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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4
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1answer
33 views

How to calculate “water accumulated in each cell” using QGis?

I create channel network and catchment area from a DEM with SAGA GIS. I know that flow is starting from a cell to an other cell. Firstly, a cell is filled with water and then it is starting to flow ...
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23 views

Hydropower Calculation

I have assigned the elevation and the volume flow to each point at a river (with v.to.db and v.what.rast). Now I want to calculate the Elevation difference between each pair of points and then ...
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28 views

How to decide when flood started depending on the rainfall data?

I created a raster with the point values (mm) of rainfall data by interpolation in the raster menu. So I have a raster rainfall data and a DEM. With this rainfall data and a DEM corresponding to ...
1
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1answer
22 views

Calculate River Runoff Volume (Q) with GRASS

I want to calculate Hydropower between points at a River. I already created a Rivernetwork and the Accumulationmap (without weighting) with r.watershed. My next Step was to set equivalent points along ...
0
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1answer
19 views

How can I fill the category field in a raster using GRASS

I have a tiff file with land use data. The land use class in in the value field, but the label field is empty. Now I want to find out which is the area covered by each land use class, but GRASS does ...
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22 views

setting null values to 0 Landsat 8 Grass 7.1

I am working with Landsat8 images and need to run the albedo function in Grass 7.1.svn. In order to do this, I need to set the null values to 0 to eliminate the black border around the images. This ...
0
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0answers
13 views

automatic extraction of dtm using grass gis

i have generated dsm using erdas lps tool which is in img format. i want to import this file in grass gis and extract dtm. can you please tell me how to input the data , in which format it should be, ...
0
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1answer
33 views

Isochrone driving/public transport map : Grass or postgis?

I have to do Isochrone driving / public transport map. It would seem that the two better open-source solutions are grass and postgis. Could you tell me which one is the better? the easier to ...
1
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0answers
17 views

What is the background processing of rainfall thresholding?

I want to create a flood map using Quantum GIS. First of all I create catchment area (flow accumulation). Then, I delineate a Channel Network by applying a threshold to flow accumulation. So I want to ...
0
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1answer
12 views

tutorial for deriving solar insolation estimates from high resolution Digital surface model

I want to estimate solar insolation using grass gis. I have a high resolution DSM generated from Large Format Digital camera.Being a novice in this field i Would like to have a tutorial and steps to ...
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9 views

How to visualize insolation rasters over color orthophoto in grass

I have generated insolation time raster map using DSM, slope, aspect for day 100 and time 10.95 hrs using r.sun module in grass. The output insolation raster map (color table) i want to overlay on ...
1
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1answer
23 views

How to do a looping for importing and interpolating a lot of LIDAR files?

I'm quite new to Grass Gis and I'm trying to make DEM (digital elevation model) for modelling flooding. I have 170 *.xyz files, which need to be scanned for extents (r.in.xyz -s input=...\filename.xyz ...
0
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1answer
25 views

How to change the Map Units in Grass?

because v.segment measures all offsets in map units, i have to change it. (I want to put all of 50 meters a point) So I checked g.proj -p: -PROJ_UNITS------------------------------------------------ ...
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0answers
22 views

problem with running raster calculator in grassgis

When I was trying to do NDVI with grassGIS I faced a problem. I cannot run the raster calculation. When I looked to the command console I see that (Sat Feb 21 12:41:58 2015) r.mapcalc ddes = ( ...
0
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0answers
16 views

Color polygon centroid according to attribute value in GRASS

I have many polygons in GRASS and want to color them according to their T-value. I can use v.colors and define a color table. That works fine when I plot the areas of the polygons. However, I would ...
1
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1answer
28 views

GRASS 7.1 (dev.) i.landsat.toar error

I am working with Landsat 8 image acquired in 2014. I am trying to convert the raw image (DN) to Top Of Atmosphere Reflectance/Radiance (i.landsat.toar) in Grass 7.1 (still under development). The ...
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0answers
30 views

Horton Stream Order as Category for r.fixed.segmetpoints with GRASS?

I'm working with Grass GIS. I want to use v.segment to set discrete, equidistant Streampoints (starting from each mouth). Since the water network is too large, it is impossible to define the rules ...
1
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1answer
20 views

How to change GRASS language within QGIS?

