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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83 views

ArcGIS Desktop equivalent to GRASS r.geomorphon algorithm?

I would like to know if in ArcGIS Desktop 10 there is some tool/algorithm which can be used to perform the same analysis that r.geomorphon does in GRASS 7.
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66 views

Merge different Landsat scenes in Grass GIS

I am new to Grass GIS, and I really need some help in solving this issue. I have 17 scenes from Landsat8 covering an area. I have created color infrared images of bands 5,4,3 and now I want to merge ...
3
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72 views

Underwater terrain modeling

My task is to model the surface of a lake bed, calculate volume of it and visualize it as 3D a surface. I have acquired depth measurements in a small lake using echosounder. The precision should be ...
3
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1answer
173 views

Shortest distance from polygon centroids to a line in QGIS

To get the distance of each polygon centroid from a line, I have tried the Distance to nearest hub algorithm from the Processing Toolbox. The distances I got from the algorithm did not seem correct, ...
3
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643 views

How do I use the GRASS command line tools within QGIS?

How do I use the GRASS command line tools within QGIS? I use the QRASS plugin to open the mapset, and then I open the GRASS tools window. I click on 'GRASS shell' under modules and it brings up a ...
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77 views

What defines a Class in the Heat map plugin?

What defines a Class in the Heat map plugin? As in: "Black holes like that are usually caused by raster values exceeding the range of the color ramp. Try adding another class with a higher associated ...
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1answer
252 views

How to prepare road network for routing in QGIS or GRASS

I have been working on a road network and I want to run shortest path algorithms on it. One problem is that some lines come very close to each other, but are not connected. Is there a way to connect ...
3
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2answers
161 views

Is r.cost equivalent to diffusion interpolation with barriers?

I want to perform interpolation using cost distances rather than euclidean distances similar to Greenberg et al. (2011). In that paper they use r.cost in GRASS to compute cost distances for each ...
3
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1answer
143 views

Issue with Sextante r.map calculator and modeler

I am trying to build a model with Sextante modeler and the r.mapcalculator algorithm but when I run the model I get the error message: ‘Could not load layer: ‘….’Check sextant log to look for errors ...
3
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1answer
126 views

Showing map in Grass Layer Manager/Map Display via Python

I've created some raster(tif) maps using Grass libraries in Python. I want to opem them automatically in Grass GIS Map Display or Layer Manager after creation. I don't want to use GUI for this. What ...
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115 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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132 views

Creating rasters?

I am doing my masters in archaeology, but have used GIS for some time now, however this is my first attempt at generating and using rasters. I appear to have been successful for some, but not so well ...
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2answers
179 views

How to make the layer 2 use the same vector categories from layer 1?

I'm having some doubts concerning the layer mechanism. Creating a new layer (ie a new connection between a vector and a DB table), I've imported a vector (rivers) through v.in.ogr, then I've cloned ...
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2answers
788 views

How to combine polygons in a vector with GRASS?

I need to combine polygons of similar geological classes which are stored in a vector file called geology. I was looking for somethiing like "union selected features" or similar. In the GRASS Book ...
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32 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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111 views

Pan sharpen Landsat 8 using Grass 7

I have followed this great tutorial on pan sharpening using Grass GIS 7 (I'm using beta 3). Everything in the tutorial seemed to have worked, but my final output is not as expected (pictured below). ...
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43 views

Option for 360 degree movie embedded in Open Source GIS software?

Is there any Open Source GIS software available to embed 360 degree movies with the map? For a COTS example, there is the Active Link Vision (ALV) extension for ArcGIS from IWANE.
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1answer
42 views

Why GRASS 7.0.0 can't create a table while importing shapefiles from QGIS?

I use GRASS7.0.0Beta1 and QGIS 2.4.0 on Windows8. With v.in.ogr, when I import a shapefile, I get the error message "Unable to create table". When I put the option of not importing the table, the ...
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72 views

IS it possible to run GRASS commands in the QGIS graphical modeler?

I have a geoalgorithm set up in the graphical modeler and everything runs except for the GRASS commands. It is really frustrating because when I execute these commands on their own they work just fine ...
3
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1answer
307 views

Solar irradiation calculation using r.sun

I am trying to compute the global solar irradiation for a region and the run times seem to be a bit too high. I have as inputs a Digital Surface Model with the buildings and a Digital Terrain Model ...
3
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2answers
144 views

GRASS v.rast.stats missing in sextante toolbox

I am new in the QGIS world and also with GRASS. I am really interested in using v.rast.stats as is doing exactly what I need. My problem is that I am not able to find it inside sextante in QGIS and I ...
3
votes
1answer
116 views

Wrong direction in r.watershed slope length calculation?

Or have I completely misunderstood something now? As a programmer I took it for granted that the row number would change if I traversed the map up and down in the program along the North-South axis ...
3
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2answers
257 views

Hand fit curve and then apply to time series of rasters, make a map. How?

Maybe a data management problem, not too sure, but likely a challenge which someone has dealt with before. I have a time series of rasters. I can summarise the information by taking averages of each ...
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3answers
475 views

Problem with v.in.ogr.qgis in QGIS

I received a shapefile containing data from a topographic survey of a farm. The file has a lot of lines containing elevation data. The person who made the survey did it with a GPS set up on a ATV. ...
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2answers
472 views

How to single out country data from a world data map?

