1
vote
1answer
39 views

QGIS DEM (Terrain models) Mode Slope creates wrong data [duplicate]

I have a DEM raster file downloaded from the USGS site. The file can be downloaded here. I am trying to create a slope raster in percent with the DEM tool in QGIS. The GDAL command is the following: ...
3
votes
2answers
81 views

Merging DEMs of different grid size

I'm trying to merge two grids with different cell size. One has a cell size of 10m and the other 50m. The 10m one covers a subarea of the 50m one. I know that the most accurate one is the 10m one and ...
2
votes
2answers
79 views

How to produce a CSV file from .tif file with elevation data? [duplicate]

just want to ask, I have a .tif file that contains all the elevation of a country. How can I convert that to a CSV file that contains x,y,z values where x and y are the latitude longitude respectively ...
0
votes
1answer
51 views

Terrain Accessibility map using GIS (ArcGIS or QGIS)

I need to make an accessibility map showing the walking distance based on the terrain and availability of road networks, could anyone point me in the right direction where i could learn to do so. ...
0
votes
0answers
20 views

QGIS export DTM with x.000 coordinates

I'm new at QGIS and would like to solve the following problem: I import points and breaklines and interpolate this data. Afterwards the generated DTM is exported to a new file (this works). Now I ...
0
votes
1answer
29 views

generate subcatchment starting from a DTM [duplicate]

I would like to know if there is a plug-in in Quantum GIS, which can help me to generate subcatchments starting from a DTM. Thank you very much!!!
0
votes
0answers
37 views

qgis - slope from DEM - errors due to projection and oversimplified 'z factor' [duplicate]

I'm trying to generate a slope raster from a DEM raster. It seems there is a pretty significant error due to the 'z-factor' option. I'm fairly new to this, but some other posts and responses ...
0
votes
0answers
70 views

determine the catchment area from dem or hillshade [duplicate]

I want to determine the catchment area of river from hillside. Is there a plugin that I can use in qgis ?
1
vote
2answers
148 views

How to calculate peaks in a DEM

How could I extract all peaks from a DEM (large mountainous area)? Peak means something like: a pixel which is sourrounded by other pixels with smaler elevation numbers in a area arround the ...
1
vote
1answer
60 views

What is the 'water retention capacity' tool and how is it used?

In the latest version of QGIS, I found a geoalgorithim in the processing toolbox that will generate 'water retention capacity.' I am familiar with DEM-based hydrologic modeling tools in QGIS, but I ...
2
votes
1answer
158 views

How do I run the nvis tool in QGIS GRASS?

I am trying to follow this workflow: [How to generate a DEM from a countour Shapefile?] and it's running fine, and when I hit view output or view results I end up with a flat raster with shading ...
3
votes
1answer
174 views

How to create DEM from contours without ArcGIS Spatial Analyst licence?

I'm trying to create a 3d DEM/DTM from a flat contour shapefile which has height data attached to each contour, but I'm not sure how to do this? I've found this post, on creating a dem from contours ...
6
votes
2answers
360 views

How to extract mountain peak points from a given digital elevation model?

For past couple of days, i m trying to determine how many mountain peaks are visible (line of sight) from a given location using POSTGIS. The data i have is DEM for Swiss and address locations from ...
2
votes
1answer
104 views

How to multiply raster DEM with a linear graph value

I would like to multiply my Raster DEM with a linear graph value y = mx + C. The graph values look as follows: I want to make a new raster where each cell will represent a damage factor from ...
3
votes
1answer
204 views

How to join 2D polylines and DEM into 3D polylines?

I got a simple question but could not find a satisfactory answer yet: I have a road network in 2D/PostGIS and a DEM. I want to turn the road network into 3D by retrieving the Z-value from the DEM. ...
2
votes
1answer
111 views

ASTER GDEM v2 coastline generation?

I try to generate world coastline 1:30000 from ASTER's DEM with: gdal_contour -a ELEVATION -fl 0 But above produce some of missing coastlines. Whats happening? Is it cliffy shore? How would you ...
0
votes
0answers
95 views

memory restrictions in QGIS Interpolate?

