For questions about Digital Elevation Models (DEM), Digital Terrain Models (DTM) and Digital Surface Models (DSM)

learn more… | top users | synonyms (2)

3
votes
1answer
52 views

Scripts to automate conversion from DEM to contour shape files

I am using the DEM files in the Cornell CUGIR repository to build contour layers in QGIS. The problem I have is that while it is easy to do, it requires many manual steps in QGIS that are both ...
1
vote
1answer
43 views

Hillshade effect not working when no data is on screen

I'm working on a DEM and I selected hillshade effect to be active. The problem is that I can't get it to appear when a no-data area is shown on my screen. If I move the area just enough for the no-...
4
votes
1answer
40 views

Grid size of a Digital Elevation Model developed from topographic surveyed elevation contour line?

I have generated a Digital Elevation Model from elevation contour line. I got these elevation contour line at 20 cm interval from DGPS survey. What would be the grid size of generated DEM in "m". ...
2
votes
0answers
37 views

Watershed delineation with meandering river

I'm using ArcGIS (Hydrology toolbox) for watershed delineation for a number of pour points, and I'm running into problems with very meandering rivers on extremely flat alluvial land (Amazon basin). ...
1
vote
0answers
45 views

SAGA GIS Channel network crash

So, i had this very weird bug while treating my dem data lately. I used SAGA to create flows channel networks on a dem i acquired a little while ago. Preprocessed it using sink route detection and ...
2
votes
1answer
29 views

contour lines/ basement contour extraction

My purpose: getting out area between elevation contours (like b/w 600m and 700m). The contours could either be elevation ones or the basement contours. I got elevation contours using spatial analyst ...
1
vote
1answer
47 views

How to do diagram block with open source software?

I would like to do a block diagram (topographic and geological representation). Is it possible to do this with QGIS (or other open source software), in Windows 7?
2
votes
1answer
36 views

How to calculate the right area in polygons with help of DEM?

I have used infra red photos to identify territories in Norway where I have drawn polygons for different vegetation. I wonder if there is a way to use the polygons with elevation data to get the exact ...
1
vote
1answer
35 views

5x5 raster filter in ArcGIS?

Normally, I am using the 3x3 lowpass filter if I need to filter a DEM. However in one case, for better results in curvature calculations, I would like to do a 5x5 filtering. How is this possible in ...
3
votes
1answer
36 views

Do outputs (shp, dwg) inherit vertical datum from input (las) files?

I'm working in ArcMap. I pulled LiDAR data off earth explorer and created a DEM with the LiDAR data. I then created contours as a SHP file and exported to DWG (CAD). I was asked if the CAD file's ...
3
votes
1answer
60 views

Reading 1/3 arcsecond DEM data using C++?

I am writing my own application to use and present elevation data. So far, I've been easily using the three arc second SRTM data presented in ArcInfo ASCII format. But now I'm looking to use the ...
1
vote
1answer
2k views

Creating Cost Surface Raster for Least Cost Path Analysis?

I have a DEM raster and would like to carry out a cost path analysis. Among other factors such as slope, proximity rivers etc. I would also like to take elevation into consideration. According to ...
0
votes
0answers
35 views

Is it valid to resample a raster from 1m to 3 feet?

I know that in general it is not a good idea to up-sample. I am curious if it would still be be a "bad idea" with a minor change like this from 1m resolution to 3 feet? Going to 3 feet would not ...
0
votes
1answer
53 views

Get Elevation of XY points [duplicate]

I am working with ArcMap 10.3. I have imported DEM files. When I imported the files they had the extension of .DDF. I would now like to be able to take a list of XY coordinates and, for lack of a ...
1
vote
1answer
59 views

How to speed up raster2pgsql?

I'm trying to upload a 37 GB raster dataset to PostGIS. The raster is out-of-db (-R option), so the actual pixel values are not stored in PostGIS. I'm using this command: raster2pgsql -s 25833 -C -I ...
1
vote
2answers
78 views

programmatic DEM downloads similar to landsat-util

I recently discovered landsat-util, and was wondering if there was an equivalent command-line application for global elevation data, (for data around 1 arcsecond resolution, preferably geotiff) or if ...
7
votes
2answers
14k views

Download new SRTM 30 meters

I read about the new version of the digital elevation model at 30 meters (SRTM 30 meters), but I can not find from were I can download it. some sources: http://glcfapp.glcf.umd.edu:8080/esdi/index....
2
votes
0answers
26 views

Does USGS 3DEP data use a hash or checksum?

