Friday, April 03, 2015

Survey Point

In my view, it is no accident that the Survey Point (SP) is named using Survey. It's purpose or role in Revit is to permit us to relate our project to survey coordinate data, which is ordinarily provided by linking an external file. This image depicts a linked DWG site file whose origin is roughly 85 miles from the southwest property corner. The iron pipe at this corner has X/Y coordinates of exactly 450,000',450,000'.

It was imported using Positioning: Auto - Center to Center. This is what Autodesk recommends we do with files that are far from origin. Place the survey information close to the Project Base Point (origin) of the project. Then I used the Acquire Coordinates (AC) tool which was created to let us PULL this information in from the external (linked) source.

After using AC the Survey Point (clipped) marks (makes it easy to see) the actual origin of the source survey data's origin. It is why it usually disappears off into the distance, in stark contrast to where the project's origin is.

When the SP is un-clipped and dragged away from the origin, presumably closer to the project's site, it begins showing coordinate values that equal its offset from its origin, the origin is not altered/moved.

This is what the project looks like after I've finished adjusting the position of the unclipped Survey Point. At this point I only regard it as a marker that validates my belief that my Revit project is now aware of the same coordinate values as, and aligned (in sync with), the linked Survey file.

At this stage I save the file as my Master Site file. This file will act as the Control for site relationships with the site for any and all related building files I may use for this project.

Next (in a follow up post):
  • Import a building file
  • Position it (X/Y)
  • Orient it (rotation)
  • Raise it to the appropriate Ground Floor elevation
  • Publish Coordinates
  • Repeat for other buildings

  • I'm intentionally NOT interested in the Project Base Point in this post
  • I intentionally did NOT move or alter the Project Base Point
  • I WON'T move or alter the Project Base Point in this file EVER.
  • I WILL turn off the visibility of the Project Base Point.
  • Shared Coordinates are NOT a Band-Aid, to fix poor communication/alignment


Unknown said...

In the "NEXT" step, you are recommending to publish coordinates to the linked building models. However, I am interested in understanding why you would suggesting such an approach as you know Publish Coordinates will create a file-to-file relationship that could make the files fragile... It works great if you look at it as different UCSs (Autocad term) that makes it easy to see various positions of the buildings, but how will you deal with the Shared Coordinates then?

I guess I am asking because we don't really want to establish such a relationship between Revit models in the first place. I'd like to know your thoughts on that. Thanks!

Ryan Taube said...

you mention that you Won't alter the Project base Point in the file EVER. Will doing so mess things up? or is the Project base point completely unnecessary in this file?

Barrie Sharp said...

Succinctly put. Lets hope people stop messing with the PB and start linking consultant models origin to origin.

Steve said...

Moving the PBP "clipped" in Master Site will shift the Survey Point relationship to the PBP, so will mess things up.

If the PBP is moved "un-clipped" it won't harm the relationship to the Survey Point.

Anonymous said...

What would be the reason for the stuff to turn sideways in some models (not all) when acquiring coordinates from a linked CAD (not to mention that the CAD file is the same for all of the models)? AC was done in the site plan view which is set to True North.

Steve said...

I find some CAD files and Property Lines will rotate when Acquire Coordinates is used after they've been created or Rotate Project North is used. I assume its because they are more or less regarded as "annotation" in the view. If it happens I just rotate them back by the same amount.

Anonymous said...

Great. Thanks!