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I am wondering if I could merge DEM and Hillshade ? What is the pro and cons for that? Thanks

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possible duplicate: gis.stackexchange.com/questions/19386/… –  Jakub Oct 17 '12 at 19:59
    
For now I don't have the ArcGIS 10 –  PROBERT Oct 17 '12 at 20:12
    
I removed all the ArcGIS tags to reflect the lack of ArcGIS software to carry out a solution and to keep this from being a duplicate of the previous ArcGIS-oriented question. –  whuber Oct 17 '12 at 21:15
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What end-product do you hope to produce? After all, hillshades are derived from DEMs. –  Aaron Oct 17 '12 at 21:27
    
Listen all, I got my ArcGIS 10 upgrade. Finally and I was able to perform Elevation and Hillshade just exactly what I wanted ! I created one Desert tint hillshade ! Thanks. –  PROBERT Nov 7 '12 at 22:01
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3 Answers

up vote 3 down vote accepted

Combined pan-sharpening, contrast stretching, and gamma stretching functions

If you have access to ArcGIS (and the Spatial Analyst Extension) you can use the technique described in this blog to "blend" DEM (or imagery) with shaded relief. The main disadvantage of this solution is that it is static; you need to produce an RGB raster from your DEM so if you need to change the original symbology in any way you have to do it on the original DEM raster then re-do the RGB raster and repeat all the steps. Luckily 95% of my current work is in the same geographical area so I just built various models and schemas that suit the various scales I often use and simply copy and paste them in the map as needed. As for using this approach with imagery; one unexpected advantage beyond just the wow factor is that field crews and environmental scientists like that use these "imagery-hill-shade blend" maps to get a sense of the terrain characteristics as well as the aerial perspective in one glance.

As a side note; It does require a certain amount of tinkering around with the functions to get the look of the resulting layer just right.

Below is an example and the input rasters. The last image is an example of imagery "blended" with DEM. No transparency was applied, the below examples are a result of the above mentioned functions as described in the linked ArcGIS Resource Centre blog by rajnagi.

DEM & Hillshade:

enter image description here

Input DEM:

enter image description here

Input Hillshade:

enter image description here

Imagery & Hillshade example:

enter image description here

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Thanks for the info. I don't know if this will work with 9.3.1. I don't have the 10 yet. –  PROBERT Oct 18 '12 at 14:45
    
I think it might. –  Jakub Oct 18 '12 at 17:37
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You could 'merge' dem and hillshade. You could add 1 (grayscale or colormap) or 3 (rgb) bands to the dem. I don't see any benefit to doing so, and it would probably cause confusion given 2 band images are rare and 4 band images will likely at some point be misinterpreted as and RGBA image. Personally, I wouldn't do it.

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How do I do that ? Do you mean the grayscale or bands from the Landsat ? –  PROBERT Oct 17 '12 at 19:14
    
My thinking is to export each DEM and Hillshade and then merge both is that what you meant ? –  PROBERT Oct 17 '12 at 19:47
    
Sorry, I may have misunderstood. Where does landsat come it? Some hillshades can be colored as in the example below, that is where 3 bands come in. DEMs are usually a single band with z values. –  kyle Oct 18 '12 at 16:23
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In ArcGIS you can apply a hillshade effect to a DEM - it's a check box on the Symbology tab under Properties.

enter image description here

This will allow you to keep the values in the DEM, but still allow for the visual effect of the hillshade.

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