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.
2
votes
0answers
23 views
How to create a topologically correct dataset in PostGIS (with GRASS)?
I have shapefiles which I have loaded in postgis and now i am trying to use geometric function in postgis like ST_intersect and they fail because the data is not topological correct.
I have tried to ...
2
votes
2answers
336 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
votes
2answers
223 views
run r.stats as a quiet module in GRASS-Python script
Has anyone else used r.stats as a quiet module in a GRASS-python script?
As part of my program I'm using:
grass.run_command("r.stats", flags='l', input=<file>, output=<*.csv file>, ...
0
votes
1answer
30 views
Problem opening GRASS GUI: libgeos-3.3.6.so: cannot open shared object file:
I have been using GRASS to process some Landsat imagery but very recently, and as far as I am aware - after having done nothing different or changing the settings, I am trying to use GRASS and on ...
14
votes
3answers
283 views
How to do kernel density estimation with a physical barrier/ boundary in QGIS?
Does anyone know of a programme that will allow kernelling that takes a boundary into account in its calculation rather than simply masking areas that are impossible?
So far I have found:
GME add on ...
0
votes
0answers
25 views
GRASS - Creating an Attribute Based on Driving Distance
Is it possible to calculate the driving distance for each node of one layer (fire stations) to each node of another (address points)? After doing so, I need to sort all of the distances from shortest ...
0
votes
2answers
45 views
How to align directions of connected lines?
I have a vector line made of different pieces of lines with different directions. I merged the lines to one. But this merged line still have different direction in its "invisible" parts. I want to ...
0
votes
0answers
53 views
Grass won't import shapefiles
I have a problem involving the import vector data command, specifically importing shape files. I installed QGIS on a pc at work and there I could import shape files into GRASS GIS 6.4.3RC2 (which is ...
2
votes
1answer
60 views
Issue while running grass from subprocess
I have a map based web application using geodjango. I needed to display the crime hotspots within a selected polygon area. I found that v.kernel is very good for generating heatmaps/hotspots. So in my ...
1
vote
1answer
44 views
Grass7 - r.regression.multi and new raster
I am on the learning curve with Grass7. I managed to make r.regression.multi work, but there is one thing that would be of high interest for me: it is possible to create a new raster showing the ...
0
votes
0answers
48 views
Why don't libgrass.so.1.8.0 and libqgissqlantconnection.so.1.8.0 load?
I have compiled Qgis 1.8 at Ubuntu 12.10, but some phyton plugins does'nt work, like sextante.
Trying to solve this problem, some files don't have been load. They are: libgrass.so.1.8.0 and ...
0
votes
1answer
106 views
How do you use 'reclass' in GRASS?
It could be user error, but for some reason, the reclass tool is just hanging and hanging...
QGIS 1.8
Compiled against GDAL/OGR 1.9.2
Ubuntu 12.04.1
Running the tool from the Sextante toolbox
Input ...
3
votes
1answer
77 views
Autocorrelated DEM with QGIS or Grass
I was wondering if there is a way to make an Autocorrelated DEM within QGIS or Grass. I am looking to do this with stereo aerial photography. I am able to do this with a number of COTS tools, but I ...
1
vote
1answer
52 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 ...
4
votes
1answer
75 views
Help installing add-on in GRASS, I get an error message
My Grass gives me this error message, Grass_info_error(4816,1):'make' required. Please install 'make' first. This happens when I attempt to fetch an add-on (r.viewshed). What am I doing wrong? and ...
2
votes
1answer
298 views
QGIS is not able to find GRASS. Choose the path of installation folder of GRASS
I've downloaded and then correctly installed QGIS 1.7.4 for windows (Win 7 64bit is my version) in C:\Programs\Quantum GIS.
But everytime I start QGIS this popup appear: "QGIS is not able to find the ...
2
votes
1answer
65 views
GRASS : r.resamp.rst error : “Not enough disk space--cannot write files”
Today, I am confronted to a difficulty I cannot manage.
When I try to use the tool "r.resamp.rst", it gives me as answer:
*r.resamp.rst input=map@PERMANENT ew_res=11 ns_res=11 pcurv=curv
...
0
votes
1answer
79 views
Sextante grass folder incorrect?
What is the correct grass folder in Sextante? I alway get this message:
The specified GRASS folder does not contain a valid set of GRASS
modules. Please, go to the SEXTANTE settings dialog, and ...
1
vote
1answer
69 views
QGIS contour lines shapefile to DEM help
I want to create a DEM from depth contours (shapefile) in QGIS. I've been trying to work out how to do this based on this previous question, notably from this link from that page, however I'm stuck, ...
1
vote
1answer
418 views
Is there any pseudocode for MFD (multiple flow direction) algorithm available?
Still stuck with the simulation system, is there any good pseudocode for the multiple flow direction (MFD) algorithm? I read a pseudocode example and implemented it, however the simulation was linear: ...
1
vote
0answers
23 views
GRASS v.overlay.or Error when trying to split a polygon with a line
I am using the Grass plugin in QGIS for Windows (1.8.0). I am trying to split a polygon with a line feature. I am using the v.overlay.or function within the QGIS Grass plugin. I have the line layer ...
1
vote
2answers
39 views
contour lines from point shape attribute
I have a point shape file and one of the attribute refers to the altitude.
Is is possible to obtain a contour lines shape file in GRASS?
0
votes
0answers
27 views
SEXTANTE “could not load layer:…”
When I try to do a GRASS command via SEXTANTE in Qgis I always get the error:
"Could not load layer:...." check log file
Does not matter wether it should be saved in temp or another folder.
I found ...
1
vote
1answer
39 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 ...
