We received a DTM surface along with the topo DGN. Since we are working in Geopak SS2 mainly, we converted the DTM to a TIN file, but when we display the TIN file, it appears as though it has moved about 4' south of where the topo is. When I visualize the DTM using Geopak SS3, it comes in correctly. Any ideas why the conversion to TIN would cause a shift?
Could it be a survey foot vs international foot issue? I don't use geopak but have seen similar issues.
Charles (Chuck) Rheault CADD Manager
MDOT State Highway Administration
Answer Verified By: kcaitch
If it is an issue with the units, I'm not sure why it will display correctly when I am using the original DTM file. Just in case, I created a DGN file with SF units (the original had plain Feet) and then tried to convert the DTM to a TIN file again, but the results were the same. Until I find the cause of the issue, I will just have to move the triangle elements and then redefine the TIN. But hopefully I can figure out what is happening in the conversion to really solve it.
CADDCOP,
I think you were on the right track. I can't seem to find the units that the TIN/DTM uses, but the Topo CAD file that was also delivered with the DTM had a mismatch in the units. I am not sure how it would have looked in InRoads, which is what they are using, but it obviously didn't work when we got it. After I adjusted the working units so they matched, it shifted the topo up about four feet. I then just had to move that info back down and now everything matches up.
Thanks for pointing me in that direction CADDCOP.
One way to test or to fix issues is to attache a feet file to a survey feet file. Then turn off true scale in the reference dialog box. The scale will change to 1.000002 to 1 or 1 to 1.000002 (or something with less or more zeros). Finally, change the 1.000002 to a 1.0 and the shift will vanish. Merge the reference into master and you will have a file with corrected feet.
This is more accurate than simply moving the data, as it really is a scale from xy-0,00 issue and not actually a shifted origin issue.