Digital Elevation Model (DEM), which could be a Digital Terrain Model (DTM) or a Digital Surface Model (DSM).
26
votes
7answers
16k views
What is the difference between DEM, DSM and DTM?
I am listing some of the acronyms used in our work and had to stop to think about whether to list these together or separately. In some circles they are synonymous, in others they have distinct ...
17
votes
3answers
2k views
How to smooth a DEM?
I have a SRTM DEM and I want to create a shaded relief from it. I created the shaded relief in GRASS and the result is very nice, but a little rough becouse the area is near flat and the DEM is 90m in ...
14
votes
13answers
15k views
How to a convert LiDAR XYZ files to DEM / DSM?
Normally consultants (LiDAR survey) provide me with data to my specifications; already in ESRI GRID or ASCII GRID format. This way LiDAR data can be easily used with ArcGIS.
This time I only have xyz ...
13
votes
1answer
706 views
Good practice for generating contours from a DEM
We have just received a large set of DEMs at work and I would like to generate contours from them. The DEMs have a resolution of 1m and a size of 1kmx1km.
Output from gdalinfo:
Driver: ...
12
votes
4answers
2k views
What is the best colour-ramp to use for elevation?
This is maybe rather subjective as it concerns style, but I would like to have a few decent colour ramps for my DEM when it is layed over my hill-shading.
I have created the Swiss hillshade model as ...
11
votes
7answers
310 views
How to generate a random but believable digital elevation model?
Is there a way to generate a DEM, programatically or otherwise (arcpy or R?), that will feed into ArcGIS for further spatial analysis?
Perhaps this needs to be broken down into smaller incremental ...
11
votes
4answers
2k views
Shaded relief from DEM in GRASS and QGIS
I have been trying to get a good looking shaded relief model out of GRASS and Qgis for a day or so now and just can't seem to get it. The biggest problem I'm having is the valleys look like ...
11
votes
3answers
607 views
Detrending DEMs? - Removing the elevation trend over sloped surfaces (diagram included)
Is there a known methodology for removing the trend from a DEM surface?
For example, if I had a DEM of a river, that river would flow from high elevation (upstream) to lower elevations (downstream). ...
11
votes
1answer
328 views
QGis raster terrain analysis - The curvature filter puzzles me
I am a french Master student at university Grenoble INP, and during my master project I have worked on DEM (raster) terrain analysis. Thus, I have read the source code of several QGis-1.7.4 raster ...
11
votes
3answers
234 views
PostGIS interpolation / triangulation options
I'm looking for an open source workflow to automate DEM construction. We have a series of sites that fall within a LIDAR dataset. We want to create site specific DEM's for each site, and we're ...
10
votes
2answers
809 views
Surface distance on DEM between two coordinates
Given two coordinates on a digital elevation model (DEM), how do I compute the actual distance traveled between the two locations, assuming a straight line route? How will changing the resolution of ...
10
votes
4answers
362 views
Dikes extraction from DEM
I do have DEM of 1x1 meter and original LiDAR point cloud in .las, that DEM is made of. I need to extract river dikes (highest points of the dikes) to vector feature (point, polyline). Any idea for ...
9
votes
4answers
746 views
Are there any open source tools to detect and fill sinks on a DEM?
Are there any open source or inexpensive tools to detect and fill sinks on a DEM? ESRI Spatial Analyst is just out of my price range.
9
votes
4answers
888 views
comparing two DEMs
i have two Lidar las files, one is original let's say with X points. And the other is copy of the first las file but with Y points, where Y is less than X. Now, i wanted to compare how the Digital ...
8
votes
5answers
232 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?
8
votes
4answers
2k views
How to 'burn' a stream network into a DEM layer in ArcGIS 10?
I am working on a DEM that in an area where there is little relief. I would like to 'burn' the river network into the DEM so I can calculate flow accumulation and flow length accurately. I am using ...