I use GRASS plugin inside QGIS on Japanese version of windows 7 x64. As I start GRASS tools, all the content show in English but when I try to execute a tool, tools option dispalys in Japanese ...
0
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2answers
25 views

Export GRASS raster as GeoTiff : nodata values exported as -nan (what happens in R?)

I am using the package raster to work with GeoTiff raster files which I expoerted from GRASS using r.out.gdal. GRASS assigned the value -nan to some raster files (type FLOAT32) for missing values. ...
1
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1answer
31 views

Export of group = multiband raster to another format not works in GRASS

I am really new in GRASS and my question is really basic but I dont realize where I am wrong. I have a set of single layers in my PERMANENT from some Landsat images (1 landsat = 7 one layer ...
0
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1answer
15 views

Overlaying of raster in GRASS for visualization?

I have generated insolation time rasters map in grass using r.sun module. How to overlay insolation time rasters over DSM depicting the color table for visualization?
2
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1answer
42 views

Can QGIS or GRASS convert layer files to shapefiles?

Should I be downloading QGIS or GRASS? I want the program with the most features. Most importantly, I have a lot of .lyr files. Can either of these softwares convert to shp and if so, how can I do ...
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0answers
6 views

GRASS GIS: Network analysis doesn't work correctly

I got a problem with the Network Analysis function v.net.iso in GRASS. I tried it so many times but the function doesn't work correctly. I tried to calculate isolines via the function v.net.iso, based ...
0
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3answers
58 views

Discrete Waterpoints with Grass

I've been working with Grass GIS for about two months. I have to develop a method for the identification of target regions of small hydropower plants. Boundary conditions are a predetermined minimum ...
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0answers
17 views

Raster Mosaicking GRASS Issue

I have a project where I have to download DEMs from USGS and mosaic them. So I downloaded them from EarthExplorer and imported them into GRASS. When I start the GUI version of r.patch using the ...
2
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1answer
71 views

GRASS GIS 7 in QGIS 2.6.1, Windows 7 64bit - Missing dependency

I am using QGIS Brighton 2.6.1. Today I have installed Grass GIS 7.0.0 RC2 to try its topology functions in QGIS. I have activated the provider, set the paths, but everytime I try to use any Grass ...
5
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0answers
56 views

Is it possible to generate a boustrophedon pattern which fill a vector Region with GRASS?

Every thing is in the title... I have a vector region in GRASS. And I would like to generate a vector (a polyline) beeing the bostrophedon pattern which fill this region. In the picture bellow, I ...
0
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0answers
12 views

r.watershed outputs different depending on use of console and toolbox

I am returned two different outputs despite same input parameters from r.watershed depending on whether I run it from the console or from the GRASS toolbox. The threshold for both is 5000. They both ...
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0answers
9 views

r.water.outlet returning blank raster

I am trying to delineate a watershed using r.water.outlet. I have created a flow direction raster using r.watershed (threshold = 50) (cell size is 300m). I use this flow direction raster in ...
0
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1answer
26 views

Draw lake isobaths having depth points and coast line

For some lakes, I have a line shapefile representing the coast line and some points with many information, among which depth (in meters). Is there a way to draw an isobath linking every point with the ...
1
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2answers
27 views

many add-on don't works GRASS 6.4.3

I use GRASS 6.4.3 on windows 7 64 bit. GRASS has been installed with QGIS 2.6.1. I have added r.stream.* adds-on by SVN. For each add-on, messages of installation were : OK. But when I try the ...
0
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1answer
27 views

Raster import from GRASS to R - handling nan/NA

I have several doubts, so I will try to be as clear as possible... thanks for your understanding. I am generating a regression model using several environmental covariates. Before importing the GIS ...
0
votes
1answer
45 views

