Civil 3D objects and coordinate systems

[demus72]

I have a drawing with an alignment, surface, and a couple profiles in NAD83. Our surveyor will be setting up some control points for construction staking, and of course, prefers working in State Plane. I have done some research before on this subject but as I recall, Civil 3D objects cannot be transformed using a query.

What is the process to transform Civil 3D objects from one coordinate system to another?

Thank you

[tcorey]

FYI: NAD83 can refer to a state plane coord sys. For example NAD83 California State Plane, Zone 1, US Foot.

If you do indeed need to translate from one coord sys to another, start with the points. Export to an ASCII file, set up a Point File Format that specifies the coord sys of the ASCII file, create a new drawing and assign the new coord sys. Import the point file using the Point File Format you created earlier and check the box to do coordinate transformation if possible.

The surface can be re-created from the points. The alignment can be exploded into a polyline and Map Query can be used. Profiles can be re-created from the new updated data.

[stacy.dunn]

NAD 83 is a datum and not a coordinate system.  The points could be translated from your project coordinate system to a state plane coordinate system but in my experience this is a bad idea, especially during construction.  A surveyor can use any coordinate sytem that you are working on to set stakes. 

[Neilw_05]

Have you considering using LandXML to provide the data for the surveyors? LandXML will transform the data when imported into another coordinate system. Of course that won't transfom your C3D objects so you would have to repeat the process for every update, but it might be a workable option.

[antoniovinci]

I don't know US coords system, but I'd bet that "european" traditional approach will work for you, sir.

1] open the Nad83 drawing
2] _ADESETCRDSYS and set the right reference system on Nad83 datum
3] save and close
4] open a new empty drawing
5] _ADESETCRDSYS and set your favorite State Plane
6] _ADEDRAWINGS and attach the Nad83 drawing
7] _ADEQVIEWDWGS to view the transformation result

Now try to input the surveyor's points: how do they fit...?

[AllenJessup]

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@Neilw wrote:

Have you considering using LandXML

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That would be my first option. Either to send data to the Surveyor or to create a new drawing to set points in the required system. As mentioned. Define what difference there is between NAD83 and State Plane in your case.

Allen

[Sinc]

How do you get C3D LandXML to transform coordinate systems?

I've seen it transform units.  And of course, there's the manual translation/rotation parameters in the LandXML Import Settings.  But I've never been able to get it to do a coordinate transform on anything...

For example, the only way I've ever been able to transform a Surface is to run a Map query on the TIN triangles.  Other things have to be exploded or exported to plain Autocad entities, like tcorey said, then a Map query will work on them.  I've never had luck with LandXML (even if everything could be exported/imported via LandXML...).

[Neilw_05]

You are correct that C3D does not transform LandXML data Richard. As stated in the help system:

"It is important to note that LandXML does not transform coordinate systems automatically. Therefore, no specific coordinate system transformation is applied other than what is specified by the translation and rotation settings. For more information, see Translating and Rotating LandXML Data in theAutoCAD Civil 3D Help."

Perhaps the surveyors have access to software that can read and transform LandXML data for their purposes. I think some of Bentley's software can transform LandXML data. Perhaps Carlson and Trimble as well.

[AllenJessup]

For point transformation I rely on good-old CORPSCON. It's the basis of any transformations in Map or C3D and it's FAST. But it just does points. I have done a few polyline transformations with it. But that's just tedious and unnecessary with Map.

For the rest of the drawing you may be able to get away with using Move, Scale and Rotate (some like using Align). This will depend on the size of your project and the scale factor for your area. If your working in a ground based system this should be adequate.

Allen

[antoniovinci]

Another "must-have" to reproject every kind of shapefile is the opensource Mapwindow_GIS...

[AllenJessup]

I suppose you could use Create Blocks from COGO Points, transform the drawing with Map then convert the blocks back to COGO Points.

Allen

[demus72]

Thank you all for your comments and suggestions. I must apologize, the drawing I am currently working in is UTM NAD27 not UTM NAD83. So I need to go from UTM NAD27 to UTM NAD83 State Plane. Sorry about that.

Unfortunately, I don't have any points. This is a very preliminary design that I traced contours from a Quad map, assigned the elevation to each and then used them to define my surface as contours. What I ended up doing was performing a query on my 3D polylines from my surface and a polyline representing my alignment through Map to transform them to the State Plane Coordinate system. Then I redefined my surface and alignment and was able to reproduce the profile and profile view. It was pretty painless but took some extra time compared to simply having the ablility to transform Civil 3D objects from one coordinate system to another. Maybe with the next release?

Thanks again.