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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Extract representative slope profiles from hillslope polygons

With the help of the Whitebox Geospatial Analysis Tools I was able to easily extract hillslopes from a river network in combination with a flow direction map. Now I would like to extract ...
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1answer
123 views

Python library for geometrical calculations using with GRASS GIS?

I have to do some geometrical calculations in 2D(point, lines, line segments and intersection points) in Python, and then use it in GRASS GIS. What is the best library to use for it? I'm trying with ...
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24 views

importing to tif

i am working on grass 6.4.4. i want to know the details of which GDAL version grass is using.i want to use r.in.gdal.exe which is giving "no dlls found in water fall model" error message.remaining ...
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1answer
109 views

Delination of half basins or hillslopes from a flow direction map or/and a stream network

I am using the GrassGIS r.stream.extract extension to delineate a stream network with the options 'mexp' (Montgomery exponent) and 'd8cut' (Use SFD above this threshold). It works perfect so far and ...
3
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1answer
534 views

Problems using r.reclass in QGIS: invalid reclass rule error?

I need to reclass some rasters, but i am having a couple of problems, i can´t generate a new raster with the reclassification using the r.reclass of GRASS. For the question here i´m using as example (...
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1answer
63 views

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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1answer
206 views

Using 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 ...
2
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1answer
469 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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35 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 ...
2
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2answers
412 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 k-...
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1answer
87 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: "...
2
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1answer
38 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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1answer
2k 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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0answers
552 views

Assessing Flood Hazard Risk Zones using DEM

My Question: What is the best effective way to quickly estimate flood hazard risk areas using DEM data? Ideally I am looking for guidance to move forward and perform this process over large areas (i.e....
5
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2answers
580 views

How to create a mosaic in QGIS with cutline and feathering for Landsat-8 imagery

1 - I have two scenes Landsat-8 RGB 6/5/4 and I need to mosaic them: 2- This is my cutline in polygon format that will smooth the overlapping area: 3 - So, I need to create a mosaic with ...
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1answer
224 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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0answers
110 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 ...
2
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1answer
54 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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0answers
30 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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1answer
103 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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1answer
165 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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1answer
77 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 ...
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1answer
86 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
82 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 v....
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1answer
165 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, ...
6
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1answer
225 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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2answers
423 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 http://glcfapp.glcf.umd.edu:8080/...
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1answer
56 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
146 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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121 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 surface"...
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2answers
80 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 ...
2
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1answer
439 views

Fuzzy maps with QGIS/GRASSGIS

How to do fuzzy maps (FUZZY module in IDRISI) with QGIS/GRASSGIS?
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50 views

GRASS GIS 7, Windows 8.1, Graphical Modeler, Export to Python

I need help. I´m trying to export my model made in Graphical Modeler in Grass GIS 7.0.0 beta3 to Python Script. The exported file contains only header.
4
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1answer
969 views

How to reproduce Smoothing from Generalizer Plugin in v.generalizer in Processing Toolbar using QGIS?

I´d like to reproduce the smoothing operations done with the Generalizer Plugin inside the v.generalizer Toolbox so I can use them on a polygon layer instead of only on a line layer. I tried ...
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1answer
228 views

How to eliminate polygon boundaries

I'm working in both ArcMap and Grass I have a problem with the boundaries or the edges of my vectors. The vectors are a result of object segmentation (called classification) in Grass Gis. In Grass, ...
3
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3answers
206 views

Find coordinates of given raster value

I would like to get the coordinates of a raster cell with a given value. I suppose many cells can take the same value, in which case several coordinates should be returned. In my first problem I'm ...
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1answer
253 views

GRASS scripting for producing multi-band raster

I am trying to loop the r.sun function within a Python script. Anyway, I seem not to understand how I can stack the raster maps each loop would produce into a single multi-band raster (preferably in ...
4
votes
1answer
303 views

Convert downloaded LiDAR info to DEM in GRASS

I have downloaded LiDAR information as a .asc file and a .tif file, and even though I have tried multiple methods to convert them to a dem I am having no luck. Grass GIS says there is an invalid ...
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1answer
233 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 ...
1
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1answer
447 views

Running GRASS functions in QGIS 2.4 from python console

I am using qgis 2.4 and i am looking for the "easiest" way to execute e.g. the r.in.gdal function from the python console in qgis. Specifically for r.in.gdal, I could not found this function in ...
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0answers
45 views

computing the volume of a cave

I did a cave survey and now I have a dxf file 3d. It's composed by 8 layers: polygonal points width contour width height contour height stations depth I would like to make a volume and change its ...
3
votes
2answers
339 views

QGIS GRASS shell commands not working in Yosemite

First time asking a question here. Running GRASS 6.4.3 within QGIS 2.4.0 on Mac OS 10.10 Yosemite. I'm trying to run v.net.iso within the GRASS shell, but the following error is returned every time: ...
0
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1answer
162 views

GRASS failed to import ESRI ASCII grid

I'm a new user of GRASS 6.4.3 and I wanted to import ESRI ASCII grid. Raster file was unzipped, and in r.in.arc window I specified name for output, storage type etc. After it has run, raster didn't ...
2
votes
1answer
108 views

Meaning of r.viewshed output numbers in QGIS?

I have completed a r.viewshed analysis of a point in GRASS7. I have imported the arising Geotiff into QGIS and when viewing the layer in the layer window (after expanding the +) I am presented with a ...
5
votes
1answer
1k views

Calculate flow path with QGIS

I am trying to replicate my erosion model in ArcGIS for Desktop in QGIS 2.4. I tried to calculate the upstream distance along the flow path for my agricultural field using QGIS. I did the equivalent ...
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0answers
36 views

bug in i.rgb.his

I found that the implementation of i.rgb.ihs in porcessing toolbox needs to be corrected. It is necessary to have admin permissions to correct the file i.rgb.his.txt locate in path_to_qgis/python/...
2
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1answer
246 views

Manual (or examples) of r.ros, r.spreadpath and r.spread in GRASS

you can report me references or applications for use of the following modules (GRASS): - r.ros, - r.spreadpath, - r.spread. Thanks so much.
2
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2answers
224 views

convert DTM txt file in geoTiff file

I have a DTM file, txt format, I would like to convert it into GeoTIFF, how can I do with the software grass? thanks ncols 1329 nrows 1152 xllcorner 1693884 yllcorner 5080341 ...
5
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0answers
123 views

What Does the Cell Value in a Composite Raster Mean?

When I make a composite raster in QGIS using the GRASS r.composite tool and then click on a certain cell I get these values in the blue/green/red/composite rasters: blue = 124 green = 124 red = 172 ...
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0answers
46 views

how to compile i.atcorr separately without compiling whole grass

i am working on grass. i need only i.atcorr module. should i compile whole grass 6.4.3 or any option is there for separate module compilation. I tried to compile entire gras6.4.3 on windows system but ...