Grass 7 on Ubuntu 14.04. Can't start Grass

I attempted to install GRASS GIS 7 on ubuntu 14.04 using these instructions. When I call grass70 from the command line I get a welcome message and a prompt to continue. I then get two error messages: ...
1
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2answers
45 views

r.in.xyz doesn't work in GRASS

I have these LIDAR data *.xyz files (1st col x, 2nd col y, 3rd col z) 485000.16 6508997.48 1.84 485001.27 6508998.92 1.86 485001.02 6508996.68 1.85 485000.77 6508994.45 1.79 485000.52 6508992.19 1.79 ...
1
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0answers
21 views

Displaying a Digitial Elevation Model using GRASS GIS draped by an RGB Raster

I have the following: Digital Elevation Model from SRTM LANDSAT Imagery from the same area I wish to display the DEM draped with the raster band combination (3,2,1) using GRASS GIS. My ...
1
vote
1answer
26 views

Unable to find a specific GRASS add-on in QGIS

I would like to use the r.xtent add-on made for GRASS GIS (http://svn.osgeo.org/grass/grass-addons/grass6/raster/r.xtent/description.html) in QGIS using the GRASS plugin, but I can't seem to find it. ...
1
vote
1answer
28 views

i.landsat.toar doesn't Work With Band 6 of Landsat 7 in Grass 7

I'm facing an issue when running i.landsat.toar with a Landsat 7 image, here's the list of files: LE70010752014040CUB00_B1 LE70010752014040CUB00_B2 LE70010752014040CUB00_B3 LE70010752014040CUB00_B4 ...
0
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1answer
40 views

Calculate shortest path not on land but over sea

I wonder if someone can give me some advice on how to calculate the shortest path between two points, not over land but over sea. I know that I will have to take in to account the magnitude of sea ...
3
votes
1answer
63 views

It is possible to verify landsat reflectance values?

My question is really wide today, as I am still beginner in Remote sensing. I´ve asked a GRASS programmer to prepare for me Landsat reflectance values from raw DN values (1 scene per year from 1987 to ...
2
votes
0answers
36 views

3D interpolating

Our final year project domain is soil contamination modeling. We collected soil samples at the depths of 0.3 cm ,0.5cm , 1cm , 1.5 cm in about 25 locations. We considered 8 contaminants- p h, sodium, ...
1
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0answers
40 views

Error when using r.watershed

When i am calculating LS Factor using Grass r.watershed the error "Raster map or group not found" (image below) keeps turning on. I don´t understand why this error happens if i am using a elevation ...
1
vote
1answer
26 views

Difference between FCELL, DCELL and CELL in GRASS GIS?

Can anyone clarify for me please the options in the "precision" parameter when calculating slope, aspect and curvature in GRASS GIS. What is the difference between FCELL, DCELL and CELL?
1
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0answers
45 views

QGIS and GRASS r.fill.dir processing times

I am new to the open source software and have performed analysis in ArcGIS in the past. I am learning as I go on this processes for OS. I am trying to calculate stream order (strahler) on a 1 gig ...
1
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1answer
100 views

QGIS 2.6.1 Brighton/ Grass pluggin r.stream.xxxx

I just updated my OSGeo4W and now have QGIS 2.6.1 and GRASS 6.4.4 and am trying to get strahler stream order. I am figuring out GRASS 6.4.4 GUI by itself but GRASS is easier withing QGIS, however, I ...
2
votes
1answer
62 views

GRASS plugin absent from QGIS 2.6 OSGeo4W install

I've just installed QGIS 2.6 Brighton using the OSGeo4W installation. The GRASS toolbox plugin has not, however installed as it had been with previous versions. Before, I was able to access the GRASS ...
0
votes
1answer
27 views

to remove location of grass

i wan to delete the Location of a data set in grass gis 6.4.4 using grass command. For customizing grass for our data set, i need to load different location and mapsets of different regions of ...
2
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0answers
81 views

Import vtk file in grass gis

last summer I made the relief of a cave, and at this time I returned with Therion software. This survey is in 3d and I can save it in the formats .Lox, .3d, vtk. I would like to import it in grass or ...
3
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0answers
61 views

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 ...
2
votes
1answer
53 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 ...
0
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0answers
12 views

r.massmov GRASS Addon execution error

I'm a rookie Grass7.0 user, and I am having a problem in executing the r.massmov addon. After installing r.massmov through the graphical user interface (Menu - Settings - Addons Extension - Install), ...