AutoCAD Civil 3D General Discussion

AutoCAD Civil 3D General Discussion

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Valued Contributor
CityWF
Posts: 56
Registered: ‎05-13-2005
Message 1 of 8 (469 Views)

no datum vs nad 83

469 Views, 7 Replies
02-12-2013 08:01 AM

Im working in acad c3d 2013. To help my question be easier to follow, open a drawing, on the tool space click the settings tab, right click on the top folder/drawing name, click edit drawing settings.

 

If I edit the drawing settings  to the Zone- USA, Texas, and the cood system to nad83 Texas State Plane, North Central Zone, US Foot, then it changes the imperial to metric conversion to US survey foot. then when I bring in my points they are about 15 feet off.

If I set the Zone to NO Datum, NO Projection  and the Imperial to Metric conversion to International foot , then they come in correct.

 

Can anyone explain this. I thought it should be in nad 83. As far as I know the survey equipment is set up correctly.

Valued Mentor
stacy.dunn
Posts: 386
Registered: ‎10-03-2008
Message 2 of 8 (450 Views)

Re: no datum vs nad 83

02-12-2013 09:34 AM in reply to: CityWF

The difference you are seeing in your coordinates is due to the US-Foot/Int-Foot conversion.  The difference is only 2ppm, but when applied to the large coordinate values of this zone it equals the 15-foot displacement.

 

What foot unit is the data using?  What are you comparing the imported points to that you know it is "off" when the foot unit is changed in the drawing? 

 

 

Stacy Dunn
*Expert Elite*
Adriano_cad
Posts: 105
Registered: ‎06-21-2011
Message 3 of 8 (440 Views)

Re: no datum vs nad 83

02-12-2013 10:02 AM in reply to: CityWF

Hi,

 

Are you doing the import using the Survey? or just are importing a file of points (N, E, Z) .....

 

If using the Survey, then you need to do the configuration of units with command AeccEditSvDatabaseSettings.

Adriano Oliveira

*Expert Elite*
MaxiCAD Informática
www.maxicad.com.br
Valued Contributor
CityWF
Posts: 56
Registered: ‎05-13-2005
Message 4 of 8 (431 Views)

Re: no datum vs nad 83

02-12-2013 10:33 AM in reply to: CityWF

Stacy- It Defaults to US Survey Foot when I pick TX83-NCF for my coord system,

It works perfect with international foot but what else does the "no datum" affect?

I am using the control point N&E off the field notes to check if its in the correct location. plus its really obvious when its layed over the topo map

 

Adriano- the settings are set to no datum

Valued Mentor
stacy.dunn
Posts: 386
Registered: ‎10-03-2008
Message 5 of 8 (431 Views)

Re: no datum vs nad 83

02-12-2013 11:04 AM in reply to: CityWF

The foot unit should be US-Foot when selecting TX83-NCF.

 

The zone must be set to allow Civil 3D to calculate grid coordinats, Lat/Long and grid distances.  The zone information is also used to transform GIS data, data from a survey database, and point data where the file format contains zone information.

 

It is important that you know what units/zones your data is using and what the settings your drawing and survey database are using.  If your survey database is set to USFoot and the drawing is set to International Feet, the data will be adjusted when inserting it into your drawing.  Civil 3D expects you know what you are doing and doesn't warn you that the adjustments are being made.

 

If this is a new project I would verify that all of your data has been imported into the drawing correctly.  If this is an existing project, you may be better off leaving the zone off and continuing with the current coordinate system.

Stacy Dunn
Valued Contributor
CityWF
Posts: 56
Registered: ‎05-13-2005
Message 6 of 8 (408 Views)

Re: no datum vs nad 83

02-12-2013 02:46 PM in reply to: stacy.dunn

I can only get it to come in correctly with the drawing settings set to international foot, no datum-no projection

It doesnt change anything when I edit the survey database settings.

The weird part about it is its been working fine on the nad 83 setting- us foot so I am wondering if there is another setting somewhere. We had trouble about a year ago with one project, I dont know what I did to fix it and today I cant get any of them to work.

 

Valued Mentor
stacy.dunn
Posts: 386
Registered: ‎10-03-2008
Message 7 of 8 (375 Views)

Re: no datum vs nad 83

02-13-2013 12:07 PM in reply to: CityWF

I am guessing here, but is it possible that the coordinates you are importing are using the wrong foot unit?  Can you compare the coordinate value of the original file to the one you end up with in C3D and see if something has been adjusted in the import process.

Stacy Dunn
Valued Mentor
IanMcClain
Posts: 455
Registered: ‎09-29-2008
Message 8 of 8 (358 Views)

Re: no datum vs nad 83

02-13-2013 06:00 PM in reply to: CityWF
How are the coordinates being added to the drawing? From points import or a survey database? Can you post the coordinate file or a portion of it?
-Ian McClain
(running C3D 2012 sp4, Win7 64bit, 8GB)
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