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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2answers
75 views
Handling MODIS NoData cells with gdalwarp
I'm using the gdalwarp tool to convert MODIS .hdf into GeoTiff files. I want to set the value of the nodata cells so that when I import the .tif image into Grass there is no black edge. I'm using the ...
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0answers
76 views
qgis plugin: “WindowsError: [Error 6] The handle is invalid”
OS: Windows 7 64bit
GIS: QGIS 1.8 (qgis.org/downloads/QGIS-OSGeo4W-1.8.0-2-Setup.exe)
path variable:
GISBASE=C:\Program Files (x86)\Quantum GIS Lisboa\apps\grass\grass-6.4.3RC2
...
0
votes
1answer
78 views
import grass.script as grass under windows 7
OS: Windows 7 64bit
GIS: QGIS 1.8 (qgis.org/downloads/QGIS-OSGeo4W-1.8.0-2-Setup.exe)
I have created a plugin for QGIS, with the QGIS plugin builder.
Now i would like to import grass.script into ...
2
votes
0answers
53 views
How to join nodes to network lines ( and not the other points)
I'm trying to do a shortest path analysis on my network. In order to prepare the network and attach polygon centroids to the roads, I used GRASS' V.NET operation=connect. the problem with this ...
2
votes
1answer
38 views
Help with GRASS V.Net.Path
GRASS has extensive and brilliant documentation, but I still have a bit of trouble using v.net.path. in the example for shortest path, it says: "
#Shortest path: ID as first number, then cat1 and ...
1
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0answers
59 views
GRASS Plugin to QGIS error
I am installing QGIS and GRASS as part of an FOSS GIS class I'll be teaching this summer. I used the OsGeo4W installer. This installer has always worked flawlessly for me except on the machines at the ...
3
votes
1answer
99 views
How to split line at a specified distance and getting coordinates of start and end points of each line segment？
I tried v.split in GRASS：
and my notebook ran a lot of time but showed this error：bad allocation, then I click "OK", and got nothing.
Are there other ways to split lines？and I hope to get 2 new ...
0
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1answer
39 views
Grass 7 - where is r.regression.multi hiding?
I compiled Grass 7 on Ubuntu and all works fine - except, I cannot find r.regression.multi. I installed it, yet it is nowhere to be found in the drop-down menus; r.regression.line is there and works, ...
7
votes
1answer
242 views
Can I use GRASS algorithms in Sextante under ArcGIS?
Sextante for ArcGIS comes with SAGA modules.
I know that I can use GRASS algorithms in Sextante under gvSIG.
But how can I use GRASS algorithms in Sextante under ArcGIS? I tried to look for any ...
2
votes
0answers
84 views
Flow modeling and FOSS GIS; lahars and HEC-RAS
What are the options for FOSS flow modeling of dilute debris flows in QGIS or GRASS?
Have you, or can you refer me to studies where the authors, tested these models/plugins/functions/etc. for use in ...
1
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0answers
42 views
How to create the fuel models & live fuel moisture rasters for Wildfire simulation?
Has anybody done wildfire modelling in GRASS? Where could I obtain / how do I create the fuel models and live fuel moisture rasters to determine rate of spread (r.ros)?
1
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1answer
132 views
v.dissolve renames the attribute table column and does not produce a dbf
When I run v.dissolve on my vector...
v.dissolve --o input=pass2@mapset1 layer=1 column=fttcp output=pass3
The dissolving appears to work but the column name in the attribute table has changed from ...
2
votes
0answers
42 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 \
...
1
vote
1answer
82 views
How to remove terracing from Civil3D GeoTIFF export?
I've received a GeoTIFF DEM that was exported from Civil3D and at every contour there is a distinct terrace created when I process an aspect or slope in QGIS with the GRASS plugins.
I've looked ...
0
votes
3answers
145 views
How to rasterize a vector map?
I am looking for a way to create a raster grid from a vector map.
I have a map consisting of shapefiles which I want to export as a raster with UTM coordinates. I was thinking of something using the ...
