Topic: Edit Coordinate Systems

[dfarris75]

I have a drawing set up in NAD 27 Zone 17 with a dem surface added. I want to bring in doqqs which are in NAD 83 FL East Zone via data connect. I was under the impression that the Edit Coordinate Systems would allow me to do this, but they (doqqs) just plop right into the same place. Am I using the tool incorrectly or must I create a separate .dwg with the doqqs in their zone and then query that .dwg in???

[dfarris75]

BLING!!! I figured it out. I was using it incorrectly. I was inputting the dem file coord zone in the Edit Coord... deal when I was supposed to be inputting the sources coord zone...
Thanks for all your help!

[Dinosaur]

sure . . . any time . . . glad to be of service 

[dfarris75]

Hehe. Now I guess my next question is, why are DEM's so squarish in nature? My contours are all jagged.

[Dinosaur]

they are based on a grid of given resolution . . . the entire area of each square on that grid is assumed to be at the same elevation - kind of like a bunch of building blocks stacked in columns of different heights

[dfarris75]

Hmmm. And I guess there's really no way to smooth them out so they're a little more aesthetically pleasing.

[Dinosaur]

You might try some of the smoothing options or min / max triangle lengths in your surface style.  I have neither working C3D nor DEM data right now to check.

[dfarris75]

Smoothing is on and set around 7. I don't think adjusting max. triangles will help. Oh look. It's lunch time.

[Dinosaur]

The problem is you have a lot of hard data sitting exactly on a contour elevation.  I have no clue if this will have any effect, but what happens if you raise or lower the entire surface some percentage of a foot?  This is very low precision data anyway.

[Jeff_M]

I had the same problem (I guess we all would if we all used DEM's...) so I wrote a little lisp that weeds the contours and gives a decent looking contour. However, I found that using Google Earth gives just about the same results and is far easier than getting the DEM's.

I'll post the lisp if you'd like to give it a shot.

[dfarris75]

Sure. What the heck. May as well have it available in the lisp arsenal anyway.

[Jeff_M]

OK, here ya go. The lisp to load is "weed-nineties.lsp" and the command is "desquareconts". Select the contours to smooth out and wait while it works. It isn't ideal, but for the job I created it for the client was happy.

[dfarris75]

And to verify, this is for Civil 3D surfaces or no?

[dfarris75]

Doesn't appear to...

[Jeff_M]

Oh, my apologies I should have clarified......
Create your C3D surface from the DEM,
Use the Style for the contour display as you please,
Extract the contours,
Use the lisp on the resulting polylines,
Create a new surface from the modified plines.
Set the original DEM surface to No_Display


Like I said, Google Earth is a bit easier