Cropping an ASCII DEM...

[wojo]

My DEM file is an entire USGS quadrant... hundreds of times more than I need. I know I can import the approximate terrain area I want by windowing it in the viewer as you import it, but there's no accuracy in that process. I think I have a better idea if it can be done...

If you could produce a set of ASCII points that includes only your golf course area, you could drop the terrain exactly onto a new course of the same dimensions. I've gone into Google Earth and determined the borderlines of the area I want.. (N44.8920, N44.8843, W124.020, W124.040). Does anybody know of a DEM supplier that can create an ASCII DEM of a rectangle from coordinates?

The only other option I can think of is if you can identify and delete the extraneous points in the ASCII DEM file... either manually (sounds pretty tricky) or maybe there is or was a software that could zoom in on the set of points you need and delete the rest?

Anybody ever heard of anything like this?

Wojo

[alarduran]

Hi, wojo.
If you would want to, I could try to crop your DEM file to the desired limits (N44.8920, N44.8843, W124.020, W124.040) with a GIS software I am used to. Just make me available the DEM file by some way you prefer (WeTransfer, private message, ...).
Regards.

[wojo]

Thanks, Alarduran... I'm attaching an image of the target area. The coordinates are different (a larger area) than those I listed earlier. They are... W124.020, W124.038, N44.8776, N44.8956. It looks like I can't attach a DEM file here. Can you send me an email address via private messages?

[Danny D]

Thanks, Alarduran... I'm attaching an image of the target area. The coordinates are different (a larger area) than those I listed earlier. They are... W124.020, W124.038, N44.8776, N44.8956. It looks like I can't attach a DEM file here. Can you send me an email address via private messages?

Hi wojo. Unfortunately, we can't attach files to private messages. We normally use Dropbox, or some other site to upload files to, and then send the download link along with a private message.

Dan

[wojo]

Just noticed I can send a DEM file if it's zipped...

Thanks.

[alarduran]

Hi, Wojo.

You have a pm.

Regards.

[wojo]

I don't understand. What's a "pm"?

[wojo]

Never mind... I got the files you sent. Thanks.

Wojo

[alarduran]

P.rivate M.essage
Sorry. I've gotten used to the slang of this place...

[wojo]

What coordinates did you use to crop the DEM? (I know I might have confused you with the two sets of coordinates and images I gave you... My bad.) Something's not working with the DEM vs. known dimensions on the course. I applied the overhead image (attached) and scaled it so it lines up top to bottom to the top and bottom edges of the DEM. There's a red diagonal line in the image. When I measure that diagonal line in Google Earth it's 1533 yards long. When I measure the same points in APCD, it's over 2,000 yards.

I'll attach the correct image again. If it helps, the yellow box should measure about 1,555 yards horizontally and 2,190 yards vertically. If you look at the yellow box on the image, the coordinate lines are W124.020, W124.038, N44.8776, N44.8956.

Thanks in advance for checking.
Wojo