8
votes
4answers
2k views
Code to calculate elevation profile along line from a DEM
Given a DEM (Digital Elevation Model) say in and a line (x1,y1) --> (x2,y2) (paired coordinates (x,y)), how can one calculate the elevation profile or cross-section projected on that line ?
I am ...
8
votes
3answers
930 views
Best method to aggregate 1m DEM mosaic to 10m DEM
I have a mosaic of a 1m LiDar derived DEM. I need to output a subset of the data as a 10m DEM. I am currently using the aggregate tool in ARCGIS 10 to produce a mean value for each new 10m pixel. ...
8
votes
4answers
1k views
How to aquire a topographical map of Britain?
First of all, let me say that I know next to nothing about GISs.
I'm trying to find / make / aquire a topographical map of britain. I want to use it as a height map in Dwarf Fortress so it needs to ...
8
votes
2answers
414 views
Extract the area of a DEM above where 60% of the region lies?
I have a DEM of a mountainous region. I'd like to extract the areas of the DEM above which 60% of the total DEM area lies. So, essentially I'd like to extract the areas representing upper portions of ...
8
votes
1answer
324 views
Floodplain generation given river section polylines, flood level elevation points and a DEM of the land surface
I am looking to generate flood plain polygons to represent 20 and 100 year flood zones, in the most accurate and efficient way possible given, given the following datasets:
1) River cross section ...
7
votes
2answers
449 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 ...
7
votes
3answers
439 views
Creating raster or vector raster from DEM point file?
i have a point shape of 75.000 elevation points in a regular 5 m grid.
We now want to create a polygon grid with the elevation points as "centroids".
Unfortunately, all attempts to do so fail:
I ...
7
votes
4answers
3k views
Is it possible to make a DEM from contours in QGIS?
Is it possible to make a DEM from contours in QGIS? I have a shp file (contours) and their heights, can I use QGIS for produce a DEM without using GRASS? I find this creating a dem from contours but ...
7
votes
1answer
538 views
Partially update a raster (a DEM)
My todays question is: How to update an .img DEM in ArcView 9.3?
I do have DEM which need to be updated only if few parts. The area to be updated has been produced in separate DEM with Spline ...
6
votes
5answers
757 views
Is there an online tile-based elevation service?
I am working on an application that requires the elevation at a given lat/long coordinate for lots of closely spaced coordinates along any given irregular path. (The path is a trace of a ...
6
votes
6answers
532 views
How can I convert a DEM into areas of “flatness”, with an arbitrary fill/cut to area ratio?
I want to find areas of relative "flatness" in a DEM.
How can I find flat areas? I want to find a neighbourhood of contiguous cells that have an elevation variance that is within a certain ...
6
votes
3answers
435 views
Generating a TIN from a DEM without ArcGIS
I'd like to generate a 3d terrain model moving from a DEM dataset (currently in shp and GeoTIFF format). As far as I understand it, the first step of the better path would be generating a TIN, but I ...
6
votes
3answers
530 views
What is a good way to produce wire frame images from DEM?
As part of a project for a wind turbine assessment, I would like to make a wire frame image to compliment my Viewshed / line of sight and Photo montage.
I have never created a wire frame image from ...
6
votes
1answer
480 views
FOSS method to split raster into smaller chunks
I have a raster (USGS DEM actually) and I need to split it up into smaller chunks like the image below shows. That was accomplished in ArcGIS 10.0 using the Split Raster tool. I would like a FOSS ...
6
votes
3answers
731 views
How to find the elevation differences between adjacent pixels in ArcGIS?
Is there a way to determine what the difference in elevation is between two adjacent pixels? I am using an SRTM DEM to map faults. I am using the vertical error (>16m) as a criterion for the ...
6
votes
2answers
1k views
How to change DEM's gradient colour?
I'm a newbie about GIS.
I'm from Italy and I've got a *.tif file of my region.
I've loaded it has raster but I have a question:
The dem has a gradient colour magenta.
How change this colour to ...