I'm downloading some USGS 3DEP elevation data, e.g., the file at the following URL: https://www.sciencebase.gov/catalog/item/563afea8e4b0d6133fe7357b The "ID" of this file is given in both the URL ...
0
votes
1answer
30 views

Seeking low-resolution DEM of California?

I'm trying to create a 3D model of California (which I'll manipulate in Blender) at a fairly low resolution — just enough for large features (like Mt. Tamalpais, Coronado, etc.) to be legible. ...
0
votes
0answers
20 views

generating DEM from many files with .asc extension for each cell

I am the beginner of arcswat and have a problem in the first step of setup. I have recieved a folder of DEM which is contain many files with .asc extension each representing one cell when I add them ...
2
votes
1answer
130 views

How to remove las2dem streaks from raster DEM?

I've created a series of DEM files using the las2dem tool from LAStools; however since I don't have a licensed version they have black streaks running across them. Does anyone know a good method for ...
0
votes
0answers
36 views

SRTM data to 7.5 min DEM or 1-deg DEM

I have an issue. I have SRTM data from here (http://www.webgis.com/srtm3.html) which is approximately 90 m / 3 arc-second. I want to convert it to 7.5' DEM or 1-deg DEM. Is it possible? Or is there ...
1
vote
0answers
22 views

Zonal smoothing on a specified area of a raster?

Is there any way to smooth a specify an area on a raster, such as a DEM, and smooth it? For example, I'd like to smooth out the artifact highlighted in the red box. What is the best course of ...
4
votes
3answers
157 views

What is the difference between DEM data sources?

I have started experimenting creating basic 3D elevation models in QGIS recently. It turned out for me that there are several free sources of DEMs, like USGS's EarthExplorer, CGIAR-CSI's Digital ...
1
vote
2answers
56 views

How to get the z values from a DEM?

I have to get to know the approximate amount of volume of rocks in one area. For that, I need the elevation information to see where slopes or inclinations are located. I downloaded from the USGS ...
1
vote
0answers
25 views

Ideal minimal area for watershed automatic delineation using DEM SRTM

I need to do a bunch of analysis on a city using for that, watersheds . As smaller the watersheds are, better are quality of my work. Due to the vertical accuracy of SRTM DEM, I know there are some ...
0
votes
0answers
61 views

Creating a Greyscale DEM from Multiband (RGB) GeoTIFF in QGIS

I'm trying to merge some river bathymetry with LiDAR from the surrounding riverbed using QGIS 2.14.0 Essen. The river bathymetric data is a GeoTIFF, and it comes with a separate scale associating the ...
3
votes
1answer
500 views

converting vectors to raster (burning streams)

I converted my stream vector to a raster file (using polyline to raster conversion tool). I anticipated that I would get a No Data row in the raster file attribute table, so that I could use a ...
1
vote
1answer
291 views

Creating DEM from cross sections in ArcMap?

I have a DEM in arcmap and cross section of a river which flows on the Dem in Hecras. I now the cross sections are more accurate. I want to make a DEM from some of my cross sections and stitch it on ...
1
vote
1answer
39 views

How to edit a DEM in ArcMap

I want to take a DEM and edit it using a tool in ArcMap where it will take all the areas above a certain elevation and lower them all to the elevation I choose. For example, I would want everything ...
2
votes
3answers
1k views

Advantage of Digital Elevation Model (DEM) in Agriculture?

I have given the task to create Digital Elevation Model (DEM)'s of an agricultural area. I am programmer with Computer Science background and very new to GIS can anyone explain what is advantage of ...
0
votes
1answer
57 views

Obtain free DEM data of South China

Is there any free source of Digital elevation model of China with the resolution of 30 meters or better and vertical accuracy of +-5m. Something along those lines
0
votes
1answer
68 views

How to calculate and compare RMSE between DEM using different interpolation methods?

I have data from aerial photo, it was built from stereo photo so I have 3D information that I am using for the DEM. I extracted it into shapefile. I want to get RMSE (Root Mean Square Error) from ...
2
votes
1answer
30 views
2
votes
1answer
1k views

Getting Negative Topographic Wetness Index (TWI) values in SAGA GIS?

