International Feet DEM coming in with US Survey Feet

[BrianHailey]

I have a DEM that when I add it to a surface (or create a surface directly from it), it comes in shifted off the true position by the scale factor between US Survey feet and International feet. If I bring the DEM into the drawing using the MAP 3D data connection tools, it comes in correctly. Any idea what's going on or how to fix this?

The drawing has a NAD 83 international feet coordinate system assigned to it and the DEM file has the same coordinate system. It's very odd.

[Pointdump]

Hi Brian,
Any scale shift with International Feet/US Survey Feet problems will be in a NorthEast or SouthWest direction. The shift you're showing is NorthWest/SouthEast. Usually that screams Datum Shift.
Can you post the DEM and the drawing?
Dave

[rl_jackson]

Set INSUNITS = 0 (Unitless) and try to bring it in. 🙂

[ChicagoLooper]

What’s the source if the DEM? Do you know the author or was it downloaded? Can you share the link?

[BrianHailey]

Thanks everyone for replying. I was out at the end of last week sick so I wasn't able to reply. 

Unfortunately, I'm not able to share the file. I asked for permission and was told I couldn't share. It was created internally from another GIS system. It comes in perfectly when using the MAP 3D tools but off when using Civil 3D.

This is a US Survey Feet vs. International Feet issue. If I scale the surface around point 0,0 by a factor of 0.999998, then it looks spot on. Apparently, Michigan State Plane coordinate systems are very skewed to the east (the point on that peninsula is at N:765,536.13 E:13,156,933.38.

As for the drawing units, they don't seem to make a difference. I've tried the drawings units set to unitless, feet, and us survey feet and the surface created using the dem always comes in at the same, incorrect location. I've even tried assigning different coordinate systems to the DEM as I add it to the surface to see if that would make a difference and it didn't.

The DEM has the coordinate system MI83-SIF as does the drawing. 

Hopefully something I've written here will spark a memory or an idea.

Thanks!

[BrianHailey]

So, it seems to be a bug in 2023. Here's the same data brought in using 2020:

Time to see if I'm missing an update.

[BrianHailey]

Nope. The 2023.2 update didn't fix it. Time to report it to Autodesk.

[Pointdump]

Hi Brian,

Keep us in the loop on this one.

Dave

[BrianHailey]

I submitted it to Autodesk. One suggestion was to roll back to no service packs in 2023. I did that and it's still happening. They are going to escalate this up to development so hopefully it will be patched soon. In the meantime, I'm installing 2020 on the machines of our users that need to use this functionality.

[cwitzel5NL5H]

I am wondering if there is any update on this?  I see in the release notes for 2024 that it is "fixed".

I see no mention in any of the 2023 SP release notes.

It seems to me that this needs to be a better advertised fix.  As it currently requires a work around that would or could produce incorrect results if the work around was used after the fix.

Thanks,