Thursday, February 26, 2015

Toposurface from a Text File

I responded to a thread at the Autodesk Community Revit Forums back in May. They described having a survey file and a points file that could be used to create a toposurface. My initial reply focused on resolving this warning, "Imported Toposurface Points are located a large distance from the model and might not display properly. Points will be centered on the model instead".

I offered this advice.
  • Import the survey (a DWG file) first using Auto - Center to Center
  • Move it so the relevant portion of the site is roughly centered on the Project Base Point/Survey Point
  • Select the Survey Point and Unclip it (this prevents it from moving to the 0,0,0 location of the DWG file in the next step, which is far away)
  • Acquire Coordinates from the DWG survey file
This resolves the real world coordinates based on the survey data. I felt they'd be able to create the toposurface successfully. Instead, they responded that the toposurface was not created in the correct location. I took another look and experimented with the points file they posted (in the thread) and offered these steps.
  • Add a new set of point coordinates to your text file at 0,0,0, on the first line.
  • Use this version of the points file to create the surface.
I then commented, "If you followed my directions earlier about acquiring coordinates you should see the coordinate values of the survey file when you select the Survey Point.". Then I recommended the following steps.
  • Unclip the Survey Point > Enter E/W: 0' and N/S: 0'
  • The Survey Point should jump to the 0,0,0 location of the survey file, far from the project origin.
  • Make sure your View Range is set high enough to see all the points of the surface
  • Now create your toposurface
  • When the points are visible you'll see one point at 0,0,0 but it will be at the Internal Origin (>R2020, Project Base Point in older versions)
  • Select all the (toposurface) points > move using the Internal Origin/Project Base Point location as your first pick and the Survey Point as your second pick (see image below).
  • This will move all the points down so the toposurface is located properly relative to the survey
  • Before finishing the surface > Delete the one toposurface point at 0,0,0
  • Finish Surface
I found that adding the extra point at 0,0,0 silences the warning about the distance from origin and it gives us a known location within the point data to select and move the entire surface accurately.

Then another member asked about doing something similar but wanted to report a project elevation of 100'-0" instead of 0'-0". I replied with the following.

In order to show the Project Elevation as 100'-0" you'll need to model your building at that project elevation instead of 0'-0". Then when you establish shared coordinates you can show the true elevation. If I was tackling this I'd create a building model at 100' and a separate "site" model.

I'd import the site data in the site model and create a toposurface. It should be at the real elevation and report the relevant coordinates you expect. Then I'd import the building into the site model, move it into position X/Y, rotate it if necessary into alignment with the site conditions and finally move it up to the intended ground floor elevation. Then I'd use Publish Coordinates to pass the building position information out to the building file.

When you open the building model you can edit the Level parameter Elevation Base to use Survey Point (versus Project Base Point) and it will show the True site elevation values instead.

Just a couple days in the life of a thread at an online user forum (spanning nine months).

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