I am issues with DEM files that I am downloading from the USGS website.
I download 24k, elevation for the area I need. I then choose staged 1 second, add a surface to a blank drawing, then upload the DEM files to the surface.
The surface imports correcty, but when I try to import points taken by a surveyor on the same drawing, they plot incorrectly.The DEM surface and the points from the surveyor do not correspond. Also, the DEM surface is in meters, not feet.
What am I doing wrong? I have tried changing drawing settings, datum types, coordinate types, etc.
Look at the Metadata regarding the DEM to confirm that it is in the system you expect. Then verify the system and datum of the survey data and how it was determined. After you've confirmed that and it still doesn't work should you look for errors in the software or your procedures.
You say the datum is in meters. Are the survey points also in meters?
I will check into this, thanks for your quick response. My theory was that the survey points need to be converted to correspond with the DEM data, but that still doesn't explain why the datum imports in meters when I specify feet when setting up the drawing.
The survey data imports in feet.
I don't work with DEMs much. It looks like you have to enter the information on the DEM manually. At least in the test I did. Hopefully the survey points are in a defined system, not a local one. If they're not in a defined system the only way to "convert" them to the system you import the DEM in would be by eyeball. Hopefully things will look better when you get the DEM in in Feet.
Actualy it looks like I had the first try wrong. I think this one is better. Also: make sure whether you need to import as International Feet or US Survey Feet.
Here is the problem I am having. Here are the steps I took:
1) Assigned a coordinate system to the drawing
2) I created a new TIN surface
3) I added the DEM surface from the Prospector (Surface - Definition - DEM files)
Here is the problem:
4) (see attached) attempted to change the coordinate system of the DEM but unable to do so.
Any suggestions? Thanks in advance.
Thanks for the quick response. Unfortunately that didn't work. I know what I did wrong. I didn't add the coordinate system when I initially added the DEM file. When I went into the properties to add the coordinate system later, I didn't have the option to do so. So to whomever read this, make sure to add the DEM coordinate system with the DEM file at the same time. Otherwise your DEM surface will come in some random location and size
For some help with bringing DEM files directly into C3D, see this post I did a while back:
Just FYI, that post is great. I printed it and placed it in my continuity folder (also saved as my favorites)
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