Digital Elevation Model (DEM), which could be a Digital Terrain Model (DTM) or a Digital Surface Model (DSM).
3
votes
3answers
2k views
Global DEM to 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 ...
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 ...
5
votes
2answers
873 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' ...
1
vote
1answer
133 views
Calculating mean upslope aspect
I am trying to write a python script to calculate the mean aspect upslope from each cell in a DEM. I have the general workflow down, but my final output is restricted to angles between 0 and 90 ...
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 ...
2
votes
2answers
2k views
Viewing .las format LIDAR data in QGIS?
Is there an easy path to visualizing this LIDAR data? I have QGIS, and some USGS LIDAR data in (.las) format downloaded from http://lidar.cr.usgs.gov/ . This means I have both the (.las) and ...
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 ...
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 ...
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 ...
6
votes
1answer
330 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 ...
4
votes
2answers
710 views
Translating grid to USGS .dem in C# via GDAL
I am attempting to translate ArcInfo binary grids to USGS DEM format (.dem). I have installed the GDAL .NET bindings thru this build installer. I can get to GDAL in my C# add-in I am working on. ...
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 ...
5
votes
2answers
765 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 ...
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 ...
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 ...
4
votes
4answers
713 views
Definitive source for downloading DEM data
USGS has been moving towards serving data through The National Map Viewer. They have several WMServices through their website that serve elevation data to the public (hillshade & DEM). The ...
3
votes
4answers
392 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 ...
3
votes
4answers
2k views
Can I convert ESRI Grid (DEM) raster to USGS DEM?
There is a tool for DEM to Raster in ArcGIS but I need to convert my ArcGIS DEM rasters (mostly LiDAR) into USGS DEM. The idea is to import this DEM into Sketchup and create a "sandbox" TIN surface ...
3
votes
6answers
1k views
shadow simulation from buildings
is it possible to use hillshade function in ArcMap to calculate shadow areas of buildings or simulate shadows of buildings, using DSM of the buildings and the sun angle and azimuth?
2
votes
1answer
71 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 ...
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 ...
7
votes
2answers
447 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
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 ...
5
votes
2answers
856 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
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
3answers
599 views
getting from a DEM to points that could be used for a TIN
I have a DEM, and would like to create a set of points that I can use to make a mesh for a 3d modeling program, such as Maya, Blender, or SketchUp. If I were to make a TIN from a DEM in ArcGIS, ArcGIS ...
4
votes
1answer
345 views
Is it possible to reverse the trend/values of a raster?
For example - if I have a raster DEM covering a stream with higher elevations in the west (up river) and lower elevations in the east (down river) is it possible to reverse this trend so that the east ...
4
votes
1answer
290 views
When merging two DEMs, do they have to be in the same pixel bits?
I have a simple question. I have 2 different Digital Elevation Modeling (DEM). One is the state DEM and has 30m and has 16 pixel bit. I have a couple of smaller DEM that has 30m but they have 32 pixel ...
3
votes
2answers
286 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. ...
2
votes
4answers
292 views
Is there a way to programatically force RGB (3 bands) in a raster with arcpy?
I'd like to include conversion to a 3 band RGB raster in a script to prepare multiple DEMs for image processing. The input files are rasters extracted from a raster mosaic.
The manual option is to ...
2
votes
2answers
457 views
1'' DHM: Hillshade is too rough - how to “generalize”?
I got that hillshade from my DHM (I used the hillshade-module from qgis). For my purpose there a too much relief details (roughness). How can I get rid of them in QGIS or GRASS?
Thanks!
Martin
