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Serious Coordinate Conversion Issue

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Message 1 of 26
kkuecker-traffic
1880 Views, 25 Replies

Serious Coordinate Conversion Issue

My company has been encountering this issue since we switched to AutoCAD C3D.  We used to work in 2011 and now 2012

 

We believe it has something to do with the conversion of International Feet to US Survey Feet.

 

We obtained MicroStation DGN's of alignments we needed to incorportate into our design.  When we attach  the DGN to our DWG it registers to a different point that in the DGN. 

 

The shift is equal to the conversion of International Foot to US Survey Foot mutliplied by the linear distance from orgin (0,0).  (Using one International Foot equals 0.999998 US Survey Feet)

 

We have tried different things such as defining the coordinate system in the C3D file before attaching the refernce, and verifing the original MicroStation file was in the correct coordinate. 

 

We still get a shift in X,Y coordinates.

 

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25 REPLIES 25
Message 2 of 26

Have you actually went in to Drawing Settings and made sure it is set to US Survey Foot?



Todd Rogers
BIM Manager
Blog | Twitter | LinkedIn

Message 3 of 26
Sinc
in reply to: kkuecker-traffic

We've had repeated problems with Microstation DGNs that convert to C3D using the wrong foot.  The very confusing thing is that we can get DGNs converted to DWG by someone like the Army Corps, and half of the drawings use the correct foot, while the other half use the wrong foot.  So I have to scale some drawings by that 1:2,000,000 factor, while others I can use straight as they come.

 

I have no idea why this would happen.  But many things Microstation still confuse me.  I hear that's a common problem with people who start out as AutoCAD experts, then try using Microstation (and the opposite also applies).

Sinc
Message 4 of 26

Yes we have.

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Message 5 of 26
wfberry
in reply to: kkuecker-traffic

I made note yesterday (2-7-2012) in another post in this newsgroup that  I had imported 2 dgn's into my dwt. that I had setup for US Feet.  I imported these KYDOT files and saved them and noticed that my settings were referencing International feet.  It has been years since the last time I had done that.  As far as I know we never use International feet here in Kentucky.  I was thinking that perhaps there was something in the dgn, but I do not think so.  This is Civil 3D 2012.

 

Bill

 

 

Message 6 of 26

Acutally, the same shift occurs if we designate the the C3D coordinates or not.

 

I have checked the DGN andthe file is indeed in the correct coordinates.

 

The issues seems to be with AutoCAD.

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Message 7 of 26

Have you tried doing a MAPIMPORT instead of attaching it?



Todd Rogers
BIM Manager
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Message 8 of 26

I could not use MAPIINSERT because the file I need to attach is a DGN - not an image

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Message 9 of 26

Not MAPIINSERT, MAPIMPORT.



Todd Rogers
BIM Manager
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Message 10 of 26

Yes - MAPIMPORT did the trick.

 

The troubleing thing now is - how much of our work done in the last four months is now shifted?

 

AutoCAD should not even allow an option for attaching a DGN as a reference if it will only be coordinatly correct using MAPIMPORT.

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Message 11 of 26

Usually when drawings, images, pdf's, etc. are attached, and they shift, it has to do with being to far away from the origin point, which is 0,0,0.  This is what they call a Large Coordinate Issue.

 

The accuracy drops the further away from the origin objects are drawn.  They can easily be off by inches or feet when far away.  The attachment origin may still be near 0,0, but the attachment objects are far away, and it shifts the file.  Large Coordinate issues come into play when objects are past 5000 units from origin.  If the drawing units are in inches, and objects are beyond 416 feet, they are beyond the limits.  The ending result is the attachment being off.

 



Todd Rogers
BIM Manager
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Message 12 of 26

YAYAYAYAYAYA....Live Action X



Todd Rogers
BIM Manager
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Message 13 of 26

Do you realize that is a totally unaccaptable reponse????