I am trying to make a DTM from contour lines (.SHP) using the Interpolate tool. The tool runs fine when I clip the data into smaller areas, but when running for larger areas, it crashes QGIS. Are ...
2
votes
0answers
85 views

Displaying DEM raster in QGIS

Using Raster>Analysis>DEM to display hillshade produces the message "gdaldem.exe had stopped working" so I asked the community. I'm new to QGIS, and I now realise after a little experimentation that I ...
3
votes
3answers
185 views

What DEMs does QGIS support? + DEM data sample

I am working on QGIS rasters. I want to know about DEM file formats supported by QGIS. I know that QGIS can read the GDAL supported formats. but what is GDAL supported format ? Does QGIS support the ...
0
votes
0answers
66 views

How to merge raster quadrangle tiles in qgis?

I've downloaded some dem tiles from here http://www.granit.unh.edu/data/search?dset=dem/dem174, which I'd like to merge into a single smooth digital elevation model usinq QGIS. So far I've tried ...
1
vote
1answer
140 views

Can I prevent QGIS raster clipper from changing output cell/pixel size?

I have performed a DEM extraction using the clipper tool in QGIS 1.9.0 Master, using a mask layer, the original resolution of the DEM is 20x20 but in the resultant DEM the new resolution is ...
0
votes
0answers
52 views

Adding elevation property to raster cells

I am trying to add elevation to raster cells. I have a land use raster map, and a DEM. And I'm at a loss to figure out how to combine them. Is it even possible to add "attribute" data like this to ...
0
votes
1answer
54 views

Qgis nightly build - DEM error

I installed Qgis 1.8 several months ago. It's been working like a charm. Earlier today, I decided to check out the latest nightly build. Installed GDAL 1.10 (already had 1.9 installed) and SQLite ...
0
votes
0answers
96 views

QGIS 1.8.0-Lisboa error message when converting DEM to Contours

I am trying to convert a small DEM (1 megabyte) into contours. When I go to - Extraction - Contour- and run it I get the following message: "ERROR 1: CPLRealloc(): Out of memory allocating 416 ...
3
votes
2answers
552 views

Is it possible to colour areas between (vector) contours?

...without making it a DEM first? Joshdoe seems to have done so ("Styled in QGis") here but doesn't say how. Thanks!
3
votes
3answers
850 views

Obtain all elevations points from a raster DEM

I need to obtain all elevation grid points from a raster DEM. I see the steps required as: Read in raster DEM (Arc Info Binary Grid format). Create subset area using Points2One (see triangle area ...
3
votes
2answers
1k views

How to generate a DEM from a contour Shapefile?

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, ...
0
votes
0answers
134 views

catchment delineation

I am trying to use qgis to delineate between three sub-sub-catchments. I have contour shape file of 20 meter height. Sub-catchment is about 12 square kilometers area but consist of three ...
0
votes
1answer
226 views

min and max values are not correctly calculated for DEM

I'm working with DEM in QGIS and need to know the min and max values of my data. In the Properties window, under the Metadata tab, the statistics section shows such values. However, I usually find ...
3
votes
1answer
321 views

Watershed extraction using different DEM tiles

I would like to extract the watersheds for a particular area using QGIS. However, I only have Aster 30m DEMs to work with, each tile covering one degree square. The problem is that I need to use ...
0
votes
0answers
97 views

gdal_merge.py aligns incorrectly at the seam of two GeoTiffs

I am trying to merge four GeoTiffs from the National Elevation Dataset (EPSG: 4269) into a 2x2 DEM using gdal_merge.py. For some reason, when it merges the upper two NED rasters, gdal produces a seam ...
4
votes
2answers
195 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
152 views

How to apply DEM elevation adjustment parameters?