Say that i have two "data sources"; A global map of average wind speeds, A shape file (or similar information) of all country borders in the world. How do i combine these two sources and extract ...
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705 views

How to identify line intersection in QGIS when I have more than 2 lines?

I am trying to identify where overlaps exist between multiple shapefiles. I would use the intersect tool, but it only allows me to intersect two layers. I have over one hundred individual line ...
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1answer
172 views

Combining Geological Grids and extruding between them?

I have a situation where I have 3 Geological grids, each showing a different horizon + the Seabed Grid. I need to extrude between these grids in order to make the 3D polygon for the geological ...
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2answers
1k views

saga & grass configuration in sextante (ubuntu)

I have some trouble in running saga and grass algorithms in sextante. When I double click it appears a pop-up saying: Missing dependency.This algorithm cannot be run :-( This algorithm requires SAGA ...
2
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1answer
1k views

GRASS Geoprocessing in Python Script

I´m trying to get some GRASS geoprocessig tools running in a python script outside GRASS. I´m able to import grass.script, but I´m not able to get the tools running yet. Does anybody know what I´m ...
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2answers
122 views

GRASS 6.4.0 and GRASS 6.4.SVN

What is the difference between GRASS 6.4.0 and GRASS 6.4.SVN? Thanks
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1answer
70 views

Fuzzy maps with QGIS/GRASSGIS

How to do fuzzy maps (FUZZY module in IDRISI) with QGIS/GRASSGIS?
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1answer
43 views

repeating steps in GRASS r.mapcalc

I simply cannot find out the following: I want to repeat a calculation in GRASS GIS several times. Is there a command for r.mapcalc to repeat a calculation x times (similar to this possibility in ...
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1answer
45 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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3answers
1k views

Viewshed / Line of Sight analysis- as a batch process?

I wish to carry out a line of site analysis similar to the subject in here (preferably within QGIS): Visual Impact Assessment in QGIS or GRASS Scenario: I have two points, A and B. Point A is a ...
2
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2answers
659 views

r.mapcalculator and python again

I've been trying to write a script creating binary maps: a=raw_input ("enter a threshold") b=float(a) grass.run_command('r.mapcalculator', formula="**'base_map'>=b**", outfile='map'+str(a), ...
2
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1answer
103 views

How to properly open an ASTER data?

Yesterday i downloaded an Aster L1B image from USGS's website. If i load it in QGIS, it doesn't get displayed properly(location wise). Even after i've enabled "On the fly" option, it's not reading the ...
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1answer
207 views

How to begin with tool development for GRASS gis or QGIS GRASS

I wanted to begin with customized tool development in Grass GIS or QGIS grass. How should i begin in to develop the tool. I search a lot in google search engine for begin with tool development in ...
2
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2answers
395 views

count features in polygon shapefile A that fall within each feature of polygon shapefile B

I have two polygon shapefiles, each of which contain multiple (possibly overlapping) polygons. Is there some way, using GRASS, to calculate the number of polygons belonging to shapefile A that fall ...
2
votes
1answer
744 views

How to handle multiple layers when importing a polygon shapefile into GRASS?

When I import a shapefile into GRASS, it seems to arrive as 3 layers. I.e. they appear in the qGIS toolbox browser as: myMap 0_polygon, myMap 1_polygon, myMap 2_polygon Is there a way to merge ...
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2answers
476 views

Layer Stacking in GRASS

Similar to layer stack feature in ERDAS what functionality is available in GRASS. I am aware of r.composite, but it can accept only 3 layers. To obtain a stack of more than 3 layers what can be done?
2
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1answer
90 views

Can the concentration of values in a raster map be known?

I have a generated raster map containing different flood levels. Is there a grass script to determine the percentage of values in a raster map? I'm thinking of using r.mapcalc to solve this, but I'm ...
2
votes
1answer
339 views

Command r.sunmask in GRASS

I have hypsometric model of relief, and I need to visualize shadows. I was suggested to use GRASS command r.sunmask, so I tried to set time values and run command, but it gives me an error "ERROR: ...
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2answers
150 views

Can the arrows produced by the d.rast.arrow GRASS script be queried or stored?

I have created a map with the flow directions using the d.rast.arrow. Can i query on the map to know where the direction of the arrows are? I am going to use the arrow directions in an algorithm. Or, ...
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2answers
84 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 ...
2
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1answer
47 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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1answer
64 views

Grass python shell can't find my data

I have a problem, the grass 7 python shell can't find my rasters. When I try to use the python shell to set the region I get "region not found". I can set the region in the grass shell (and other ...
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2answers
110 views

How to fix unreachable nodes in QGIS GRASS network?

I have created a network with the GRASS module v.net. But when I try to create the travelling salesman path with v.net.salesman, I get: Destination node 9383 is unreachable from node 9398 If I ...
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2answers
218 views

How to create isochrones from streets with distance values?

I have made isochrone lines using GRASS and QGIS, as shown. The lines show various distances to fire stations on a street network. Now I would like to turn these lines into polygons that look like ...
2
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2answers
216 views

How to increase resolution of 3D image in GRASS NVIZ

I am trying to make 3D visualization of terrain data and orthophoto using GRASS NVIZ via QGIS. I have been able to import both the DTM and the orthophoto in NVIZ window and successfully draped the ...
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2answers
59 views

How to produce maps with copyright imagery on it in GRASS?

I'm having some trouble with a GIS that I've got to produce. I work for a contractor and we'll have to produce maps to do the work for our client. The client has specified that if we print maps out ...