Hi Tenzing,

If you have stereo pair of satellite images or overlapping aerial photographs or even UAV acquired imagery, you can use a standard GIS software to generate a DEM based on the principles of Photogrammetry. There are open source as well as commercially available softwares which can do the job. ERDAS Imagine LPS Suite, ENVI, ArcGIS, PCI Geomatica, NASA's Ames Stereo Pipeline, Pix4D, Drone2Map, etc. are some of the names in the business. The internet has made our lives much easier nowadays. It might be a good idea to google for 'dem generation with stereo' and you will get thousands of results.

Hope this gives you some hint. 

http://www.crisp.nus.edu.sg/~research/dem/dem.htm

https://ti.arc.nasa.gov/tech/asr/groups/intelligent-robotics/ngt/stereo/

https://www.youtube.com/watch?v=rDnWYh36d3c

https://www.youtube.com/watch?v=WoTZj77F08M

https://www.orfeo-toolbox.org/

Thank you very much James Varghese, it was very much helpful.

PL FALLOW THE ADVISE OF James Varghese

There is a great free tool from IGN in France - MicMac. It allows you to generate DEM from all kind of source images. One of the great points is that it allows to generate DEM from uncalibrated cameras, e.g. from a UAV flight. have a look into http://logiciels.ign.fr/?Telechargement,20

Hope this helps,

Uwe

Dear Tenzing:

As our colleagues stated, you need a stereo or overlapping images (satellite or aerial) to determine your DEMs. Regardless of what software you are going to use, we follow the following steps:

1. You need to measure conjugate points in two images or more. The measurement of the conjugate points can be done manually or automatically through image matching.

2. Then you need some control points in the ground. Their number depends on your mathematical model that establishes the relationship between the image and the ground. Control points are conjugate points in two images or more with known ground coordinates.

3. You need to solve a problem of 3D geo-referencing of each image. In photogrammetry, this process is called the Exterior Orientation Problem (EOP). In the solution of the EOP you need the ground control points mentioned in the previous step.

4. Then you need to solve an intersection problem to determine the XYZ for the conjugate points that do not have ground control points. These XYZs are your DEMs.

Regards,

Gamal

Thank you very much Uwe Bacher and Gamal Seedahmed, your suggestions were more than helpful.

The DEM Extraction Module requires a separate license.

A digital elevation model (DEM) is a regularly spaced raster grid of elevation values of a surface terrain. You can use DEMs to produce maps such as contour maps, orthophoto maps, and perspective maps. You can also use DEMS for route planning in the construction of highways and railways. In remote sensing, DEMs are used in mapping, orthorectification, and land classification.

The DEM Extraction Module enables you to extract elevation data from scanned or digital aerial photographs, or from an along track or an across track pushbroom satellite acquisition, such as those from the ALOS PRISM, ASTER, CARTOSAT-1, FORMOSAT-2, GeoEye-1, IKONOS, KOMPSAT-2, OrbView-3, QuickBird, RapidEye, SPOT, WorldView-1, WorldView-2, or Ziyuan-3A satellites. Along track stereo images are acquired on the same orbital pass by a satellite which usually has more than one sensor looking at the Earth from different angles. Across track stereo images are those taken by the same sensor on multiple orbits.

The DEM Extraction Module also supports Digital Point Positioning Data Base (DPPDB) data.

The DEM extraction process requires a stereo pair of images containing rational polynomial coefficients (RPC) positioning from aerial photography or pushbroom sensors. RPCs are used to generate tie points and to calculate the stereo image pair relationship. DEM extraction does not currently support replacement sensor model (RSM) positioning.

The DEM Extraction Module is comprised of DEM Extraction Wizard and three DEM

tools: DEM Editing Tool, Stereo Pair 3D Measurement Tool, and Epipolar 3D Cursor Tool.

You will find below a summary of key functionalities of DEM Extraction module associated with ENVI software.

- DEM extraction is a multi-step, decision-making process that involves setting numerous parameters. You can run the steps individually from the Toolbox, or from within the DEM Extraction Wizard. The Wizard guides you through nine steps. It presents you with objective parameters, such as minimum/maximum elevation of the area of interest, as well as other strategy parameters that depend upon the terrain relief, cultural content, image quality, shadowing, and the desired speed of operation.

As with the DEM Extraction Wizard, you can extract a relative or absolute DEM from a stereo pair of images using the Stereo Pair 3D Measurement Tool and Epipolar 3D Cursor Tool.

- The Stereo Pair 3D Measurement Tool allows you to select a common point from two stereo images and calculate an elevation value for that point (see The Stereo Pair 3D Measurement Tool for information about this tool).

- The Epipolar 3D Cursor tool allows you to perform 3D measurements in a 3D stereo viewing environment based on an existing epipolar stereo pair of images. You can view an anaglyph of epipolar images and adjust the apparent height of the cursor to extract elevation data (see The Epipolar 3D Cursor Tool for information about this tool).

I download ASTER image 3N and 3B and I try to extract DEM with high resolution. I try it in ENVI software but I have problem i don't have RPCs file which is important to the extraction. if there is a way to help me to extract DEM and how i can make it best DEM. best regards 

Agisoft Photoscan might help!

Toposheets?? How do i filter out contour lines from scanned toposheets tiff image.?

or

with Landsat 1-5 iamgery

You can use ARC GIS software there have a tool, arc hydrology you can process data

Why do you need to create a DEM ?

For most of applications, one can use SRTM and ASTER DEM data which have 30 m resolution and are freely downloadable.

Regards

Freely available dem can download from earth explorer and you can create dem from google earth and stereo pair satellite images.

You can use Sentinel data to generate DEM and ALOS PALSAR DEM is also freely available.