Take the 2-minute tour ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

I downloaded a selected sub-set of the USGS National Elevation Data (NED) using their online GUI. This download came in the form of three files.

The names of the files are 61471006, 61471006_2, and 61471006_3.

To load the rasters, I have found I go into these files and load the file of type ".adf". (Is this not true?)

It works just fine for one file at a time. When I load all three in turn, the QGIS layers list shows three little raster icons with tiny "previews" of the area covered; the name of each one happens to be identical to the other two (w001001).

They always load "flat" -- that is, one gray-scale tone. So I use the Properties dialog to stretch to MinMax. When I do, only one of the three will change and show the range of shadings indicative of elevation range. The other two turn black.

How can I get all three to show the MinMax range?

Thank you.

share|improve this question
add comment

2 Answers

When you add your rasters, you need to select this: hdr.adf

Rasters will load under the same name yes, but hdr.

I've just tried in 1.7.4 and 1.9, there are no problems with them, nothing turn black.

Also, you will either need to do minmax stretch for each of the rasters OR after stretching first, press disk button to save you prefered choice of stretch and then load others, they will stretch automatically on load.

share|improve this answer
    
Maxim - Thank you. –  Catlike Apr 3 '12 at 0:19
    
Wait - My menu does not offer the selection [GDAL]Arc/Info Binary Grid (hdr.adf HDR.ADF). –  Catlike Apr 3 '12 at 0:52
    
My menu does have the choice "Arc/Info Binary Grid" but there is no mention of "hdr" or "HDR". The "adf" and "ADF" only appear once window opens upon my selecting "Arc/Info Binary Grid". What to make of this? –  Catlike Apr 3 '12 at 1:03
    
try using that and save your choice of stretch and then load other rasters –  Maxim Dubinin Apr 3 '12 at 3:25
add comment

If these rasters are in effect tiles that adjoin each other it might be worth merging them into one big DEM. In QGIS go Raster -> Miscellaneous -> Merge.

share|improve this answer
    
nhopton -- thank you. That is a great idea; helps organization. –  Catlike Apr 3 '12 at 0:18
    
On first look, it appears straight-forward. But the merge tool does not let me load more than one raster in the "input files" field! How do I get the other two loaded? Thank you. –  Catlike Apr 5 '12 at 10:24
    
When you are selecting the rasters hold down the Ctrl key, which will allow you to highlight all of the rasters you want to merge, one-by-one. Nick. –  nhopton Apr 5 '12 at 11:06
    
I can't get this to work! Each of the adjacent rasters is in its own folder. If I try to move them all into one folder, the fact that they have same-name component files makes that impossible (because it wants to over-write the same-name component files already there). If I leave them in separate folders, the GUI won't let me Ctrl-click and add each in succession -- it replaces the 1st with the second, instead of adding the second. Grrrr! –  Catlike Apr 10 '12 at 5:05
    
How about something like this from a command line: gdal_merge -o merged.tif /path/to/filename.adf /path/to/filename.adf /path/to/filename.adf –  nhopton Apr 10 '12 at 10:10
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.