Tagged Questions
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 ...
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?
...
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 ...
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 ...
3
votes
3answers
99 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 ...
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 ...
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 ...
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 ...
0
votes
0answers
206 views
How to resample a raster in QGIS?
I've got a boundary file that I would like to resample the raster file from a 30m grid to a 10m grid inside the boundary file. When I try and do it in Qgis or Grass all I get is one big raster cube ...
1
vote
1answer
72 views
Set certain amount of pixels to 1 inside of a polygon (GRASS)
I have a rather coarse vector map with polygons and want to calculate a (sufficiently) finer raster map defined by spatial extension and resolution. Every polygon of the vector map has a value ...
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 ...
3
votes
1answer
55 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
0answers
40 views
GRASS error reading raster map: request for row 1 is outside region [closed]
I'm a rather inexperienced GRASS user, and am trying to use an addon module called r.geomorphon (see http://sil.uc.edu/downloads.html#software). I've managed to get it installed and am trying to run ...
2
votes
1answer
118 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 ...
5
votes
2answers
293 views
How to batch import GDAL supported raster files into GRASS?
I am trying to import some GDAL supported raster files into a binary raster map layer using the r.in.gdal module from QGis Grass tool.
As I have multiple files to import, I would like to batch import ...
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 ...
1
vote
1answer
74 views
extract data from several images to different shapefile columns using GRASS
I am now working in grass and I want to extract raster values from several images to a shapefile. I have already created the columns in the .shp where the raster values will be stored but I am facing ...
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
1
vote
1answer
115 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 ...
3
votes
1answer
149 views
How to reproject a raster to Winkel Tripel projection?
I'm trying to project a raster map (in ASCII grid format) from longlat to the Winkel Tripel projection. But I'm running into errors, for instance gdalwarp won't accept the proj-string.
$ gdalwarp ...
1
vote
3answers
176 views
Determining gradient of road segment
I've a shapefile of roads data. It contains information about terrain of road segments, i.e., hilly, flat, undulating, etc. I want to determine gradient of every road segment. I know this might ...
2
votes
1answer
212 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
2answers
650 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 ...
4
votes
1answer
216 views
Multishading: bring them together to one Raster-Image
I made a multi-hillshade with 4 different light-directions and colors and stacked one above the other, each with its own transparency. Now I want to "save" the result in one raster-image.
Whats the ...
3
votes
1answer
382 views
Cell calculations; QGIS,GRASS,GDAL,SAGA
I recently asked a question about trying to calculate the slope over distance (manually) using QGIS, but then I came up with another way of solving the problem, but I would have to get some help for ...
1
vote
1answer
154 views
Why can't r.patch find the rasters?
I have elevation rasters which loaded just fine in a GRASS session. They represent adjacent areas, so I want to meld them into one raster.
I ran r.patch using the GRASS GUI, and it would only accept ...
0
votes
1answer
39 views
Does 'r.patch' act only on “loaded” rasters?
Can I run the GRASS command 'r.patch' on raster files which are not "loaded" into the current GRASS session? That is, rasters which are simply in my folder but not in a GRASS location & mapset?
...
0
votes
1answer
96 views
GRASS importing same-name rasters fails
I have NED elevation data in 3 rasters. (That's how it downloaded from USGS NED page.) The files are named "61471006", "61471006_2", and "61471006_3". I succeeded in using the GRASS GUI and menu ...
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 ...
6
votes
2answers
546 views
creating a raster of the residuals of a regression between two rasters
I am trying to create a raster of the residuals of a regression between two rasters. i.e. I would like to carry out a regression of one raster against another of the same extent and plot the residual ...
3
votes
1answer
257 views
Change raster value for an area based on a class of another raster
I would like to change all raster values in raster A that fall into the locations of category/class 1 of raster B.
Here, some more details. I did a calculation on a DEM resulting in different ...
5
votes
2answers
144 views
Vectorize cell boundaries in GRASS
I need to vectorize the cell boundaries of a raster map and I have forgotten how to do this.
For instance, if I have a raster map of a region that is just map=1 with a cell size of 500m, I would ...
