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Guest AndrewMcGregor

SRTM exact ???

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Hi all,i just have the same problem, as day's before. I've downloaded the 90m .hgt SRTM data files of my area Hamburg / Germany.As i load the data in the FSDEM program, i like to cry. Is it real? Is it exact? The answer is: NO !!!What you see in the picture below, is an image of the FSDEM program, display's the area near Hamburg.http://mitglied.lycos.de/chatpinforyou/srtm/coustline.jpgThe redline display's the REAL coustline of the Elbe river. At the east site of the map is the city of Hamburg, left of the picture, at the right site, the Elbe river go into the northsea. But the SRTM data don't show the scenery as is it is. SRTM data show's me a value of -7 meters in the north of the Elbe river coastline. This is realy trash. At this region we have no landscape at -0 meters MSL.So, for this time, before i resample the data, i have to rework the SRTM data and try to find a program that can do this.So, is there anyone out there, know's a program that !!! EDIT !!! SRTM data? Or, is there a program that can interpolate the area with another dataset?Thanks in front for your help, i'm sorry about my bad englishOlli

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Well, I do most of my mesh creation using MWGraphics for SRTM 3" and SRTM30. on the other DEM types I use another tools to do the conversions.Of the programs you can use to check or modify your SRTM data, Blackart, MicroDEM and Global Mapper can help you refine your editing.What I've done is load the SRTM into a MWGraphics project and in paralel load it into Global Mapper. I have edited a shader there using the same color scheme of MWGraphics. Global Mapper 6 lets you zoom to 1:1 projection, meaning that if you see a pixel in the window, it keeps being a pixel in the DEM. Then I move the DEM graphic and do screenshots to cover the entire degree block, fit them in a single image and use it instead of the one generated by MWGraphics. Then I use the adjust tool to conform the terrain to a realistic altitude and soften the water edges.Hope that as a hint it had been valuable.

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SRTM tiles are often offset a little bit in altitude, and there are other oddities.Remember too, SRTM is relative to WGS84, not mean sea level, which is often several meters different. So, your sea level is 7m or more below WHD84 reference? Add 7m (or whatever it turns out to be) to the whole tile.

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