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
3answers
215 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.
...
2
votes
2answers
206 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 ...
2
votes
1answer
523 views
How to create a Digital Elevation Model
How to create a DEM starting from layers shapefile "contour lines" and "shares"?
which module of GRASS I need to use?
thanks for yours responses....
2
votes
2answers
457 views
1'' DHM: Hillshade is too rough - how to “generalize”?
I got that hillshade from my DHM (I used the hillshade-module from qgis). For my purpose there a too much relief details (roughness). How can I get rid of them in QGIS or GRASS?
Thanks!
Martin
2
votes
2answers
595 views
How to delete a map from the GRASS interface?
I want to delete a map that I generated from GRASS. I tried removing a map from the "Map Layers for each display" tab in the GRASS GIS Layer Manager, but it only removed the map from the list and not ...
2
votes
2answers
116 views
2
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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
1answer
661 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 ...
2
votes
2answers
287 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
votes
1answer
85 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
2answers
138 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, ...
2
votes
1answer
89 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 ...
2
votes
1answer
32 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
177 views
Integrated viewshed analysis
I need to do integrated viewshed analysis of a target with several observer locations. I am going to use r.viewshed analysis function in GRASS. With this function, it is possible to perform analysis ...
2
votes
1answer
196 views
Is it possible to produce a decent looking shaded-relief map at 50K-scale-or-larger using SRTM3 DEM?
I'm trying to make a decent-looking shaded-relief map of a particular area in 50K-scale-or-larger using open-source tools. The best (and free) option I have for DEM data for that area right now is the ...
2
votes
1answer
46 views
What units are used in GRASS Rasterize?
What units are used in GDAL Proximity or GRASS Rasterize?
- 'new size' parameter
2
votes
1answer
342 views
How to join two polygon layers into a resulting layer with overlapping polygons merged together (including attributes)
I am trying to find a method (in QGIS and/or GRASS) to join two layers of polygons into a resulting layer with merged overlapping polygons. It's hard to explain in words, so I've drawn a simplified ...
2
votes
1answer
365 views
How to enable GRASS plugin in QGIS 1.8.0 (Linux Mint 13 - 64 bit)?
Every time I enable GRASS plugin in QGIS (Plugins -> Manage Plugins -> GRASS), I got a message: Exception - G_getenv(): Variable GISDBASE not set.
I googled and found some information here but don't ...
2
votes
2answers
127 views
River drain: r.watershed to vector is not working
I want to vertorize the result of r.watershed (accumulation). After using r.to.vect I got the message that I have to use r.thin before. So I did, but the message comes again and again.
What I am ...
2
votes
2answers
2k views
Viewing .las format LIDAR data in QGIS?
Is there an easy path to visualizing this LIDAR data? I have QGIS, and some USGS LIDAR data in (.las) format downloaded from http://lidar.cr.usgs.gov/ . This means I have both the (.las) and ...
2
votes
1answer
284 views
Compilation of GRASS 6.4.trunk on Win7
you may have seen my other posts, at the point now where I am trying to use the landsat plugins in a lower version of GRASS. Markus N noted that the 6.4.2 might be better, since that is not out yet I ...
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.
...
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 ...
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 ...
2
votes
1answer
114 views
How to filter or query data in GRASS?
I have a PostGIS dataset with just over 2 million rows. Each row has a PostGIS geometry point value and several attributes.
I'd like to do some analysis on certain subsets of the data, but I can't ...
2
votes
1answer
59 views
How to close and fill Gulfs and inlets in QGIS or Grass?
I have a raster layer from which I extracted only zones with a certain color, then polygonized it with QGis. I just generalized the new vector layer in GRASS to smooth things a bit.
There are many ...
2
votes
1answer
117 views
Raster Analysis - Identifying features from Raster
I have an IDW, tension spline and hill-shade rasters that show an archaeological landscape and from these rasters I want to identify new features which are seen in the landscape as depressions. And ...