1
vote
1answer
66 views
Grass 7 .las data import problem
I compiled Grass7 on Ubuntu 12.10, with liblas in order to run r.in.lidar and v.in.lidar. I now want to import .las data; the option in file -> import raster data -> LAS LIDAR points import is given ...
3
votes
3answers
101 views
query raster cell values by point
I have a binary raster (0s and 1s) that I need to query given a set of point coordinates. This is easy enough to do with gdal (gdallocationinfo), but where it get's complicated is that I also need to ...
0
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0answers
89 views
Help in GRASS/QGIS/Python
I have Idea about ArcGIS, and a bit of QGIS and zero programming knowledge, which I am trying for thesedays. I saw GRASS GIS and have started working with shapefiles, which are not being loaded... :( ...
3
votes
2answers
62 views
How do I tell GRASS where to find Python?
For some reason, when I start GRASS on my Mac it says that it has found Python 2.6.7. However, /usr/bin/python version is 2.7.2 and I can't find a lower version anywhere on my system. Potentially ...
0
votes
1answer
59 views
Data management in GRASS from command line?
I'm trying to import a large set of raster files into GRASS. The GUI import tool works fine for a handful of files, but it appears to require that I click the "Layer id" checkbox for each individual ...
0
votes
1answer
29 views
Why is this GRASS script (from GRASS WiKi) causing an error?
I'm trying to run a script from the GRASS WiKi to create a simple map using ps.map. I'm confused because it's generating an error that the output was not set, when it appears to me that it is set at ...
1
vote
1answer
82 views
How to invert polygons (or other options for exterior styling)?
I have a shapefile containing many polygons that I want to use to mask a raster. I have tried gdalwarp -cutline <shapefile> -crop_to_cutline -srcnodata -9999 -dstnodata -9999 ...
0
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0answers
43 views
Add GRASS Addon to Sextant within QGIS
I have successfully installed r.viewshed as an add-on in GRASSS 6.4.2. I would like the command to show up in the list of algorithms within Sextante. Is there a way to make Sextante "aware" of ...
2
votes
1answer
66 views
V.kernel not working correctly in grass-6.4.2
I am using grass-6.4.2 for generation of heat maps of crime data. For testing purpose, I created a vector layer from my places shapefile which is a point data.The places shapefile contains more than ...
2
votes
1answer
33 views
r.neighbors produces no output
I am running
r.neighbors --overwrite --verbose input=bf03pits@PERMANENT output=bf03pitsdenoise method=mode size=5
in the GRASS GUI using the r.neighbors dialog.
bf03pits has 3955848 all with ...
2
votes
1answer
48 views
Is it possible to use a WHERE clause with Grass v.in.ogr for DGN sources?
I am trying to import a .DGN with Grass v.in.ogr in QGIS. I am able to import the DGN perfectly, but I would like to filter the elements using the WHERE option. From searching, reading and testing I ...
2
votes
1answer
44 views
d.rast.edit error when attempting to edit a raster
I always get an error when I try to edit cell values in a raster with the GrassGIS command „d.rast.edit“.
The error under Windows XP/GrassGIS 6.4.3 says:
Exception in thread Thread-29:
Traceback ...
2
votes
0answers
116 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 ...
1
vote
1answer
116 views
Why is transparancy of GRASS rasters missing when imported into QGIS?
I have a raster map in QGIS imported from a GRASS mapset with the QGIS GRASS plugin. The problem is that I have null() cells in the GRASS map that appear "colored" in QGIS. How can I set the ...
1
vote
1answer
99 views
Grass v.clean.snap with Polygons
I am doing some topology testing using Grass in QGIS. I am hoping to snap nodes to eliminate gaps between polygons. When I use the v.clean.snap function in Grass it does not work on polygons. When I ...
0
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0answers
72 views
Free and Open Source GIS Desktop Dissertation Survey – Participants wanted [closed]
I am currently in my last year of MSc Information Technology course at the University of the West of England. I am required to undertake a dissertation project. I am conducting a study on the level of ...
0
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1answer
33 views
GRASS: Loss of data using v.net
I'm trying to build a network in GRASS in order to find the shortest path from any settlement out of 1120 (points), to one waste treatment facility out of 27 (points). I plan to use v.net.distance ...
