for executing time-based given the ...
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1answer
108 views

Use r.mapcalculator in Python console

I'm trying to use the r.mapcalculator algorithim in a python script, but I'm having problems in using the r.mapcalculator to tranform a raster layer with float values into integers. Using the ...
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27 views

execute binary from grass shell?

I am new to grass and could really use some help with my problem. I am using hydrologic modeling software, and it include a grass program that I need to run from the grass shell. My question is, how ...
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3k views

How to set all pixels with value <= 0 to “nodata” in DEM raster?

I have a DEM raster with pixel values between about 3000 and -0.0003. I need to set all pixel with a value of 0 and smaler (<=0) to "nodata" (for later raster calculations and to reduce the ...
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23 views

adding new sensor

i want to add new sensor in grass. i followed the link http://trac.osgeo.org/grass/browser/grass/trunk/imagery/i.atcorr/README and created the .csv for our sensor.but where should i incorporate this ...
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1k views

How to simplify a routable network?

I have a network graph that I need to simplify in the sense of reducing the number of edges. The idea would be to merge nodes that are located close together and remove the connecting short edges. ...
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184 views

How to extract percentage of land cover from a raster according to multiple shapefiles?

I have a raster map that represents land cover of a region, and different shapefiles (total 120) in the same region. I want to know the percentage of every land cover for each shapefile. For example, ...
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2answers
599 views

minimum distance from the shore (how to retrieve the “shore vertices”)

I am student of Statistics, this is my first time using GIS., I am sorry for the stupidity of the question but I browsed online and could not find a satisfactory answer. I have some spatial data in ...
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1answer
51 views

How to fix this “Sorry <1> is not a valid option” in GRASS-Ubuntu using r.water.outlet?

I am working with this .sh code (a while loop, extracted from: http://www.surfaces.co.il/) to create watersheds from drainage raster and outlet point of every watershed, but I obtain this error: ...
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1answer
595 views

What am I doing wrong with QGIS v.clean?

I thought I understood how the GRASS v.clean tool worked in QGIS (in 2.6.1 Brighton) but I keep getting unexpected results and errors with a polygon ShapeFile. I've run the QGIS TopologyChecker with ...
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171 views

Defining the boundary of a catchment area

I digitized contour lines from topographic maps and created a DEM. With the DEM, I estimated the boundary of a catchment area. Estimated positional accuracy of topographic maps is RMSE = 65 m, with a ...
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1answer
287 views

GRASS 7 - raster calculator “and”

I am struggling with one thing in the raster calculator in GRASS GIS 7: I want to create a raster_b from raster_a, with raster_a values between >=-0.15 and <=0.15. The raster containing values ...
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3answers
572 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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1answer
155 views

Which DOS method use to convert at-sensor radiance to at-surface values in GRASS (landsat data, i.landsat.toar modul)?

I am trying to calculate surface reflectance values from raw Landsat DN data downloaded from GLOVIS. I have imported Landsat data in GRASS 6 with header by i.landsat.import and reprojected the scene ...
2
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1answer
47 views

Appending map to another map using GRASS?

I'm trying to simply append a map to other map, without any sort of geometric operations as merge or intersects, just the original geometries with theirs attributes. This is what I already tried: # ...
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84 views

GRASS GIS G_malloc error

I am new to GIS. I downloaded GRASS and the sample data sets and am attempting to use the tutorial at: http://grasswiki.osgeo.org/wiki/Quick_wxGUI_tutorial. During the step, "Create a random ...
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1answer
132 views

grass - add on problem

I can't install the addon in grass 6.4.3 to my linux mint. i've already installed the SVN and than it says: GRASS 6.4.3 (fabian_idrisi):~ > g.extension r.fuzzy Fetching from GRASS-Addons SVN (be ...
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32 views

Changing tracks to vectors in a grid

This is a version of a question that I posted on the GRASS list, but I didn't get any suggestions there. I would like to overlay a grid (cell size about 500 m x 500m) over an animal track created from ...
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1answer
374 views

How to debug “Unable to load GDAL library” error 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 ...
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71 views

GRASS 6.4.4 vector command in crashes QGIS 2.4 (g.gisenv.exe has stopped working)

I am running Windows 8.1 64 bit, and have QGIS 2.4 and 2.6 installed. When I try to use a GRASS 6.4.4 vector command (specifically v.clean), I receive an error message in an endless loop, and the only ...
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1answer
87 views

GRASS GIS v.in.ply

I'm trying to import a .ply file from MeshLab 1.33 into GRASS GIS 7.0 using v.in.ply addon, but I get the error message: ERROR: List index must be integer, is uchar This appears to be referring to ...
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1answer
36 views

Cost Surface No sense Results. GRASS

I have some doubts with the generation of a cost surface with r.walk of GRASS. It's assumed that the resulting layer is measured in seconds, but when I try to convert seconds in days march (6h per ...
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25 views

Distance between each feature from and every feature to in GRASS

In GRASS, v.distance calculate the minimum distance from each point feature in the 'from'-layer to the nearest feature in the 'to'-layer. I should instead calculate the minimum distance from each ...
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73 views

Grass GIS “v.in.ogr”: How to prevent crossing lines from beeing split where they don't share a common node?

I want to import a road network into grass gis to run network analyses. I use "v.in.ogr" to import my road shapefile. The problem is that Grass GIS seems to split every crossing line no matter if they ...
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2answers
1k views

Is there a Focal Statistics (spatial analyst) tool in ArcGIS equivalent in QGIS?