6
votes
1answer
509 views
Interpolation: irregular shape, merging DEM's
my problem is quite complex, though I hope that solution may be simple or at least possible.
I do have .img DEM 0.5x0.5m. DEM consists of river bed, river valley and adjacent areas (it is strip of ...
6
votes
1answer
332 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 km² 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 ...
6
votes
1answer
248 views
Problems creating TIN from British Columbia DEM data
Is anyone familiar with creating a TIN using ArcGIS9.3 and British Columbia DEM data (.GEN files)?
I can't figure out how to get the breaklines to work during the creation of the TIN. Using ...
6
votes
0answers
83 views
Automatic detection of breaklines with a DEM
Breaklines are very useful for describing a terrain - for example to build an exact TIN.
My question is, how to extract these breaklines from a given DEM.
I calculated the curvature (vertical) - ...
6
votes
1answer
333 views
How do I find least cost path over a DEM based on slope magnitude and direction?
What sort of algorithms can I use to find a least cost path through a DEM where it costs more to traverse a cell going downhill or uphill than it does to follow the contour of the land?
All the ...
5
votes
2answers
879 views
How to build an artificial 'dam' across a river?
I have a DEM.
Created all files related to watershed including accumulation, direction, streams etc...
I'm stuck creating a dam.
I request you to please let me know how to build an artificial 'dam' ...
5
votes
2answers
860 views
Is there a way to clip a raster using a vector polygon without having Spatial Analyst?
I have ArcView 10 and I'm trying to clip a DEM (TIFF) to a wilderness boundary (polygon). I know ArcView won't let me do this without Spatial Analyst, but I don't have $2500.
I tried exporting my ...
5
votes
1answer
2k views
Which is better, DEM or Triangles (TIN/Terrain)
Which is better DEM or TIN?
What are the benefits/negatives of each?
5
votes
2answers
453 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
3answers
84 views
How to transform GPX-tracks into elevation-tracks with any GIS?
I have a GPS track in GPX format available from a recent bike tour and I need and want to do some analysis on the tracks. I'm wondering whether there is any way to transform the GPX data into an ...
5
votes
3answers
5k views
How to extract raster DEM elevations to vector attribute tables in ArcGIS 10?
I have an ArcMap 10 project with multiple layer groups. One layer is a raster DEM, another layer group is a bunch of vector shapefiles (including points, lines and polygons). The client wants all ...
5
votes
1answer
4k views
How to calculate an elevation profile for a polyline in arcgis 10 with spatial analyst/3D analyst?
My elevation data is a floating point tif. I have a road for which I need to calculate the elevation profile, but I can´t see the tools to do this.
Can I do this with ArcGIS?
yours,
Rob
5
votes
2answers
767 views
Can shaded relief be “blended” with DEM colour ramp in ArcGIS to produce a more visually dramatic result?
Not being able to use true transparencies with ArcGIS colour ramps where only solid colours are allowed has me always wondering about how to improve the look of the surface in my maps without ...
5
votes
1answer
105 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
227 views
Problem Visualizing 3D Terrain Model - USGS DEM
I recently downloaded a GeoTIFF 1 arc second from the USGS National Map Viewer. I added the raster to ArcScene and attempted to visualize the data in 3D. I set the Base Height to Floating on a ...
5
votes
1answer
206 views
How do I get the upstream distance to all points in a DEM from a single downstream point?
I want to get the upstream distance to all points in a DEM from a single downstream point. The goal is to create a "downstream distance to a point grid". This then would allow me to create "distance" ...
5
votes
1answer
5k views
creating a dem from contours
I have a large set of contours that I received broken down into several different subsets. I have merged most of the subsets together creating a larger set of contours in three different files. I have ...
5
votes
1answer
4k views
Watershed Delineation
I am trying to delineate just the catchment area of some lakes, and am wondering the correct way to do this. I already have a filled DEM, along with a flow direction and a flow accumulation raster. Is ...