4
votes
1answer
134 views
How can I avoid reprojection gaps when merging DEM rasters?
I have two raster DEMs in same resolution I want to bring together. I was using the merge-function in SAGA, GRASS and QGIS but I always get the following result:
What do I need? Where could the ...
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0answers
43 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 ...
6
votes
1answer
635 views
How to calculate difference in altitude along lines using GRASS?
Using SRTM altitude information and OpenStreetmap roads, I want to calculate altitude differences (sum of meters uphill and downhill separated = two values) per road element.
What would be the ...
0
votes
0answers
28 views
Why are there strange black and white rows and columns in my aspect map?
I would have a problem with aspect map in GRASS. I'm not an expert, so I think you easily can help me. I have created this aspect map, from dtm, but the result was an image with strange black and ...
4
votes
2answers
86 views
How to do a looping to Interpolate a huge Rainfall Time-series in GRASS GIS or R
In GRASS GIS I have access to a table in PostgreSQL Database with this structure:
Table Name: rainfall_time_series
Columns: id | year | month | day | value_mm | x | y | gauge_code
Setting g.region ...
4
votes
1answer
84 views
Programmatic raster-vector calculation
I currently use GRASS' r.mapcalc to find the difference between vector and raster data using a loop and temporary files and layers.
Is it possible to do the core calculation between raster with a ...
1
vote
1answer
152 views
Rasterize vector with gdal
"I would like to calculate the Euclidian distance from a residence to a public service of interest e.g. the distance from a residence to a green space (as the crow flies) in QGIS. After browsing the ...
2
votes
0answers
88 views
Export to shapefile qgis
I am trying to develop hotspot map showing point density in our gis based web application. After searching for an option I have decided to use v.kernel command. I have a table containing some point ...
8
votes
4answers
2k views
Code to calculate elevation profile along line from a DEM
Given a DEM (Digital Elevation Model) say in and a line (x1,y1) --> (x2,y2) (paired coordinates (x,y)), how can one calculate the elevation profile or cross-section projected on that line ?
I am ...
2
votes
1answer
38 views
grass gis- ERROR: nwalk (7000001) > maxw (7000000)! [closed]
i want to make r.sim.water (hydrological modelling) in Grass Gis, and this ERROR: nwalk (7000001) > maxw (7000000)! always appears, any ideas how to solve it?
number of cells of dem is below 7000000.
...
0
votes
1answer
107 views
QGIS, Euclidean distance analysis [duplicate]
i wanna generate euclodian distance map for my road data. I 'll use it for multi criteria analysis. I can get it by using Arcgis Euclodian Distance tool but i wanna generate it in QGIS environment. I ...
3
votes
2answers
57 views
Is there a workaround for GRASS i.maxlik 'class' being a keyword in Python?
I am running i.maxlik in python - attempting to automate a processing chain.
I use the command:
grass.run_command('i.maxlik', group= group, subgroup=subgroup, class='classification', sigfile = ...
1
vote
0answers
17 views
How to remove coastlines from Admin 0 data set using GRASS?
I have a set of international borders that I would like to overlay on top of a different data layer that represents coastlines ("land" essentially). I would like to convert my Admin 0 polygons into ...
1
vote
3answers
57 views
How do I active “Open GRASS tools”-button?
I have opened to GRASS layers and need to use the "Open GRASS tools"-button. This button remains unactivated somehow. Whilst the "Edit GRASS vector layer" right next to it works perfectly fine. What ...
3
votes
1answer
56 views
GRASS r.grow doesn't seem to change raster values at all
I have a raster map in GRASS that looks like this:
The red cells have a value of 1, the yellow cells have a value of 0.
I am trying to use the r.grow command to 'fill in' the gaps in the red ...
1
vote
1answer
132 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 ...
2
votes
1answer
36 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 ...
1
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0answers
85 views
Heat Map trouble: Is this a data formating problem?
I'm playing with the heat map plugin with QGIS. I've run through QGIS tutorial:
http://docs.qgis.org/html/en/docs/user_manual/plugins/plugins_heatmap.html,
using the airports data set as explained ...
