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 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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494 views

Cleaning shapefiles with islands in GRASS GIS

This may be very simple, but I'm new to GRASS GIS. I have a large shapefile containing global species ranges, which needs topological cleaning. I imported this into GRASS GIS 6.4.3 using v.in.ogr (a ...
3
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2answers
489 views

Creating square buffer in qgis

How can I create a buffer with square ends along a line segment in qgis? I've buffered lines using v.buffer in the GRASS plugin, but the -c option for square ends is not exposed in that interface. ...
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3answers
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 ...
4
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1answer
369 views

Topology problems with QGIS/GRASS

*edited file links below I'm working on several NGO projects at the moment, all of which are reliant on being able to use a district level map with some 490+ features, and I am running into some ...
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72 views

header information is missing from image, after writing using opencv

I am doing complement of an image using open-cv python, while writing the image, open-cv is not writing the header information in the complemented image. my image data are in TIFF format. i am doing ...
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1answer
109 views

Is it a good idea to use GRASS Algorithms for Geoprocessing in a Server Environment?

I´m designing a web-service to run in a server environment that will do some geoprocessing actions to datasets uploaded by users and send the results back. I´m programming in Python, and so far I´ve ...
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13 views

GRASS Add Vector Point

I need to do a viewshed analysis using GRASS. I've got the DEMs loaded; and I simply want to input several (2-4) points (like 41.12345N, 122.34567W from GPS). What is the simplest, most ...
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2answers
415 views

Merge two rasters with no data value

I have two rasters: Raster A and B. Raster A has has only values of 0. The white area in Raster B are No Data values. I want to merge them to one raster (Raster C). So basically I want all pixels in ...
3
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2answers
2k views

1'' DHM: Hillshade is too rough - how to “generalize”?

I got this hillshade from my DHM (I used the hillshade-module from qgis). For my purpose there is too much relief detail (roughness). How can I get rid of this in QGIS or GRASS? Thanks! Martin
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42 views

Debug/Improve Performance of GRASS v.in.ogr

I'm trying to import shapefiles (in this case, OpenStreetMap data) into GRASS (grass70-svn) using v.in.ogr; and it is painfully, brutally slow. At first I thought this was because I was using the ...
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1answer
88 views

Is there a tool to buffer features with more than one distance value in GRASS GIS?

I´m looking for a tool like Multiple-Ring-Buffer in ArcGIS, but for GRASS GIS to be able to buffer with different distances but only having to start the process once.
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90 views

Analysing a network distance to two or more points using GRASS or QGIS

I am doing a piece of analysis work looking at distances along a network in GRASS. Most of the analysis involves finding which parts of the network are within 600m of a series of points. GRASS does ...
2
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1answer
2k views

How to find the watershed area for each point in the river network using DEM?

Update#1: Thanks, Micha, I have followed your instruction and successfully use the modules in GRASS. I use r.watershed to get the basin raster and the drainage line: and I use r.water.outlet to get ...
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1answer
281 views

How to get additional subbasin areas designated by points in the river network?

Update 14/1/9:I follow this post:Watershed and Stream Network Delineation, and here's my workflow: use Batch Point Generation to create batch points related to designated points(green dots) Batch ...
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68 views

QGIS V. parallel command using GRASS

I cannot offset a line to a specific decimal place, (ie only whole numbers can be inputted) Am I missing something here??
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1answer
53 views

grass on ubuntu cannot import globalvar

I installed GRASS GIS 6.4.3 on Ubuntu Precise 12.04 by sudo apt-get install grass grass-doc, as recommended by the Wiki. It runs with the wxpython GUI, but when I use any command (like r.in.gdal or ...
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61 views

How to use the Cartographic Composer of GRASS 6.4.3?

Following on from my previous question (which was, again, how to use the Cartographic Composer)... I've got a GIS in GRASS. I need to print various bits of it. Problem is, it needs images on it ...
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2k views

How to use GRASS module to delineate watershed area?

Update#1:I changed to work under qgis 1.8, I only input the DEM file and run the r.watershed module, and I got this: I have a DEM file of one specified region, and I take the following steps to ...
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1answer
198 views

Importing SRTM Data into Grass

I am having issues importing an SRTM HGT file into Grass. I first made a new location as the instructions from this Grass Newsletter Tutorial states. I then went to the download site and downloaded ...
2
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2answers
60 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 ...
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102 views

gdalbuildvrt ------— Problems with binary rasters used by grass

r.in.gdal is used for importing tif images in grass environment and they were changed to binary by default. I am trying to make a stack from them but unfortunately grass does not see my rasters ...
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731 views

Why is this SRTM TIFF not visible in GRASS GIS 6.4.3?

I want to use interpolated SRTM data for Germany to generate an STL terrain map for use in a CFD application. My SRTM data comes from the OpenDEM project. SRTM data normally has voids, but this data ...
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370 views

When trying to convert an .e00 file into a shapefile with ogr2ogr, getting “ERROR 4: This looks like a compressed E00 file”

When I ran this command: ogr2ogr topo.shp flowe86hyp.e00 I got this error: ERROR 4: This looks like a compressed E00 file and cannot be processed directly. You may need to uncompress it first ...
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1answer
81 views

How to import r.in.gdal from WCS (only region extent)

Can I import WCS-Data only for the current region by r.in.gdal? I tried to import raster data from my WCS into GRASS GIS, using r.in.gdal as proposed in ...
3
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1answer
136 views

Temporal GRASS GIS framework

I am trying to follow the tutorial posted here. When I get to this part "Extraction of seasonal mean temperature" and run this code: t.rast.extract \ input=temperature_mean_1950_2011_seasonal \ ...
2
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1answer
66 views

Isolate the largest patch in a raster in GRASS?

