topic Re: DEM problem in Civil 3D Forum

DEM problem

JimJonesPELS — Tue, 19 Apr 2022 04:29:35 GMT

I have downloaded a DEM file for White Salmon, WA and the data is there but nothing is displayed on the screen. See attached.

Would appreciate some help.

Thanks,

Jim

Re: DEM problem

Pointdump — Tue, 19 Apr 2022 05:56:20 GMT

Hi Jim,
When I click on the rectangle, the Properties Windows says it's an "ACAD_PROXY_ENTITY". So that's kinda baffling. Can you post your data or a link to where you got it?
Dave

Re: DEM problem

JimJonesPELS — Tue, 19 Apr 2022 13:43:43 GMT

Morning Dave,

See attached.

Thanks,

Jim

Re: DEM problem

Pointdump — Tue, 19 Apr 2022 13:58:05 GMT

Jim,
I'm not seeing anything in your drawing except for this "ACAD_PROXY_ENTITY". Where did you find data and how did you import it into Civil 3D?
Dave

Re: DEM problem

JimJonesPELS — Tue, 19 Apr 2022 14:19:31 GMT

Dave,

I googled "DEM data Washington" or something like that and found the data. I can't find it again. Asking me to do anything twice is a real challenge in this game.

I created a surface and imported the DEM file from there. The date does show up in the surface I created.

Any suggestions are welcome.

Re: DEM problem

Pointdump — Tue, 19 Apr 2022 14:36:48 GMT

Jim,
I understand completely about not being able to find something again. That's an everyday thing for me.
I don't see a surface in your drawing. There is only 1 object. When I assign a UTM83-10 coordinate system to your drawing, that rectangle covers a lot of ground on both sides of the river.
I found some good data >>>Here<<<.
Dave

Re: DEM problem

ChicagoLooper — Tue, 19 Apr 2022 14:45:29 GMT

You can find DEM data >>HERE<<.

To download, follow steps 1 through 6 below.

Re: DEM problem

JimJonesPELS — Tue, 19 Apr 2022 14:46:05 GMT

I have mastered the screen shot! I hope you can read. I created the surface so I could import the DEM file after I downloaded to my "C" drive. I reattached the drawing. No idea why the surface wouldn't be there.

Let me know if that's the case and I'll try working on your link.

I'll be away from my desk the next few hours.

Thanks,

Jim

Re: DEM problem

JimJonesPELS — Tue, 19 Apr 2022 14:47:59 GMT

Thank you.

I'm away from my desk the next few hours and will try later today.

I appreciate your help,

Jim

Re: DEM problem

AllenJessup — Tue, 19 Apr 2022 15:35:19 GMT

Based on your screenshot. It looks like you have a Surface Style that only shows the Boundary. You'd need to set (or create) one that shows the contour interval you want.

Right click on the Surface in the Prospector tab and select Surface Properties. Set a Surface Style that shows contours.

Re: DEM problem

JimJonesPELS — Tue, 19 Apr 2022 17:48:32 GMT

Thanks.

I actually I had to turn the lights on for the layers. I can now see the contours in the drawing.

Unfortunately, I can't fix the contours to the drawing after hitting zoom extent.

Re: DEM problem

ChicagoLooper — Tue, 19 Apr 2022 18:03:28 GMT

You have a problem with your data:

It's not being read correctly (or there isn't anything to read to begin with)
You haven't added it to modelspace correctly (refer to image below).

If you are drawing in Washington State Plane, South Zone, NAD83, feet, then your surface is too far North. (White Salmon, WA is in South Zone.)

A DEM is a geospatial entity and this means you are dealing with two coordinate systems: (1) the native coordinate system of the DEM and (2) the coordinate system that is 'assigned' to modelspace.

If you don't assigned a CS to your drawing, then the DEM won't know where to go in modelspace. Also, if you don't tell your drawing the DEM's native CS is using 'this' CS (or don't verify the DEM's true CS is being used) then an incorrect CS might be applied to the DEM by mistake and this will cause the DEM to insert improperly.

