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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How to use r.mapcalculator to change values within a raster cost map to negative

I have created a cost map in r.cost module in GRASS (through QGIS). This is actually a distance map from a protected area and distance from protected area has been calculated in both directions. How I ...
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85 views

Trouble importing NumPy in GRASS. Architecture

I can't get GRASS to work on my system, and after doing some digging I think it is related to me using 64-bit python. I'm not really sure. I get this message... This module requires the ...
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1answer
136 views

GRASS i.landsat.toar returns empty raster

I am trying to use the GRASS module i.landsat.toar. Currently the files created are empty and it spits out: So it seems that it is not picking up something? The location is set to the extent of ...
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1answer
25 views

comparison of atmopsheric correction methods

I have noticed that dos methods for atmospheric corrections are in the section of radiometric correction (i.toar) on grass gis.Does that means that dos is a method doing radiometric and atmospheric ...
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285 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: ...
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1answer
126 views

How to recategorize features in GRASS by geometry, like the ArcGIS Sort tool?

The ArcGIS Sort tool creates a new feature class with features sorted by geometry. For example, it can number features IDs from north to south, etc. Is there a way to renumber the cat field in a GRASS ...
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1answer
366 views

How to make GRASS and SAGA tools capable to use in QGIS?

As my title, I installed Qgis, GRASS and GDAL by osGeo4w package, and as I finish the installation, I want to use GRASS tool, I face this problem: But I already installed GRASS and SAGA, how to make ...
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2k views

How to compute parameters for QGIS Affine transformation?

I have a vector floorplan (DXF) that I've added to a blank project in QGIS using the Dxf2Shp plugin. I've been reading tutorials and StackExchange threads, but I can't seem to find out how to ...
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28 views

Linearising aspect in GRASS GIS

After having produced aspect of surface in GRASS GIS and being aware that GRASS GIS calculates aspect counterclockwise from east, how could we transform aspect from being a circular variable (0-360 ...
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1answer
21 views

Mod function in GRASS GIS

What is the equal of ArcGIS Raster calculator "Mod" function (Finds the remainder of the first raster when divided by the second raster on a cell-by-cell basis.) in r. mapcalc in GRASS GIS?
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29 views

Execute GRASS command within qgis phython console

We try to calculate catchments with the r.water.outlet function from python console. To do so we use the following code: import processing rlayer = QgsRasterLayer("/my/path/DrainageDirection.tif", ...
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4answers
3k 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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46 views

Convert manual colored maps to vector

Is there a way to colorimetrically and automatically vectorize georeferenced rasters that came from manually colored, scanned maps? Currently we Print the topography maps 20k scale --> hand-coloring ...
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45 views

From Landsat spectral radiance (W/m2*sr*µm) to Global horizontal irradiance (W/m2) for mere mortals

We are working in a solar energy project to locate potential sites for solar panel farms. We are using the Landsat 7 panchromatic band to derive radiance with GRASS using i.landsat.toar (W/m2*sr*µm ...
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2answers
78 views

Use GRASS through R

I want to use GRASS GIS 7 through R 3.1.3 in kubuntu operational system. Could someone help me connect GRASS with R, and use GRASS commands through R (not the other way round!).
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1answer
47 views

topographic correction using GRASS 7.0 (**i.topo.corr**)

I would like to apply topographic correction using GRASS 7.0 (i.topo.corr). The imagery were already converted from DNs to Top-of-Atmosphere Radiances. When I apply the i.topo.corr command it runs ...
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39 views

Problem in running r.slope.aspect in GRASS

I am new to GRASS GIS, and have been trying to use the r.slope.aspect function to find out the slope, dx and dy rater map from an elevation map(512*512)[1]. But I am getting the following output: ...
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2answers
28 views

What logical function should i use to do a union of two raster files in GRASS?

The files are : DEM and roads. For the following i did euclid distance and then reclass. Now i need to know with what logical function to combine them elevation rank ...
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1answer
143 views

How to activate GRASS GIS 7 plugin in QGIS 2.8?

Apparently, my linux ubuntu setup of QGIS doesn't contain grass gis, although when I initially installed it last week I added grass gis to the command line. Anyway, I typed in once again and installed ...
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38 views

Problem in running r.sim.water

I am trying to run the r.sim.water in GRASS. I have calculated the partial derivatives dx and dy rater map using r.slope.aspect. I am using this elevation map [1] to get the time-series depth map. But ...
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15 views

GRASS watershed analysis add storm inlets

Try searching for this with no luck. I am using r.watershed to delineate flow directions, subwatersheds, etc. All good, except that storm drain inlets, culverts and subsurface drainage courses are ...
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42 views

Steiner tree problem: Optimal routes for Fibre planning on road network

I am trying to solve a large optimization problem where I have a set of nodes on a road network that need to be connected using fibre using the shortest possible amount of fibre. The problem is a ...
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1answer
46 views

How to add my own GRASS algorithms to Processing?

I need to use algorithm r.bioclimatic from GRASS in QGIS but I see that this algorithm don't exist in Processing Toolbox. A search a way of add this algorithm to Processing and in GRASS and Sextante ...
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3answers
40 views

GRASS convert raster to points

I have tried to convert a raster to points using this syntax: r.to.vect input=g_kelowna_merged@kelowna_mapset output=g_kelowna_points feature=point I have tried using the GRASS interface in QGIS and ...
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35 views

Why is QGIS 2.8.1 crashing when enabling Grass Plugin?

I am running Linux Mint 13 "Maya" (Ubuntu 12.04 Precise). I installed Grass via the software center. Than I installed Qgis 2.81 following this procedure: Add the lines for one of the repositories to ...
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77 views

How can I extract a smooth river network with QGIS & GRASS?

