[Qgis-user] Merging DEMs

[Zoltan Szecsei]

On 2014/05/29 15:25, Randal Hale wrote:
> I have two Digital Elevation Models - Imagine a square cut into two 
> equal triangles.
>
> No matter how I do it - One DEM overwrites the other one so I'm only 
> ever getting half of the elevation model I want when I merge them. It 
> appears GDAL only takes the last Elevation model and uses that to 
> overwrite the First. I've tried making no-data transparent....I've 
> converted the img to a tif (these are 1/9 DEMs from the USGS National 
> Map). In someone's infinite wisdom they were cut at the North 
> Carolina/South Carolina State Line.
>
> Thoughts or ideas?
>
> Randy
>

Sounds a bit like "the other triangle" is filled with null type values?
Try looking at them as points in QGIS or something to see if the blank 
halves actually carry data which is overwriting the other half when you 
merge them.
I have no experience using USGS DEMs (btw :-) )

HTH
Zoltan

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Geograph (Pty) Ltd.
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