0
votes
2answers
97 views
Grass 7 / ArcGIS 9.3 - tiff to raster
Again a Grass 7 question. I have the output of a modelling run as matlab file, which I can export as tiff and load as geotiff. OK - now can I extract the data/convert this tiff into a raster proper?
...
10
votes
2answers
243 views
What's the relation between QGIS and GRASS?
I have been working with GIS and remote sensing in an university and professional environment some ten years ago (ArcInfo etc), so I have some experience even though somewhat outdated
Right now I am ...
4
votes
1answer
114 views
How to repair and clean contours from high data resolution (lidar)?
I'm unsuccessfully trying to make a bathymetric map with contours extracted from Lidar data at 1 m resolution.
The extracted contours have a lot of artifacts like dangles and islands.
First I used ...
2
votes
3answers
105 views
How to clean layers from non topological databases?
I'm doing my internship in a consulting office which is switching from MapInfo to QGIS/GRASS 1.8.0.
I posted here a few days ago about the way to clean a polyline from a Lidar data with v.clean.
...
0
votes
2answers
60 views
GRASS: populating attribute table with specific values
I have a vector map that includes 100 points. These points were created using v.extract to randomly sample a larger map of 10k points. As such, the 'cat' values range from 1 to more than 10k. What ...
0
votes
2answers
84 views
How to resolve missing Python module (importlib) for GRASS/Sextante?
I have installed the nightly build of QGIS 1.9 from Larry's Dakota Cartography site, and have downloaded the latest Frameworks from William's Kyng Chaos site.
However, I am unable to install the ...
5
votes
5answers
445 views
How to calculate distances in a point sequence?
I'm looking for help calculating the distance between a sequence of points that are in a single Shapefile in QGIS. Below is what my data look like and a blank distance column I've added to show how ...
5
votes
2answers
457 views
How to compile QGIS with GRASS on Ubuntu?
I am on Ubuntu building qgis with grass plugin. I have build grass code separately and used --prefix to provide the path
GRASS_PREFIX is /usr/local/grass-6.4.2 and GRASS_INCLUDE_DIR is ...
0
votes
2answers
59 views
How do I reproject one raster to match another's in GRASS
I have two raster layers, A and B, which have information about the same location but have different projections and datums.
How can I reproject layer A to match the projection and datum of layer B?
...
1
vote
1answer
34 views
r.regression.multi - ERROR: Not enough valid cells available
I am running a few analyses with r.regression.multi in Grass 7. For a few rasters that I try to correlate, the following error comes up, however: "ERROR: Not enough valid cells available".
I cannot ...
6
votes
4answers
415 views
Calculate polygon field based on neigboring polygon attribute
I have a vector shape with many different sized polygons each possessing an own class name (for instance "houses", "houses with offices", etc ...)
I want to assign a new field to each polygon ...
2
votes
1answer
53 views
How to get started with GRASS shell?
I'm a beginner in programming but i have to work with GRASS at work, and do it quickly.
I'm completely lost with all the variety of tutorials that are existing and to me, don't look the same...and ...
0
votes
1answer
40 views
Why can't I load more than 12 elevation files into NVIZ?
I have a large set of rasters in a GRASS mapset, which I would like to use as frames in an animation, visualizing the raster data as elevation. NVIZ is an obvious tool for this, but I'm having trouble ...
6
votes
1answer
229 views
How to perform unsupervised classification of LANDSAT time series using Grass?
I'm using GRASS to perform an unsupervised classification on a time series of LANDSAT images (monthly temporal res, over 30 years), in order to compare land cover change in a particular area.
I'm ...
0
votes
2answers
77 views
Error from ps.map in GRASS. How to fix?
I'm trying to learn how to use ps.map in GRASS. I thought that running it in interactive mode from the command line would be a good place to start, but I'm getting the following error:
> ps.map ...
1
vote
1answer
29 views
GRASS: shift point locations in a random direction
I have a vector map that contains 100 points. For each point, I would like to shift it 250 units in a random location. It's easy enough to shift all points in a specified direction using
v.edit ...
3
votes
1answer
202 views
How do I find vector line bearing in QGIS or GRASS?
How can one extract the bearings from a set of lines in a vector file?
I'm trying to find the bearings of several straight vector line segments (simplified contour lines, actually) and can't figure ...
7
votes
3answers
200 views
Howto setup and use a remote GIS workstation (QGIS,GRASS,PostGIS)?
I'm using QGIS (and sometimes GRASS and PostGIS) on my 2009 MacBookPro for my thesis project.
I was wondering (during an endless batch generalizing in QGIS) if I can set up a server so I can work from ...
0
votes
1answer
23 views
GRASS GIS: red square around node topology information?
I've been using GRASS since 2005, but I cannot find an explanation to the square boxes that appear around the nodes of a lines layers, when I display topological informations on the map.
I thought ...
0
votes
0answers
45 views
HELP! Starting up GRASS - Error messages.
I am just trying to start using GRASS, but am having problems setting up.
This is the error message I get:
WELCOME TO GRASS Version 6.4.2 2012
1) Have at your side all ...
0
votes
1answer
30 views
Full Easting and Northing coordinates values cannot be encoded in GRASS r.water.outlet in SEXTANTE-QGIS
The Easting or Northing coordinate parameter accepts only 5 digits. The Easting and Northing values for my outlet are 6 and 7 digits long (integer). How can they be encoded in r.water.outlet? Can ...
0
votes
0answers
20 views
query for adjacent polygons in GRASS?
i need to create a table of each district in india's adjacent districts.
i found this query but couldnt get it to work for me: SELECT p1.PK_UID, p1.Name FROM Polys p1, Polys p2 WHERE p2.PK_UID=1 AND ...
2
votes
1answer
90 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 ...
3
votes
1answer
58 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 ...
0
votes
2answers
72 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 ...
0
votes
0answers
74 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
...