I am getting negative topographic index wetness values in SAGA GIS - anyone else every get this? Not all negative values, but the minimum of the TWI range is negative for some steep watersheds we are ...
1
vote
3answers
362 views

Open LiDAR DEM of the UK with *.asc extension

I've downloaded a tile of a freely accessible LiDAR DEM of the UK from http://environment.data.gov.uk/ds/survey#/download. But I don't know how to open it. The files inside have the *.asc extension. ...
6
votes
3answers
5k views

How to create contour lines from point data using QGIS?

I'm using QGIS 2.4.0 and I have a shapefile of points with elevation data and X and Y coordinates. I'm using windows 7 OS. The idea is to create a contour line SHP using my point data. My question ...
0
votes
1answer
48 views

Removing every second row and column cells from a raster file

I have a SRTM 3 arc second topography model (.tif file). If I remove every second row and column of cells from the grid, can it be said that the model becomes a 6 arc second? Or does SRTM 3 arc ...
0
votes
1answer
316 views

gdalbuildvrt error when mosaicking SRTM data with different NoData values

I'm attempting to mosaic together 9 SRTM tiles downloaded from CGIAR to produce a DEM of Borneo. I'm using: gdalbuildvrt Borneo.vrt BorneoSRTM/*.tif where BorneoSRTM contains the 9 tif files to be ...
1
vote
0answers
71 views

DEM / Basemap Alignment

The image below shows the problem I'm facing. I'm trying to align a DEM with the ArcMap Imagery Basemap. Unfortunately, I can't make them to perfectly align. I tried changing the coordinate system to ...
2
votes
1answer
851 views

Converting LAS file to .asc DSM? [duplicate]

I want to count trees in SAGA GIS and I am trying to follow the steps described in Counting trees using segmentation and vectorization in SAGA Gis from dominoc925.blogspot.com (05th, March, 2012). ...
1
vote
1answer
54 views

Creating DEM from point data in CSV files using QGIS?

how can we create a DEM in QGIS from point data in CSV files? A similar problem was discussed here, using a shp-file. Our CSV's are too big, so that dxf2shp crashes. So we are looking for another way ...
4
votes
1answer
3k views

How can I create a DEM from Point Data?

my boss gave me a small 3D-point-shape-file and asked me to make an DEM from it, wich I should put together with an older DEM of the same site, wich was made with Surfer. I created a raster-layer ...
0
votes
2answers
341 views

r.topidx error: required parameter output not set

I'm calling GRASS r.topidx from QGIS 2.2.0. I can get other tools to work on the DTM, for example r.watershed. But r.topidx I get the Oops message: Oooops! The following output layers could not be ...
3
votes
1answer
52 views

Change direction of polylines from DEM data

I am trying to define the direction of my polylines (which represent gutters in a drainage system). Does anyone know if it is possible to define the direction based on elevation data extracted from a ...
1
vote
0answers
28 views

Individual tree extraction [duplicate]

I would like to extract individual trees in ArcMap 10.1. I have 1.3 meter resolution DSM data created from aerial images. I used Crown Height Model to extract tree heights (as attached file), but I am ...
1
vote
3answers
200 views

Converting DEM text file to tiff file in QGIS?

I am trying to convert a digital elevation model in txt file format to a raster file (tiff) with qgis. The file format is *.dat. The coordinate system is Gauss Krüger, Bessel, 5. meridian. First I ...
2
votes
1answer
48 views

How to import a digital elevation model in Germany Gauss Krüger from .dat file?

i am very new to qgis. I want to create a hillshade file and also calculate the inclination. The structure of the digital elevation model data looks like this: 5390.0125 5659.9875 251.8 5390.0125 ...
2
votes
1answer
173 views

Filtering noise out from bare-earth DEM with terrace fields?

I have a 1m bare-earth DEM, derived from LiDAR data, representing a terraced landscape. For the sake of any subsequent use of the DEM (e.g., least-cost path, cost surface analysis, and the like) I am ...
1
vote
1answer
52 views

Convert dem and geotiff to collada model with texture

I have a digital elevation model (dem) file with corresponding orthophoto in geotiff format. What I need to do is to create a 3D model of the terrain with textures (preferably in collada file). I ...