I'm attempting to use QGIS v2.0.1 to accomplish the same tasks that I can do using ArcMap v10.1 and I'm running into some trouble finding equivalent tools. In ArcMap I am using the Focal Statistics ...
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40 views

6s parameters used in grass gis

I am working on grass gis 6.4.4 , i.atcorr module. There is no clear document for the parameters used for the calculation of 6s output parameters. I want to know about the parameters such as ti.sast, ...
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2answers
552 views

How to determine aerosol model value for i.atcorr in GRASS?

The i.atcorr module in GRASS requires aerosol model data to perform atmospheric correction using the 6S algorithm. It seems like I need a value from one of these parameters to continue: Estimate ...
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1answer
119 views

grass gis i.atcorr input should be reflectance or radiance

My question is what should be the input image in i.atcorr for grass 6.4.4 version? I tried giving both reflectance (DN) and radiance as input but values are coming properly. I read some where, it ...
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34 views

GRASS: How to remove several categories from a geometry?

I am totally new to GRASS (and have found it difficult to get into that way of thinking and its terminology). I use grass70 under Ubuntu 14.04. I have the following problem which I have tried to ...
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1answer
120 views

Qgis map composer shows a huge red cross

I can show this best by a picture: This cross also shows when I export it as raster or pdf. What is it and how can I get rid of it? I am using Qgis 2.4 and the map was done with the help of the ...
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12 views

How do we overcome the GRASS problem? [duplicate]

It appears that whichever version of QGIS I download when I open the program the same GRASS plugin window tells me "QGIS couldn't find your GRASS installation. Would you like to specify path (GISBASE) ...
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1answer
96 views

Adding items to DEM in QGIS

Working with QGIS and Grass I would like to produce a ZTV. I have the bare land DEM happily ready to go but would like to add buildings and woodland to the calculation. Can anyone please point me in ...
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66 views

Trouble installing v.class.mlpy add-on extension in Grass GIS

Background: I am trying to do OBIA analysis using the windows based Grass GUI. Not familiar with python coding process, environment. Problem: I've been trying to run the add-on extension but failed ...
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1answer
68 views

Problem installing r.hydrodem with g.extension in GRASS 7.0.0svn (r61585M) on mac OSX 10.10.1

I'm very interested in using the function r.hydrodem in GRASS, unfortunately, I'm running into some problems when trying to install this add-on in GRASS 7. I've tried installing some other add-ons ...
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1answer
514 views

SEXTANTE toolbox - GRASS error

I am trying to use the SEXTANTE module GRASS (and SAGA) for vector analysis but whatever function I use I always get the same error:"Could not load layer: G:/closest.shp Check the SEXTANTE log to look ...
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5answers
2k views

How to pansharpen LANDSAT 8 in GRASS?

Having used QGIS for quite some time for mapping, I was 'forced' to dig into GRASS as pansharpening is not directly executable in QGIS. After understanding more or less the structure, I did some ...
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1answer
51 views

Intermittent multi-threading in Grass 7?

I have a script with runs GRASS 7 r.li.* commands through R with spgrass6 on Ubuntu 14.04/64 bits. I ran the script and was amazed at the speed at which it was running. So, I looked at the system ...
6
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1answer
174 views

Cell declustering using open-source software

I want to perform cell declustering in a small point data set. I have 9 observation points and I want to find the size of the region of influence for an observation, and afterwards use that as ...
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4answers
2k views

How to find dead-ends in road network using ArcGIS for Desktop or GRASS?

I'm trying to remove all the dead-end roads in a road dataset (lines) that are less than 100m long. How do I identify roads that are dead-ends (no exit)? The 100m part is easy. I know how to use ...
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1answer
60 views

Compute nearest points to other points using GRASS

I have a layer of address points and a layer of polling stations. My task is to determine the three closest polling stations to each address on the street network. I think that the answer is in ...
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2answers
2k views

Is there a way to automate the preprocessing of LANDSAT data?

I'm currently enrolled in a remotesensing course, using LANDSAT data. Part of my course is about standardizing the scenes based on radiance values. I assume that because this is such a tedious task, ...
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1answer
51 views

can grass modules work separately

Grass is very useful tool for pre processing of imagery. I want to use the i.atcorr module separately. Will it be possible? I have compiled using .cpp files (AerosolConcentration.cpp, ...
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80 views

Only run r.neighbors if cell meets criteria

This is my first time using GRASS to work with Rasters, so please excuse my lack of knowledge on the subject. I want to run the GRASS r.neighbors function on cells that meet a specific criteria, ...
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2answers
190 views

Looking for guidance to create a hydrological map with QGIS and/or GRASS

I have QGIS and GRASS installed . Basically i need this program for making maps something like this: https://www.youtube.com/watch?v=5HuPX7JS7ZA I downloaded DEM from ...
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5answers
5k views

How to workaround large mosaic process which is failing?

I need to mosaic about 550Gb of tif imagery together and the software I have tried keeps failing. The area has been split into zones so that the smallest has approx 200 tiles. I have used the latest ...
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1answer
36 views

How to add grass64 to PATH variable

I recently installed GRASS 6.4 in a Unix environment. The application opens fine, but I would like to also be able to run the GUI from the command line. The tutorials says that the grass64 command ...
3
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1answer
88 views

To make a map of sinkholes on grass gis

I would like to make a map of sinkholes. I have a DTM ARC/INFO ASCII GRID of Asiago Plateau and and I'm using grass gis. Does anyone know what is the correct form in grass gis?
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2answers
40 views

changing mapset in cmd

can anyone suggest me for changing mapset from current location using command prompt.I have compiled the grass gis 6.4.4 and when ever i want to use the commands every time i am opening gui and ...