Re: DEM problem

AllenJessup — Tue, 19 Apr 2022 18:12:23 GMT

@JimJonesPELS wrote:

Unfortunately, I can't fix the contours to the drawing after hitting zoom extent.

I don't know what that means. A wild guess would be LEVELOFDETAIL.

Re: DEM problem

ChicagoLooper — Tue, 19 Apr 2022 18:38:13 GMT

Based on your uploaded drawing named JTJ.dwg you are drawing in Washing State Plane Coordinate Sytem, South Zone, NAD83, US feet.

Here's a zoomed-in screenshot of your site. You can clearly see Bing aerial imagery is consistent with your line work. This is good, it's drawn correctly. Excellent! Refer to image-1.

Image-1.

If you use the same image above and zoomed-out, you'll see your DEM surface is to the North, probably in Canada (or maybe the Arctic). Bing aerial imagery is at the bottom of the screenshot. Bing imagery covers Washington State Plane, South Zone, NAD83. Refer to image-2.Image-2.

Your surface, the one you're creating with the DEM, should be at your site and consistent with the utilites, roads, parcels, etc.

Re: DEM problem

Pointdump — Tue, 19 Apr 2022 19:23:52 GMT

Jim,
The best elevation data I found is from the >>>DOGAMI<<< site. The data is really dense, pixels spaced at less than a foot. In QGIS I cropped the huge ADF file(659MB!) down to a manageable 3.6MB. That still gives you a surface of 684,203 points over your area of interest. Attached, please find WhiteSalmon_2286.tif. Assign your drawing a WA83-SF coordinate system and set the tif's coordinate system same.
Your survey points from JTJ.dwg fit nicely and elevations match.
Dave

Re: DEM problem

JimJonesPELS — Tue, 19 Apr 2022 19:43:55 GMT

Thanks CL. I'm sure you've nailed it. Thing is - you're dealing with a new boy here. Baby steps please.

1. I don't know how to put the Bing map background into my drawing.

2. I can find the two locations, one in Washington and the other in Arctic, but don't know how to correlate the two i.e. copy one onto the other.

Any instruction for someone with my problems?

Thanks again,

Jim

Re: DEM problem

JimJonesPELS — Tue, 19 Apr 2022 20:51:47 GMT

Dave,

That worked perfectly. The contours came in and seem to fit (see attached). I can't select the contours individually and they're not labeled. I also not noticed that when I zoom out the minor contours disappear and reappear when I zoom in. Any idea what's going on there?

Also, how did you get the background aerial?

Thanks,

Jim

Re: DEM problem

Pointdump — Tue, 19 Apr 2022 21:07:54 GMT

Jim,
Looks like you're making headway.
The contours disappear at different zoom levels because of command LEVELOFDETAIL. You can turn it off, but performance will suffer.
You won't be able to select any of the contours. They're not an AutoCAD object, they're a Civil 3D object.
In the Annotate Tab >> Labels & Tables Panel >> Add Labels dropdown you'll find several ways to label the contours.
To get Bing Live Maps click the Geolocation Tab >> Online Map Panel >> Map Off dropdown.
Dave

Re: DEM problem

JimJonesPELS — Tue, 19 Apr 2022 21:47:45 GMT

Dave,

Thanks for your help.

Jim

Re: DEM problem

ChicagoLooper — Wed, 20 Apr 2022 01:18:50 GMT

Source:

The National Map (TNM)

Instead of DEM, download shapefile. Compared to raster data such as DEM, shapefile is vector and much easier to work with when compared to raster data. Shapefile data also includes a projection file (prj) so there's no guessing what the native coordinate system is being used by the shapefile. Image-1.

Image-1

If you can click a mouse, you can search for and download free elevation data in shapefile format. The download is immediate, no need to set up an account and no need to disclose you email address. Image-2.

Image-2

The search result and the download link. Image-3.

Image-3

The TINN surface has been built. Typically the contours from a shapefile are smooth and fluid, DEM contours, on the other hand, tend to be jagged. Image-4.

Image-4