Tagged Questions

1
vote
1answer
41 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
46 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
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
votes
1answer
108 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 ...
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 ...
6
votes
1answer
197 views

Generalize large polygon-file

I have a large polygone file with landuse information (6 classes). Its vectorised from a raster classification so the polygons are all angular. Any of my tries to generalize with v.generalize (sneaks, ...
5
votes
2answers
464 views

How to compare two DEMs and show their difference?

I want to compare my DEMs (ASTER GDEM2 and SRTM4.1). I know, that the GDEM has some extreme "holes" with totaly wrong elevations (I found 3 of them in my working area). Now I need to know, if there ...
5
votes
2answers
638 views

How to smooth large vector polygons from Raster

I have a landuse classification raster file (6 classes) of a large area. But I need it in vector polygons so I vectorised it. No problem so far, but the result is - of course - that every pixel is ...
4
votes
4answers
416 views

How to generalize and vectorize a LandUseClassification raster file?

I want to vectorize that rasterfile with its 6 landuse classes. The classification is very noisy and have to be generalized before. The result should be a polygone vector file. I use SAGA, (GRASS) ...
3
votes
3answers
208 views

Topographic correction (for land use classification) with SAGA or GRASS

Is there a module in GRASS or SAGA (or a alternative open program) to do a topographic correction of a landsat image to enhance the land use classification? Thanks! Martin
7
votes
2answers
454 views

Is it possible to manually correct a raster DEM (OpenSource)?

Is it possible, to correct a raster DEM by changeing the raster-cell-values manually, like by "painting"? My DEM (ASTER) have one small error where the elevation is about 300m below the actual ...
1
vote
2answers
444 views

Interpolation of contours (from one “main-contour-shapefile”)

I calculated, that the best and smalest possible äquidistance (equidistant) for my map is 30m. After I generlized my DHM, I extracted contours of a intervall of 30m and smoothed them. Now I have my ...
4
votes
4answers
453 views

How to automatically plot intermediate contours with QGIS, GRASS GIS or SAGA GIS?

I'm mapping a steep mountain range. My main contour interval is 50 m and my intermediate contour interval is 10 m. In steep areas, the interval of 10 m is too small, so I need to leave ...
4
votes
2answers
460 views

Altitude Above channel in GRASS 6.4

i'm fairly new to the GIS world and GRASS (come from econometric background), i would like to do some species distribution modeling using R and GRASS. So i started to read the book of Tomislav Hengl ...