Shared Co-Ordinates

[benmay]

I am starting a new project and have been going through the process of setting up my site model. Its a reasonable size site about 200m long and 100m deep.

I am working on the Structural drawings (don't hold that against me) and am linking in architectural and survey drawings in DWG format.

I just cant seem to get the shared co-ordinates working

This is what I am doing so far;

-setup of site file with site DWG file linked centre-to-centre
-Acquire Co-Ordinates of site file
-Save etc

I am basically working to Wes's tip here http://forums.augi.com/showthread.php?p=718797#post718797

Then when I link in the next drawing with shared co-ordinates checked to the same World Co-Ordinates system it doesn't bring in the drawing correctly.

And it also isn't exporting the linked drawing to the acquired Coordinates

Am I missing something here, is there something else I am forgetting to do?

[benmay]

I think I just solved the problem (after numerous hours of head scratching)

I believe it was the issue with the survey being more than 1.7km from the 0,0 point, but by drawing a line in the survey drawing at 0,0,0 to the centre of the survey accquire points works

I made sure that the survey was linked in at 0,0,0 at the centre, meaning the revit co-ordinates are not outside the 1.7km circle

now my shared co-ordinates are correct

does anyone know if I will have problems with setting up the shared co-ordinates to these values? My shared co-ordinates are in the nine figure range

[sbrown]

Revit doesn't like numbers outside of 2 miles away from the origin. Graphic issues can occur. If you notice hatch patterns(revit patterns) not displaying properly or dwg lines looking squiggly this is due to objects far from 0,0,0. Exporting should be fine(make sure upon export you check the pull down and switch from internal to shared).

Anytime this issue comes up revit recommends you move your dwg data closer to 0,0, before linking to revit. This is not always practical but is what they tell you to do.

[David Conant]

This method should ALWAYS be followed. It is critical to follow when the survey coordinates of your building site have large values (> 2 miles/3km from site 0,0):

ALWAYS locate sites underneath buildings. Revit buildings like to stay near home and be oriented to project north. Sites can wander about and talk to the buildings later. DON'T try to pan your view 40 km northeast of 0,0 and try to build your building model there because your site coordinates have a remote origin. This will work in AutoCAD but in Revit you will be very unhappy.

NEVER import or link a site with large coordinate values Origin to Origin! This may seem correct based on AutoCAD experience, but here too you will be very unhappy in Revit. You will get the correct origin later in the process.

Build your revit model at or near the position of the elevation marks in the default template with the building oriented orthagonal to your desired printing frame. i.e. use a Project North not True North for your working environment.For one building on a site:

Link in a site model or site dwg.
Move and Rotate the SITE so that it is located correctly relative to the building.
Acquire the site's coordinates. Now, the site's origin will be the origin of your shared coordinates. The site's Y axis will be True North. The site coordinate values can be arbitrarily large without disturbing Revit's internal calculations.
You can later open the site model and link in the building using shared location and it will land in the exact position.For multiple buildings on a site:

Create a Site project, link in a site dwg, placing the center of the building site near the center of the default view.
Acquire coordinates from the site.
Build any site elements, topos, etc.
Link in building rvts. Move and rotate them so that they are correctly located on the site.
Publish coordinates to the rvts. Now all models will have the same Shared origin and True North orientations.
You can now link the site into any of the buildings (the other buildings can be linked in as well) using shared location and it will be in the exact location.

[benmay]

Thanks for both you replies, you basically confirmed what I was thinking.

Just to clarify though, once I have created my model and acquired co-ordinates, my co-ordinates are actually based on the linked site DWG, my understanding here is that these are the shared co-ordinates? And Revit is still using the project co-ordinates for its database?

This method certainly works better for exporting drawings where you would have been exporting then running a script in ACAD to relocate the project.

[patricks]

Reading up on this subject and had a question: I have a CAD survey which lists a couple of control points on the site, with Northing and Easting values. The Northing value is around 3500 feet and Easting is around 5300 feet (more than a mile), and that is where the CAD elements are actually placed in relationship to the 0,0,0 origin. So that puts the general center of the CAD file around 7200 feet from origin. Do I need to move anything in the CAD file before linking it into my project, or can I just go ahead and place it center-to-center?

Also, what do everyone do when they are dealing with a messy CAD file with annotations and other artifacts all over the place in the Z-direction? I have one with notes and annotations at ~500 feet negative, ~1000 feet negative, some things at 0, and then the contours and some other things at the correct elevation, ~250 positive in the Z-direction. So if I link it in center-to-center, the actual contours end up at some arbitrary dimension nearly 1000 feet above my building.

[benmay]

I have just been through the same questions you are asking so I can at least tell you how I go about this.

First cleaning up the survey file, I never link in a survey file straight from the surveyor, First thing I do is take the 3D survey and create a copy and store it somewhere in the project directory that will be safe (generally the survey shouldnt change throughout the job)

I will then either freeze unwanted items such as text and symbols (if the layering system is good, otherwise I will either change to a freezed layer\delete from the file if there is a lot of junk. Then you need to look at drawing in elevation and check there are not any funny entitys that are at the wrong elevation, again either delete these or change to a frozen layer. Now you should have a pretty clean file to link into Revit

Following the steps outlined previously you simply link the file centre to centre, but before you do that I find it useful to drawing a model line circle at 0,0 with a diameter of 2miles or 1.6k. (I have even seen a family floating around for this now, which is easier than g etting the model line at 0,0)

Now you can link centre to centre and move the linked drawing so it is roughly central in the circle you have drawn

Then you just need to accquire co-ordinates, and all further links (and exports) can be done via shared co-ordinates

Hope this is of some help

[Dave F.]

Hi
RS '08

I've followed the instructions given above (I think), but I'm still having problems.

Here's step by step of what I've done:

* I have a dwg site survey with the correct world co-ordinates.
* I link it into a new Revit project. Centre to centre
* I draw a few grid lines over the site plan.
* Acquire co-ordinates.
* Export to CAD formats (Dwg)
*I open up the dwg. The site survey is in the correct location but the grids (& elevation markers) are based aorunf 0,0.

What am I doing wrong.
All help would be gratefully received

Thanks
Dave F.

[LRaiz]

Did you select the option to output shared coordinates during export to dwg?

[Dave F.]

Yes.

Do I have to use 'specified co-ordintaes at point'?

[Dave F.]

OK, I stripped out all entities from the linked dwg except the basic grid (lines) & it worked fine.

So my next question is what entities would cause this?
Has anyone else had issues like this?

Thanks

[David Conant]

One common problem occurs when a survey file places the site at large coordinate values and at the same time has some entities created near 0,0. Even a few entities there creates a file with huge extents and can make Revit unhappy. Purging your file of extraneous elements may have removed such entities and thereby improved its behavior.

[scatter529359]

for some reason, no matter what i do, i can't acquire coordinates from my CAD file.

any ideas?

[scatter529359]

never mind. sorted.