 

We bought this software thinking that it is capable of doing Transportation design.  Our distance from the 0,0 mark is always going to be a great distance.

 

the point we were questioning was at X= 244559.68, Y=570888.28.  The linear distance from 0,0 is then 621,065.91 ft or 117.63 miles from 0,0.

 

The difference between one International Foot equals 0.999998 U.S. Survey Feet exactly.  So the 621,065.91*.000002 equals a 1.24 foot shift. 

 

If we import MicroStation files into AutoCAD we have a 1.24 shift if we do not use the MAPIMPORT command.  1.24 feet is A HUGE DIFFERENCE!!!!!

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Message 14 of 26

This issue doesn't have anything to do with International feet and US Survey foot.  It has to do with the Large Coordinate Issue.  There is a good article on this at the link below....

 

http://www.cadalyst.com/aec/tip-autocad039s-big-problem-3383



Todd Rogers
BIM Manager
Blog | Twitter | LinkedIn

Message 15 of 26

Actually it is both a conversion and large coordinate issue.  That 0.000002 difference between US Survey and International over millions of "feet" equates to 1 or 2 (or even 3) feet off. We have had imports off by as much as 2.75'

 

Bottom line, MAPIMPORT is the only way to insure that it is doing an accurate conversion/import.  We have seen this mostly on DGN imports, but also on our Trimble GPS imports that we forget to set to US Survey Foot.

 

That is a good article because it does address issues like hatches and certain other commands.  But in the office here we have proven (unfortunately, time and again) that it is a conversion issue when it comes to points.  .0002% over millions of feet gets big pretty darn quick.

 

My 2 cents, for what it's worth.

Tony Leggieri
Gutschick, Little & Weber, P.A. (GLW)
CADD Manager
Civil 3D 2023.2.1
Windows 10
Message 16 of 26

i  have never experience that problem. but its seems like to me is that the dgn file is the problem. the micorstation file has be convert to the dwg format correctly before it will work correctly. this is something i have done many times without any problems. generaly microstations works in international xy system and when you are in civil 3d you can actually set the state plane system you are using and believe it or not there is a difference. i would think the problem is in the setup of the dgn file i bet its set to internation foot and not u.s. foot. i did this very same thing this morning and and worked perfectly.

Message 17 of 26
Sinc
in reply to: jmatte2004

I, too, feel this is a problem in the DGN setup.  Like I said, we can have the Corps use Microstation to create DWG files for us (no C3D involved), and we'll get inconsistent results.  It's always seemed like an error somewhere on the Microstation side.  I'm just mightily confused as to why we notice the problem once they convert the files to DWG, while they don't seem to notice the problem while working in the DGNs.

Sinc
Message 18 of 26

The problem is on both MicroStation and AutoCAD. 

 

We found that MicroStation has a setting in the export process for either feet or survey feet.  If survey feet is not selected in the settings of the seed file, the export will be shifted by .000002.

 

However, AutoCAD has a setting hidden away for the reference attach of DGN's that automatically puts it in International feet. 

 

Unless you use MAPIMPORT for a straight DGN

OR

a correct seed file to export a DWG to DGN

 

IT WILL NOT ATTACH PROPERLY.

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Message 19 of 26

That's good to know, being that I am not a Bentley user.



Todd Rogers
BIM Manager
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Message 20 of 26

One thing is the problem that any command that is vanilla AutoCAD based will not deal with Survey Feet. Only Map and Civil know the difference. You see this in you have your insert units set and try to Insert a drawing done in meters in to a drawing that is in Survey Feet. The insert command will convert Meters to International Feet only.

 

It may be time for Autodesk to think of issuing a special build of AutoCAD for Civil 3D. There are Map 3D commands that are disabled in Civil 3D because they will muck up the units. AutoCAD built for Civil 3D should be able to handle Survey Feet!

 

Allen



Allen Jessup
Engineering Specialist / CAD Manager

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