AutoCAD Civil 3D General Discussion

AutoCAD Civil 3D General Discussion

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Active Contributor
Thewitt
Posts: 45
Registered: ‎02-13-2009
Message 1 of 8 (307 Views)

Survey Database Coordinates differ...

307 Views, 7 Replies
03-09-2010 01:08 PM
I'm having trouble getting my coordinates in Civil 3D to match my coordinates in my Trimble TSC2 data collector when I process the data though the survey funtionality of Civil 3D. I can successfully get the points that were located with GPS to match correctly with C3D and the data collector. The issue are the points that were collected with a total station. When I process the work in Civil the coordinates do not match. I'm only talking a hundredth to a couple thousandths, but I'm a surveyor that strives for accuracy. I have adjusted all the different settings. I have found that when I only use the the Sea Level correction my coordinates almost are exact. I understand Civil strips all the corrections that my data collector applies and then reapplies based upon Civils formulas. I am just curious if anyone else has experienced this and if they have, what have they done to correct this issue.
*Matt.Anderson
Message 2 of 8 (307 Views)

Re: Survey Database Coordinates differ...

03-09-2010 06:56 PM in reply to: Thewitt
My understanding is that Trimble export removes the adjustments when
exporting to a FBK file. Civil 3d doesn't remove them, but Trimble Link
does so that Civil 3d can readjust them there.

Matthew Anderson, PE



thewitt wrote:
> I'm having trouble getting my coordinates in Civil 3D to match my coordinates in my Trimble TSC2 data collector when I process the data though the survey funtionality of Civil 3D. I can successfully get the points that were located with GPS to match correctly with C3D and the data collector. The issue are the points that were collected with a total station. When I process the work in Civil the coordinates do not match. I'm only talking a hundredth to a couple thousandths, but I'm a surveyor that strives for accuracy. I have adjusted all the different settings. I have found that when I only use the the Sea Level correction my coordinates almost are exact. I understand Civil strips all the corrections that my data collector applies and then reapplies based upon Civils formulas. I am just curious if anyone else has experienced this and if they have, what have they done to correct this issue.
>
New Member
RandyR4321
Posts: 1
Registered: ‎04-09-2014
Message 3 of 8 (155 Views)

Re: Survey Database Coordinates differ...

04-09-2014 01:44 PM in reply to: Thewitt

I have the same problem / concern and would like to know if you got this resolved.  And what that resolution might be.

 

This is the only post that I have ever found that has noticed this situation.  I am so tired of reading about US foot, feet and international feet.

 

years ago our office upgraded to C3D 2010 and found the same problem and resolution you mention (sea level).  I refrained from using 2010 and continue to use LDD to import FBK data.  Now the office is running 2012 and moving to 2014.  The same problem exists.  The error gets greater the further away the measurement is from the instrument.  I've seen error up to .04 around 600-700 feet from the instrument.

 

the issue I see is when I mix different types of measurements with different collectors.  I start with GPS measurements to establish control points (and to topo with).  The GPS control is then utilized with conventional equipment all of which are 5600 robots, using a TSC3, TSC2 and TSCe collectors.

 

I make field books with Trimble link.  I first import the GPS field book which establishes all the control for the 5600 robots.  Then I import the conventional equipment data (removing the inputed coordinate values).  I import the TSC3, TSC2 and TSCe fbk files.  When I compare coordinate within the respective collectors, the TSC3 and TSC2 data is really close.  The TSCe data contains the most error.

 

All the FBK file headers are the same.  Prism constants are the same.  FBK units are the same.

 

Remember, I am using 4 collectors on the same job site.  If I import each FBK file in an individual drawing, the error from the autocad coordinate relative to the collector coordinate is much much smaller.  Darn near perfect.  But now I have four autocad files with points in them that need to be combined in to one file for drafting.  Then there is the issue with download each collector every couple of days to add more data.

 

Any input on what you know is greatly appreciated.

