Digital Elevation Model (DEM), which could be a Digital Terrain Model (DTM) or a Digital Surface Model (DSM).

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37
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7answers
35k 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 ...
24
votes
3answers
5k 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 ...
21
votes
6answers
7k 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 ...
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 ...
19
votes
2answers
2k views

Proper workflow for LAS to DEM conversion

I regularly come across LiDAR (.LAS) files with elevation data. When I do, I always struggle to find a way of converting them to a DEM for hydrological analysis. I have developed several workflows, ...
15
votes
11answers
23k 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
7answers
750 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 ...
13
votes
3answers
213 views

Account for bridge overpasses in a ground DEM to allow for water flow under the overpass

I have a bare earth DEM made from lidar data (A). It works well and has passed all accuracy tests. It is used in storm surge models. The problem we are having is on underpasses. I need to allow water ...
13
votes
2answers
1k 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: ...
13
votes
1answer
458 views

Creating nanoscale DEM with GDAL

A bit of a strange question perhaps, but let me give you a breif explanation of the background before my actual questions: Atomic force microscopy (AFM) is a method that, in short (and to my limited ...
12
votes
2answers
996 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 ...
12
votes
4answers
3k 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 ...
12
votes
5answers
8k 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 ...
12
votes
2answers
550 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 ...
11
votes
4answers
587 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 ...
11
votes
4answers
2k views

Comparing two Digital Elevation Models (DEMs) from LAS files?

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 want to compare how the Digital ...
11
votes
3answers
1k 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
520 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 ...
10
votes
2answers
1k 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
2answers
1k views

What software to use for making digital elevation models from UAV aerial imagery?

I have a an unmanned aerial vehicle (UAV, also called a drone) and would like to use it to create a digital elevation model and orthomosaic over a smaller area (10 km2). My platform will be able to ...
9
votes
4answers
3k 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 ...
9
votes
4answers
1k 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
3answers
3k 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. ...
9
votes
3answers
1k views

Create DEM from stereo pairs?

Does ArcGIS Desktop or any of its native extensions allow me to create DEMs from stereo pairs (acquired by satellite, GeoEye 1)? If the answer is a clear no, brownie points will go to an answer that ...
9
votes
2answers
709 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 the following datasets: 1) River cross section polylines ...
8
votes
4answers
4k 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
5answers
308 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
2answers
2k views

Workflow for determining stream gradient?

As far as data goes, I'm working with NHD .shp files, 10m DEMs, and some LIDAR data. My goal is to determine gradient for 100m segments of a network of streams. I'm already able to do this, but I ...
8
votes
5answers
648 views

How to calculate the total ascent along a path

I am working on a series of footpath routes and have been asked if it possible to calculate the total ascent that a walker would have climbed if the travelled along each route? I know that it is ...
8
votes
2answers
534 views

DEM Elevation Units

I'm fairly new to the GIS world, and have a quick question. I'm currently using 10.1. I do not know much about rasters, so does transforming a DEM from one projection to another automatically convert ...
8
votes
4answers
2k 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
605 views

Elevation profile sample point algorithm

In generating an elevation profile, samples from the underlying raster must be taken. If the objective is to create a profile of maximum quality, how should the locations of sample points be ...
8
votes
1answer
367 views

How to generate a DEM from isolines and spot heights?

I have two shape files containing height information of a certain area and I need to create a raster DEM with GRASS using them. file 1 consists of height information in contours (isolines) file 2 ...
8
votes
2answers
966 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
3answers
14k 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 ...
8
votes
1answer
153 views

River boundary (bank) extraction from LiDAR

Is there any way to extract a river boundary (bank) from LiDAR data and its products (DEM, intensity image and slope) automatically? Digitizing is very time consuming.
8
votes
3answers
473 views

How to extract breaklines from a given 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) - ...
8
votes
2answers
110 views

What is a good metric for mapping accuracy

I have recently received a dataset that supposedly mapped the altitude a given region (a DEM). I would like to determine the accuracy of the new map by comparing it with a previously generated DEM. ...
7
votes
2answers
2k 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' ...
7
votes
1answer
948 views

When to use IDW vs Kriging Interpolation for DEM creation?

I'm trying to create a DEM using point data spaced very regularly about 10m apart. The area I am interpolating is an educational facility with many flat parking lots and football fields but still has ...
7
votes
3answers
745 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
5answers
1k 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 ...
7
votes
3answers
327 views

How to get the subbasin area of each specified river segment?

I have a DEM file of one district, and I have used those following tools in spatial analyst tools in ArcGIS 10.1 to get files related to the original DEM file: Fill Flow direction Flow accumulation ...
7
votes
2answers
812 views

What is the smallest contour interval possible when derived from a DTM?

I am converting a 2m DTM to contours, and would like to have the smallest interval possible. Is there a theoretical limit, or even a rule of thumb for defining contour intervals based on the ...
7
votes
2answers
2k 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 ...
7
votes
1answer
887 views

Partially updating raster (DEM)?

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 Interpolation with Barriers. ...
7
votes
1answer
9k 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 ...
6
votes
3answers
5k views

How to use SRTM Global DEM for Slope calculation?

I have downloaded SRTM GDEM (~90 km resolution). I am using ArcGIS 10. I have tried to use spatial analyst to compute for slope. However, I can not compute for the slope. The output values has only ...
6
votes
2answers
101 views

Reducing elevation from DEM using ArcGIS for Desktop?

I am so curious how would I strip off elevation from the DEM. I don't know how I would explain it further but I have attached an image to clarify this. I wanted to eliminate the area shaded with ...
6
votes
1answer
4k views

Which is better, DEM or Triangles (TIN/Terrain)

Which is better DEM or TIN? What are the benefits/negatives of each?