AutoCAD Map 3D General Discussion

AutoCAD Map 3D General Discussion

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Member
remyyyT
Posts: 4
Registered: ‎05-10-2012
Message 1 of 8 (774 Views)

How to georeference a .shp from a .dwg non georeferenced?

774 Views, 7 Replies
05-10-2012 06:56 AM

Hi,

I'm new in Autocad Map 3D (and Autocad also). I have a .dwg non georefenced and I'm able to have the longitude/latitude of several points of this .dwg. I work with the trial version of Autocad Map 3D 2011. My aim is to get .shp georeferenced.

For the moment, I assigned a coordinate system (LL84) to the .dwg. After that, I don't really know how to georeference my .dwg with the latitudes/longitudes that I know.

To convert .dwg to .shp, I think it's ok. I already did some tests (.dwg->.sdf->.shp). My problem is georeferencing.

I will greatly appreciate any help.   Thanks

Remy

Mentor
tjmapper
Posts: 229
Registered: ‎03-25-2008
Message 2 of 8 (771 Views)

Re: How to georeference a .shp from a .dwg non georeferenced?

05-10-2012 08:08 AM in reply to: remyyyT

You can find the button or use the command 'MAPCSASSIGN' to assign a coordinate system to your DWG. When converting from DWG to SDF or SHP you can define what coordinate system you are exporting it too on the 3rd tab of the export dialogue.

 

When you add something from an FDO connection it will automatically assign the coordinate system or the source if the drawing does not already have one defined.

Member
remyyyT
Posts: 4
Registered: ‎05-10-2012
Message 3 of 8 (769 Views)

Re: How to georeference a .shp from a .dwg non georeferenced?

05-10-2012 08:14 AM in reply to: tjmapper

Thanks for your answer. Nevertheless, I have no problem to assign a coordinate system to my .dwg.

 

My problem is to georeference my .dwg with several points for which I know their longitutde/latitude.

Mentor
tjmapper
Posts: 229
Registered: ‎03-25-2008
Message 4 of 8 (766 Views)

Re: How to georeference a .shp from a .dwg non georeferenced?

05-10-2012 08:36 AM in reply to: remyyyT

So you just want to insert your points using Lat/Long in the LL84 coordinate system?

 

or you have a set of shapes/points (parcels, survey points) your trying to move to those coordinates??

 

If you are inserting points at a Lat/Long and your drawing is in LL84, all you have to do is set your insertion point to your Lat/Long. 'POINT' command then type '-84.23165,36.564984' (your coordinates)

 

if you are trying to move a set of shapes/pointes to certain coordinates you can move them using a known basepoint to the proper coordinates. If it doesn't fit there is a rubbersheet command.

 

Is it a drawing you received and are trying to assign coordinates too? Or something your making from scratch?

 

Sorry for a the vague response, but there are a lot of details needed to answer a question that has 100 answers.

Member
remyyyT
Posts: 4
Registered: ‎05-10-2012
Message 5 of 8 (760 Views)

Re: How to georeference a .shp from a .dwg non georeferenced?

05-10-2012 09:07 AM in reply to: tjmapper

Sorry for my vague question. I can try to detail.

I received a .dwg which represents a "little city". This .dwg is not georeferenced and for my application I need .shp georeferenced of this .dwg.

I assigned the .dwg to the LL84 system coordinates. But for the moment when I use the track coordinates for example, my top of my .dwg is X around 59000000 and Y around 13000000. So, II would like that this top point be X around 48,7 and Y around 2,2 (because I know that this point have longitude 48,7 and latitude 2,2).

In fact I would like associate the real longitude/latitude of several points (instead of the original coordinates kind of X -> 59000000 and Y -> 13000000). To my mind, this operation would permit to georeference my .dwg. Maybe it's a mistake.


I hope to be clearer..

Mentor
tjmapper
Posts: 229
Registered: ‎03-25-2008
Message 6 of 8 (758 Views)

Re: How to georeference a .shp from a .dwg non georeferenced?

05-10-2012 09:14 AM in reply to: remyyyT

That's exactly the information needed to asnwer your question.

 

Unfortunatly you probably won't like the answer.

 

It sounds like the drawing you were given was drawn in a coordinate system that was not translated to the DWG. So you have more than just XY problems. The scale is probably way off. So unless you can find out what coordinate system it was drawn in, the best hope you have is using the rubbersheet tool.

 

Here is a link to a video on how to rubber sheet.

 

http://docs.autodesk.com/MAP/2013/ENU/index.html?query=georeference

 

That is all that I would know to do, but maybe someone else can give you better answer if there is one.

Member
remyyyT
Posts: 4
Registered: ‎05-10-2012
Message 7 of 8 (756 Views)

Re: How to georeference a .shp from a .dwg non georeferenced?

05-10-2012 09:20 AM in reply to: tjmapper

Thank you for your quick response

Valued Mentor
parkr4st
Posts: 475
Registered: ‎03-24-2004
Message 8 of 8 (745 Views)

Re: How to georeference a .shp from a .dwg non georeferenced?

05-10-2012 11:48 AM in reply to: remyyyT

other stuff to try that may help

 

find a geo-referenced aerial photo or topo map of the site and put you points over that.  Lets you know if you are "reasonable in you location".  You may spot some of your points in the photo ie road intersections, manhole covers, fire hydrants, etc that you can tie your points to increasing the accuracy of your data location.

 

GPS or other point data gathered on the site on the ground are even better as it will allow better precision.

 

The other thing to keep in mnd is the needed accuracy and precision for the project.  close may be good enough, within a m better, within a cm even better or necessary.

 

Dave

 

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