 

randy.rosson@stockassoc.com

*Expert Elite*
Pointdump
Posts: 793
Registered: ‎11-24-2009
Message 4 of 8 (139 Views)

Re: Survey Database Coordinates differ...

04-10-2014 02:56 AM in reply to: RandyR4321

Randy,

Welcome to the C3D Forum.

Need more specifics. Are your data collectors all using the same software and version? Are you using Carlson, Survey Pro, Survey Controller, Access?

I know you're "tired" of reading about the difference between Survey Feet and International Feet, but it's the easiest and first thing to check, in your data collectors as well as your survey database.

Can you provide a table of some points that have differences? Establish a pattern, then you'll find your solution.

Dave


Dave Stoll
Mohave Valley, Arizona

Intel Core i7-3820QM 3rd Generation Quad Core 2.7 GHZ CPU
16 GB DDR3 RAM ( 2 DIMM ) / 180 GB SSD
Nvidia GeForce 650M Graphics w/2 GB Memory
Windows 7 Professional 64 bit / AutoCAD Civil 3D 2014/2015
Valued Mentor
KirkNoonan
Posts: 429
Registered: ‎09-23-2008
Message 5 of 8 (121 Views)

Re: Survey Database Coordinates differ...

04-10-2014 06:07 AM in reply to: RandyR4321

From your description, I'm not 100% sure if this is your issue or not. We've noticed that if you re-shoot the GPS control points with the total station that the software will overwrite, or average (depending on settings) the GPS point with the total station point. Our solution has been to import the control from the GPS separately as control points. When the points are defined as control points in the database, subsequent imports won't modify them.

Active Contributor
Thewitt
Posts: 45
Registered: ‎02-13-2009
Message 6 of 8 (112 Views)

Re: Survey Database Coordinates differ...

04-10-2014 06:45 AM in reply to: Thewitt

I have not found a solution.  I've contacted Trimble and Autodesk and no one seems to have an answer for me.  I still process my data in TGO and import linework into C3D.  The only work around I found is to export a text file from our TSC2 and I can process the text file in C3D.  I prefer TGO processing over C3D because there are more linework code options in TGO.

Valued Mentor
IanMcClain
Posts: 455
Registered: ‎09-29-2008
Message 7 of 8 (104 Views)

Re: Survey Database Coordinates differ...

04-10-2014 07:18 AM in reply to: Thewitt

Can you post one of these suspect FBK files, a csv version of the same points and what the coordinate system projection settings are/should be?

-Ian McClain
(running C3D 2012 sp4, Win7 64bit, 8GB)
Distinguished Contributor
cbaildon001
Posts: 163
Registered: ‎06-28-2008
Message 8 of 8 (85 Views)

Re: Survey Database Coordinates differ...

04-10-2014 01:50 PM in reply to: IanMcClain

As you said in your original post you are only talking about 'a hundredth to a couple thousandths' (assume thats thousandths of feet?). Is this significant or is it within the stated accuracy of your survey anyway.

 

As suggested if you use GPS for control, import those as 'control points' so that any total station data won't affect it, or for setup points in a field book ensure they are listed as NEZ at the top of the field book and not NE SS, so that they also come in at the data logger coordinates.

 

Also as you suggested, the only correction that should resonably be done in Civil3D is the Sea Level correction so that ground distances are reduced to ellipsoid distances. This is one area where slight differences can occur, for example in one test I did I found:

 

"I did a test to compare the resultant ellipsoid distance of an observation on an NZGD2000 meridonial circuit at elevation 3000m and a measured ground distance of 10000m. My TSC2 gave a distance of 9995.299m, Civil3D 9995.291 (or 0.8ppm), so in essence identical."

 

If this is the only correction turned on then differences should be negligible.

 

Regards

Caleb Baildon
Surveyor
Opus International Consultants Ltd
Greymouth, New Zealand
Civil3D 2015 - Windows7 64bit
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