2
votes
2answers
61 views
How to rasterize vector data correctly in GRASS GIS 6.4.0?
I try to rasterize some vector data in GRASS GIS 6.4.0. Unfortunately, it always just works with one layer. Afterwards, there are just lines generated instead of rectangles. What am I doing wrong?
2
votes
2answers
971 views
How to convert a point grid to a raster?
If I load the original .csv file, I then have a map of the African continent represented by 14069 data points covering it at 40x40km resolution. Each data point shows solar radiation means across the ...
2
votes
1answer
211 views
How to overlay my interpolation within the boundaries of Quebec?
I am trying to create interpolated maps within geographical borders.
I have the coordinates and values to the points I am trying to interpolate. I also have a map of the geographical land mass in ...
2
votes
1answer
186 views
Silence user warnings for GRASS-PYTHON program
I've created a program that runs externally from GRASS v6.4.1, using python 2.6. It imports an ESRI shapefile, and exports a seperate KML for every polygon in this vector file.
Polygons with ...
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>, ...
2
votes
1answer
317 views
Scripting in GRASS
Can anyone suggest me web-links to learn scripting in GRASS GIS (its utilities, examples etc.) other than those available in GRASS official Wiki/Sites?
2
votes
1answer
405 views
How to clean vector segment intersect errors in GRASS
I'm using GRASS to process a vector map.
When I export back to .SHP and do a 'Check Geometry Validity' in Quantum GIS it lists several errors of this type...
3,segments 199 and 203 of line 0 ...
2
votes
1answer
141 views
Error in using/installing v.digit: GRASS GIS
When I wanted to edit a shapefile in GRASS I got this message:
Unable to start wxGUI vector
digitizer. Do you want to start TCL/TK
digitizer (v.digit) instead?
Details: No module named
...
2
votes
1answer
416 views
How to import SpatiaLite data into GRASS?
How can I import SpatiaLite tables into GRASS? Are there any restrictions I should be aware of? How does GRASS cope with columns that don't have a specific type (Sqlite tends to create such columns ...
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
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.
...
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 ...
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
1answer
190 views
How to delete rings automatically using QGIS/Grass
I'm cleaning up a (very) messy shapefile in QGIS/Grass.
I now have several large polygons with numerous (100s) of small rings.
Is there a quick and easy way to remove/ fill all these small rings. ...
2
votes
1answer
264 views
How to correctly merge layers with overlapping polygons in QGIS/GRASS?
I have 4 vector shapefile that I would like to join/merge, without worrying about attributes.
Here are the shapefiles.
I would like to do an union and a spatial dissolve, but everytime I do a dissolve ...
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
2answers
276 views
Error Importing dbf File Into GRASS
I am working on an assignment which requires me to connect to a database, then import a dbf file into the database using the command db.in.ogr (as can be seen below). However, GRASS simply won't ...
2
votes
1answer
206 views
Using nviz module in GRASS through qgis error
I'm an new user to qgis/GRASS and I've run into a problem with the nviz module.
In trying to visualise a raster heat map created from vector contours in 3D using the nviz module in GRASS tools in ...
2
votes
2answers
647 views
How to vectorize a Raster-Classification? (qgis, grass)
I classified my raster-DHM into elevation levels using colormap. Its not a "real" classification, just a colormap. So I cant vectorize the classes to get polygones for every class.
Whats the best ...
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
108 views
Why is GRASS not thinning a terraflow raster properly?
I want to convert a raster map encoding directional flows (the output of r.terraflow) to a vector map. I'm using r.thin to process the output. It terminates successfully with 0 pixels removed during ...
2
votes
2answers
487 views
How to query data from a vector map (shapefile)?
We want to obtain the specific place of the boundaries of a shapefile. We want to be able to get the points of each polygon corresponding to a specific place in order to use these data in an ...
2
votes
0answers
77 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 ...
