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I am very new to Quantum GIS, I want to create a digital elevation map a particular region, I would very much appreciate if some one gives me a step by step procedure.

Thank you

edit by Martin: I have the same question, but I want to create DEM from scan map (the territory of interest is aprox. 28 square km). Work flow: First open the map in an image editor (GIMP), select by colors with some tolerance and select the black color. Invert selection and delete non-black stuff. Save as Tiff WITH NO COMPRESSION. And then what is next step in QGIS with Grass Plugin? How can I get the contour values to the Tiff (my big problem)? After all is no problem make DEM from contours, I guess. Sorry for this "stupid" questions and thanks for all your replyings. Regards Martin

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Do you have some sort of base elevation data that you are going to use as the basis of your DEM? –  Get Spatial Jun 18 '12 at 14:55
    
which 'particular' region? –  Mapperz Jun 18 '12 at 15:30
    
What is the size of this region? –  MappingTomorrow Jun 18 '12 at 15:40
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Some existing threads may give you a quick start, jetson, which would allow you to re-focus this (otherwise broad) question on whatever obstacles you may be encountering. –  whuber Jun 18 '12 at 16:30

2 Answers 2

there are lots of information about creating dem. but you must be clear about what data you have?

  1. Creating a DEM from contours, here
  2. Creating a DEM from vector data, here
  3. Creating Maps from SRTM Data, here
  4. Inverse Distance Weighting (IDW) Interpolation using QGIS , here
  5. A workflow for creating beautiful relief shaded dems using GDAL, here

dem

i hope it helps you...

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A DEM either constitutes or requires a data input, it's not something the GIS can create itself. QGIS needs some indication of where the ground is. That data may be created via a ground survey effort, an aerial LIDAR scan, photogrammetric interpolation, or through a plane or satellite-based synthetic aperture radar. There are workflows that may incorporate GIS software to modify these datasets, but we'd really need to know where the data is coming from to help there.

The two big semi-global DEMs out there are the Shuttle Radar Topography Mission (SRTM):

http://www.cgiar-csi.org/data/elevation/item/45-srtm-90m-digital-elevation-database-v41

and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER):

http://asterweb.jpl.nasa.gov/gdem.asp

There's also the upcoming TANDEM-X product:

http://www.dlr.de/hr/desktopdefault.aspx/tabid-2317/3669_read-5488/

These are relatively raw data products, with some holes and artifacts. SRTM, at least, has been around quite a while now, and has been smoothed out and refined into national-scale production-ready data products by a number of organizations. The National Elevation Dataset is the official US DEM:

http://ned.usgs.gov/

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-1 - A DEM can be both an input and an output. The input could be from a source you stated. An example output would be: You have an area surveyed. The surveyor provides you with elevation contours in CAD format. You then convert these to a DEM using the "Grid" command in QGIS, for the purpose of performing different types of analysis. –  Get Spatial Jun 18 '12 at 16:11
    
The point is that a DEM can't be created without some sort of input, external to the GIS program. –  MappingTomorrow Jun 18 '12 at 16:23

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