I have a nice DEM, created from UAV data, which I want to process further in QGIS, my platform of first choice. In order to represent the evelation of each pixel correctly, I have to adjust the ...
1
vote
0answers
203 views

“topo to raster” tool

is there any analogue of "topo to raster" tool (ArcGIS) in QGIS? I need to creates surfaces from shp for some cases from points and for some from lines and this instrument is very convenient.
0
votes
0answers
31 views

How to extract elevation data from DEM along a polyline [duplicate]

I've been trying to use qGIS to extract and save as an attribute the data elevation along a line, knowing that something similar is available in ArcGIS using the Spatial Analysis tool. So far, ...
4
votes
2answers
537 views

How to drape a simple jpeg image over dem of some area?

How can we drape a simple jpeg image which doesnot have any geo referencing information over the digital elevation model in order to visualize it in 3D in QGIS?
3
votes
1answer
220 views

Hydro-Enforced/surface constraint DEM Creation using GRASS/QGIS

I am wondering if there is a way to create a hydro-breakline enforced DEM by means of any open source solution? I am able to create a DEM from Lidar data using GRASS, but would like to enforce some ...
3
votes
1answer
259 views

How to increase resolution of DEM rasters?

Thanks to the fine folks here at the GIS SE, I have managed to batch process a load of ASC files into raster hillshade TIFs. However, while they look fine on screen, when printed they are very ...
1
vote
2answers
129 views

Put color for raster data(aspect.tif) on QGIS1.8.0

I create aspect.tif from DEM file. I could put the values(0 to 360)from contrast enhancement. I could set color from color map(freakout or Pseudocolor). In here, the data is shown by only 4 colors. I ...
1
vote
1answer
116 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 ...
3
votes
5answers
1k views

Batch processing DEM rasters in QGIS/GDAL

I am attempting to add relief shading to map using .asc raster files, following this tutorial. It works well, but I have only tried it on single tile of raster data which is 20x20km. I want to ...
1
vote
2answers
519 views

Import Civil 3D DEM to ArcMap or QGIS

I have some survey data exported from Civil 3D in both dtm and dem formats. I thought the I would be able to use the dem more easily, but I think the format is different from a USGS DEM. Is it ...
6
votes
1answer
528 views

How to calculate te area between contour lines on a DEM with Qgis 1.8?

Does anyone know how to calculate the area in kmĀ² for each altitudinal band (between 100 and 200, 200 and 300...) based on a DEM? I added the contour lines with a distance of 100 metres but could not ...
2
votes
1answer
315 views

Orthogonal Height Profile along line (sextante -> v.segment, r.profile?)

While trying to find a way to find "valleys/ridges" within a DEM, I'd like to know if there are tools, plugins or "methods" known or available to automatically generate height profiles along a given ...
5
votes
1answer
146 views

Calc bottomline of valleys

Which way do I calculate bottomlines of valleys or even more preceise: which way do I "find" valleys (for example suggested tectonic faults). Sample below shows a height profile (profile from line) ...
5
votes
2answers
1k views

Exporting DEM-derived rasters to CSV from QGIS?

I have been able to import into QGIS a set of raster topographic maps and the associated DEM raster maps. It registered the two for me. From there I have calculated the associated slope raster map. ...
3
votes
1answer
68 views

Is it possible to create DEMs from ORT format in QGIS?

I recently requested DEMs for my area of interest. The data has however arrived in ORT file format - how do I create DEMs from this data in QGIS? When I open the files in Notepad there are three ...
8
votes
5answers
280 views

How to ensure uniform colour for DEMs?

This is a silly question, but one I've been trying to figure out for a while. I have two Aster DEM tiles, one next to the other. How do I ensure uniform colour for both?
1
vote
1answer
447 views

Problem merging two rasters in Qgis

I have two rasters in Geotiff, same CRS. I tried to merge them and I have this error code ERROR 4: `C:/Anita_Tepoztln/Rasters/e142.tif' does not exist in the file system, and is not recognised as a ...
21
votes
4answers
2k views

How to calculate terrain Curvature?

I have an elevation raster and I would like to get some basic terrain variables, such as slope, ruggedness, aspect or curvature. The problem is that I don't seem to have the possibility to calculate ...