Author Topic: how do I access USGS map files manually to get to the greyscale map (Read 328 times)

Citabria · « **on:** February 04, 2004, 07:16:50 AM »

is there a program or a way that you can pull greyscale maps directly from usgs files and edit them in photoshop?

Dux · « **Reply #1 on:** February 04, 2004, 07:20:43 AM »

Cit, if you can find a good DEM or DTED file to use, a freeware program called MicroDEM is a pretty good tool. You can stitch together multiple DEMs if you need, then export them as a single TIFF file (then you can convert it to a BMP).

If you do, make darn sure you don't have any 3-D shading turned on. See the example below: The left image is a portion of a raw, unfiltered DEM. The right image has been shaded to look 3-D to your eye, but is wrong for the purposes of the AHTE.

Correct...................... ...................... Incorrect.

Remember: the grey value directly translates to an elevation; when the data is given highlights and shadows, that elevation value gets altered.

NHawk · « **Reply #2 on:** February 04, 2004, 10:56:31 AM »

Photoshop can open DEM files directly..

1) Click FILE
2) Click OPEN AS
3) Select RAW
4) .. Raw Options

Width: 4800
Height: 6000

Channels:
Count: 1
Depth: 16bit
Byte Order: Mac

Header Size: 0

5) Click OK

The file will open.

6) Click Image
7) Select Adjustments/Levels
8) Adjust levels to the point you're happy with grayscale output.

Citabria · « **Reply #3 on:** February 04, 2004, 02:23:49 PM »

thanks!