LOCAL COORDINATE TO GRID COORDIANTE TRANSFORMATION

[rkmin]

We have a survey done in local coordinates and we would like to convert them to State Plane.

We GPS tied several of the control points but we are not sure on how to actually do the transformation in Autocad Civil 3D 2013 to convert the local coordiantes to GPS coordiantes.

I appreciate any help.

[MtnMax700]

You'll need a scale factor to go from ground to grid, I "move" my local points to a grid point, then I use "scale" about a point and then I "rotate" them to match a  corresponding baseline/basis of bearing.  I'm a "KISS" kind of guy.  I don't use the "Survey Database" and my jobs are fairly small-couple hundred points.

[rkmin]

I have 4 miles of road containing 6500 points. We also would need to do a traverse adjustment since it was an open traverse based on the GPS ties to several of the control points within the job.

Going from grid to local cooridinates, we are able to do a One-step transformation in our Lecia GPS 1200 RX Controller. But there doesn't seem to be a way to go the other direction from the collector. That would have been the simplest way.

[MtnMax700]

Do you have raw or fieldbook file?  Been a while but could you put your GPS coordinates in for the control points, apply a scale factor and rerun the fieldbook file to get grid coordinates?

[sboon]

You should be able to use the Transformation tab in the drawing settings dialog to do this, assuming that you have the parameter data.  First you need to set the correct units and zone.  I typically use a user defined scale factor and shift data supplied by the survyeor.

I've created a few points to show the local versus grid coordinate values.  If the transform settings are turned off the grid values will be the same as the local ones.  If you want to export the grid data then you can create a new Import/Export format which uses the grid fields instead of the local ones.

[rkmin]

Thanks for all of your suggestions. I'm in the process of working with Leica since my GPS equipment and software is from them. I'm not familiar at all in using FBK files so that would be very difficult for me to figure out.

I'm trying to "warp" my local coordinate data to make it fit my GPS data through a coordinate transformation. 

[Bill_Myron]

http://beingcivil.typepad.com/my_weblog/2011/11/from-the-grid-to-the-grounda-conversion-walkthrough....

Give this a read through. Civil 3d can do what you want if you tell it what to do.

[rkmin]

Thanks for the article. Using my Leica Geo Office program, I know how to convert Grid to Ground and then import the modified coordinates into CAD. 

I would like to go the other way from Ground to Grid and not by applying a scale factor only. Normally, if I wanted to get my GPS coordinates to local coordinates, I can do so straight from my Leica GPS controller. I have my local coordinate files loaded into my controller, I shoot several common control points with the GPS and then I can process a coordinate transformation using 4 or more common points to convert my GPS data onto my local data. Even if my local control points don't have perfect closure, the GPS points will "warp" itself to make it fit my local data showing me the northing/easting errors. I'm not concerned about elevation. And all this is by not simply applying a scale factor.

Now I would like to go the other way. I have a different job that was all done using a total station, and I would like to make that local coordinate points (using assumed 10000, 10000 coordinates) fit into my GPS coordinates that I shot for several of the common control points. Since I started with assumed coordinates with an assumed bearing, I need it to scale, rotate and translate my local data so that it fits reasonably close to my GPS data.

I'm very grateful for your guys' help and suggestions. I realize it might be a daunting task that I have posted here. I figured going from GPS to Local coordinates is a rather simple process from my controller, going the other way shouldn't be so tough either right? But maybe it is and I just don't realize it.

[doni49]

Assuming that there are two points that you know the horizontal location in the new system and the old assumed system, this should help.  It's something I wrote last year for use here at work.

[surveyor8120]

You say you are using Lieca.  Do you have the datum and map option for lieca on your computer?
You can create custom local coordinate systems on your computer, just like you do with your lieca data collector.

In Civil 3D you can also create custom local coordinate systems.

There are a couple different ways to do all of this.  Just depends on your specific needs.

If you need help, I also have put together some how to documents for in house use, they I can send you.

Email me and set up a time to chat and I can walk you thru it.

Anthony Robinson

arobinson@crweng.com

907-646-5617