I have a raster with a series of patches (contiguous areas with same value). How do I isolate the largest patch? I know I could run r.stats, look through the long list of calculated areas, figure out ...
2
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1answer
274 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 ...
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1answer
169 views

How to fix QGIS crashes when using GRASS toolbox?

I've installed QGIS 2.0.1 on Ubuntu 12.04. exactly as explained on qgis.org . Unfortunately QGIS crashes when trying to use any GRASS model (r.aspect as example): just opening QGIS, click on toolbox ...
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1answer
518 views

What is the best way to ortho-rectificate image from the plane?

I am very new in GIS and I am trying to ortho-rectificate my images. But after putting it on the map I see that results are not precise. We have images taken from the airplane, it's longitude, ...
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1answer
92 views

Which Landsat version is appropriate to imply a supervised classification with GRASS GIS?

I need to imply a supervised classification with GRASS GIS to find build-up areas. I want to avoid Landsat 7 images due to SLC problem. Can I use images of Landsat 8 or it's better to use images ...
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78 views

Longest slope oriented to north?

I need a help with my homework. I have created digital elevation model from the shapefile. In QGis(Grass plugin) This is how far i can go. I have to find the longest slope oriented to North. I know ...
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1answer
118 views

Area of a Cross Section GRASS GIS 7

I have a task I would like to solve with GRASS GIS 7, if somehow possible. I want to create a cross section from a landslide - and would like to calculate the area of that cross section/profile. Any ...
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1answer
169 views

How to get the direction raster from r.walk or r.cost

I am trying to use r.cost and r.walk and r.drain to calculate the shortest path from an archaeological site to the nearest basalt source. I am using all this algorithms with the processing toolbox (I ...
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2answers
93 views

Two r.mapcalc calculations return a much bigger raster cell size than the input raster

I tried the following calculations with a GeoTiff sample, having a cell size of 25m: Calculating the togographic exposure (TOPEX) and estimating the mean topographic curvature Both, the resulting ...
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39 views

Unable to set pg as default backend with osgeo4w GRASS

I am trying to set PostgreSQL as default backend for GRASS, but cannot manage to get it right. Working with GRASS 6.4.3 print g.run_command('db.connect', driver='pg', flags = 'c', ...
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1answer
545 views

GRASS in QGIS not working (windows XP)

I am unable to use GRASS algorithms in QGIS 2.0.1 (on windows xp). I've already configured the GRASS path. The algorithms seems to work correctly (I cannot see errors in the log), however in the end ...
3
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2answers
250 views

Create network from shapefile without ArcGIS?

I want to perform shortest-path analysis on a network whose edges represent real-world roads and whose nodes are buildings or other locations. I have the shapefile for the area I'm interested in. ...
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77 views

Calculating vector statistics in GRASS

I have a points layer, each of points have an year attribute and I want to count how many points in each year. I use GRASS-GIS and its v.univar function: v.univar -e map=mod14_hmao column=year ...
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1answer
107 views

Calling GRASS 6 in GRASS 7 (shell)?

I am running a shell script for batch processing in GRASS 7 (calling it with sh [...sh] in the command line window), which creates a series of rasters through classifications, raster calculator and ...
0
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1answer
124 views

How to use v.to.3d in GRASS GIS?

I am trying to use GRASS GIS for the first time. After quite a lot of trouble I managed to create a location and a new mapset, and my shapefile is now displayed in the window "GRASS GIS Map Display" ...
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99 views

How to simplify osm2po's routable graph?

I'm building a pgrouting routable network thanks to osm2po, the problem is that my network is too big. Indeed I want to create isochron and 1 node = 1 canvas circle, so I don't want too many nodes. I ...
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1answer
94 views

GRASS has broken my terminal

I'm using GRASS on OS X. After installing GRASS I can no longer open my terminal to a prompt. On opening the terminal, the following line runs by itselt ...
3
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4answers
352 views

Has anyone else been unable to locate and install the GRASS plugin in QGIS 2.0.1?

After uploading and installing QGIS 2.0.1, I am unable to locate and install the GRASS plugin. The plugin is not listed in the 'Plugin Manager'. The 'Plugin_Installer' is also shown in red, ...
2
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1answer
69 views

Profile plot trouble in Grass GIS

I'm new to Grass and GIS environments in general, and I recently faced a problem when trying to get the profile plot from a DTM. When I draw the transect, instead of the plot, I get the following ...
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2answers
266 views

Processing area of interests within Grass GIS

I'm looking to process a region within a satellite image in Grass GIS. In ENVI I would create a region of interest (.roi) and then create a subset. Say, if I have co-ordinates for a rectangle within ...
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51 views

Problem with GRASS in QGIS

I am trying to import a vectorlayer to GRASS from QGIS. I get an error and hope someone here can help. Been trying to fix it for hours, but come no closer to a solution..... This is the error I get: ...
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142 views

Merging contour lines along tile boundaries

I am working with the CANVEC data set. The data in canvec is broken up in to mapsheets. eg. 116B04. I have data covering the entire province of the Yukon. I have merged all the data in to one ...
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161 views

How to install GRASS in QGIS Dufour?

How do I install GRASS to run in QGIS 2.0.1? GRASS is not listed in the Plugin Manager and attempting to access it via the Processing Toolbox gives me the following error:
2
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1answer
340 views

How to pansharpen radiance/reflectance Landsat 8 in GRASS 7?

first at all, I have to say that I'm new GRASS user. I would like to make a pansharp in GRASS 7 with reflectance Landsat 8 bands. I have revised some related posts and blogs, and I didn't find out if ...