1
vote
2answers
1k views
How to set cell size for vector to raster conversion in QGIS GRASS plugin?
I'm converting a vector (loaded in GRASS plugin in QGIS (1.7.0.-wroclaw) and would like to convert this to a raster with a defined cell size. At the same time I need a value from the attribute tabel ...
2
votes
2answers
171 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 ...
1
vote
1answer
122 views
Blank Vector Selection Dropdown in QGIS GRASS Plugin
I realise there are some issues which getting vectors into the GRASS module in QGIS, but is the behaviour i am getting expected?
I have loaded the vector shapefile via GRASS, closed G and reopened ...
1
vote
1answer
169 views
How can GRASS export an .flt file?
I am using GRASS and connecting it to another application. The other application needs an FLT file of the raster map which I should export from GRASS. The other application only reads FLT files. Can ...
8
votes
2answers
519 views
How to convert a vector boundary to a raster map?
I need to output a PNG file of a raster map overlayed with boundaries present in a vector map. The problem is, the r.out.png script only exports a raster map. My boundaries are in a vector format. ...
1
vote
2answers
404 views
How to import .flt files into GRASS?
I am trying to import a raster file (.flt) into GRASS. The raster file (.flt) was generated from HEC-RAS. The said raster format cannot be imported into GRASS (it shows the error "file not ...
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 ...
4
votes
1answer
546 views
How can I calculate the vertical distance to the nearest water?
Summary:
I would like to create a raster where each cell contains the vertical distance to the nearest water (a decent approximation would be acceptable). The problem is that I'm not sure how to go ...
1
vote
1answer
266 views
How to use r.patch with two maps having different colortables?
I am using r.patch to combine two raster maps in order to fill in the null values of the other. Is there a way to use r.patch but still maintaining the colortables of the separate raster maps? I do ...
4
votes
5answers
458 views
How to save a raster and vector into a single PNG file in GRASS?
I am trying to save a raster and vector into a PNG file. The vector is overlayed on top of the raster map. I was only able to save the raster file into a png using r.out.png but without the vector.
5
votes
2answers
1k views
How to return raster values based on polygon (shapefile) boundaries in QGIS?
How to return raster values based on polygon (shapefile) boundaries in QGIS?
Is this an elementary question, because I am finding it hard.......
Ideally I would like a neat workflow as I am likely to ...
6
votes
1answer
347 views
How to modify the colors of a raster map to use only one color in varying shades?
I have a raster map in GRASS containing elevation values. I want to display the elevation values in only one color (specificaly blue) but in varying shades of blue. I tried the options in r.colors, ...
3
votes
1answer
184 views
Problem in r.resample
When I run r.resample to crop a map by using a vector and a mask, the resulting map has the same shape as the vector that I used but does not replicate (exactly) the portion of the raster map that I ...
3
votes
2answers
627 views
How to delete a base map in GRASS?
I'm trying to delete a map that I used as a mask before, but I cannot delete it using g.remove. It displays this:
g.remove rast=raster_Mnorzagaray@PERMANENT
[raster_Mnorzagaray@PERMANENT@PERMANENT] ...
7
votes
1answer
635 views
GRASS - Will r.to.vect work on this scanned map?
Total GRASS noob here. I have several very large hand contoured maps to digitize, and this thread intrigues me. In the past I have spent hours upon hours digitizing these maps and revisions in ArcMap. ...
0
votes
1answer
178 views
How to export a png file from a raster file? r.out.png has an error
I used r.out.png to export a png file, but it produced this error:
(Sun Feb 27 00:26:32 2011)
r.out.png input=raster_bulacanElevation ...
3
votes
1answer
407 views
Is there a way of cutting a raster map that is displayed in the GRASS GIS Map Display?
I have a raster map that I generated from cropping/masking from a bigger raster map. It produced a map with only a portion of not null values. I only want to have a map that is zoomed in to the ...
6
votes
3answers
1k views
R: Download a large DEM, change projection, and adjust to smaller scale
This is a process that takes just a few seconds in GIS software. My attempt to do it in R uses a large amount of memory then fails. Is there something wrong in my code, or is this just something R ...