I´m working with Qgis 2.6.1 and GRASS. I have used the r.watershed module to create a flow accumulation map. With r.mapcalc I have extracted the river network, then i´m using r.thin to thin out to a ...
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23 views

Change GRASS module default parameter

I´m new to Qgis and GRASS. I need to change the default parameter skip of the module r.to.vect.lines, from its default value of 10 to 1.How can I do this? r.to.vect.lines [-v] input=name output=name ...
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10 views

Default horizonstep in r.sun

I am working on software suite to create some geoscience models on Digital Elevation Models. Part of the process is to calculate the Insolation Time and Global Irradiance using r.sun. We are running ...
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52 views

Simulate water runoff to get water height over each pixel of DEM

Here is my problem that I am trying to deal with. I have given a height map of around 512X512 resolution(It is Geo-referenced and I have the meta-data for this). And I have given that this area ...
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1answer
40 views

GRASS Zero-Crossing Edge Detection

I have a classification of vegetation communities across a landscape in a .tif format. I wanted to use the GRASS Zero-Crossing Edge Detection tool in QGIS to help define boundaries between my ...
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134 views

Can GRASS compute the line graph representation of an input graph?

I'm interested in computing a line graph for an input graph, preferably in GRASS since I'll be using other GRASS network analysis tools afterwards. I couldn't find any reference to line graphs in the ...
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71 views

How to create line segments between pairs of pixels in a raster?

I want to draw several lines between pixels (please see the image below) according to some criteria : First Criterion: The distance between 2 pixels is less than 2000m and greater than 500m ...
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1answer
13 views

Move Landsat 7 Image in Grass 7

I got 2 landsat 7 images from the same place but different date of adquisition, image A is well placed, but image B is shifted about 1500 meters east and 14700 meters north. I need to use both images ...
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67 views

How to reference a number variable in r.mapcalc within QGIS graphical modeler

I need to run the following formula in r.mapcalc: (xor(abs(A-B),abs(A-C))>120)*A I would like to however use a user defined number input variable instead of the 120. I already have this variable ...
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0answers
18 views

Second order rectification display problems

I'm using GRASS 7.0 to geo-rectify oblique images taken from a fixed altitude and using RTK-GPS data as a GCP (as a vector file) for the process. The survey area is very small and flat, so I'm not ...
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2answers
32 views

How to combine the content of several mapsets into one new mapset in GRASS.?

I have some mapsets and i want to assemble them into one new mapset and have everything into it. How do i do it?
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2answers
551 views

Is it possible to use GRASS GIS in Python stand alone scripts?

I am trying to find a least cost path script for Python. I came across r.drain from GRASS GIS. Is it possible to use GRASS GIS in a Python stand alone script? If so where can I download the bindings?
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1answer
25 views

Grass r.out.gdal, wrong values when importing to QGis

I have a problem with export/import functionalities between Grass and QGis. I create a raster file in Grass (with r.wind.sun, but that most likely does not matter) It has the following properties: ...
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1answer
34 views

Duplicated vertices in contour features of GRASS?

I use GRASS to produce contours from DEM (r.contours for SRTM rasters). They looks fine, but most of the line features occures to be duplicated; i.e. verticies duplicated. Here are pictures of output ...
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2answers
432 views

Creating contours for specific elevations

Input data: 1. an SRTM raster. 2. Point file of peaks. -Attributes contain ID, x, y, z and the elevation at which the peak is completely isolated from a neighboring peak. The output I want is a ...
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56 views

How to process a big number of raster outputs with r.series?

I am new to python and QGIS. I'm trying to take some simple operations (e.g. count, average) over a big number of raster maps from a python script. I'm using the "r.series" algorithm (from processing) ...
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18 views

Calculating Odd and Even side of road using PyQGIS and GRASS

I'm trying to programmatically and automatically assign odd and even sides of a road to number homes using QGIS and GRASS. I noticed this other post, which gives a solution using PostGIS and I have ...
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50 views

Least cost path analysis : a lot of sources and destinations

I'm working on a 15*10 km area, splatted in a 50*50 m cell grid. I want to compute the time needed to travel from a single starting point to each cell centroid, combining driving and walking time. I ...
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1answer
30 views

GRASS make local relief error

While using/trying to make a local relief in GRASS with the plugin r.local.relief i stumble across a error. ERROR: G_realloc: unable to allocate 15000000 bytes of memory at ...
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69 views

Preprocessing GeoEye-1 in GRASS iatcorr

I am trying to do a study on land use change using three high-res images of an area from three sources (Quickbird, GeoEye-1, WV-3). I have managed to calibrate the Quickbird data using QGIS raster ...
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4answers
2k views

Rubber sheeting in GRASS or QGIS

We are in the process of getting our property boundaries corrected and a side effect of this is that we need to move any assets that have been drawn relative to the property boundaries, so they are ...
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1answer
476 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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19 views

Why do GRASS' NC dataset and USGS' CONUS dataset coordinates disagree?

In the course of trying to figure out a specific data extraction task, I'm trying to understand the coordinate system used by GRASS. For a while, I'd been working with elevation data near Raleigh, NC, ...
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182 views

where to perform principal components analysis and tasseled cap transformation [closed]

I want to perform a principal components analysis (pca) and a tasseled cap transformation (tasscap) for a classification.Should i perform pca and tasscap on the original bands of my image or on the ...
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50 views

Time processing in GRASS?

I am computing NDVI for Landsat TM in grass 6.4.3 in raster map calculator, and time processing is many hours and finally tke message is "failed". trying to find a solution I discovered that it ...