Compare As Built Point Cloud to Drawings

[Anonymous]

I am looking for a workflow for comparing as built point clouds with drawings, both 2d and 3d, in either Revit, Autocad, Navisworks, etc.

[Alfred.NESWADBA]

Hi,

part of our CAFM system can show comparisons between reality (point clouds) and planed situation (3D geometry like DWG, IFC, ...), the point cloud is colored then in ranges from green (close to plan) to red (most away from planned situation). This can be used to simply measure and visualize differences up to identifying objects added to the room or removed from the room and so beeing part of either plan or point cloud, but not both.

The only handicap maybe is that the software is currently available only in German, plans to translate to English exist, but no exact time frame for now.

If you are interested then please send me a private message with your email address.

- alfred -

[Anonymous]

Open the CAD file in Navisworks. Append the scan file (RCP/RCS) to it. If a 3rd party scan, then they should/could orient the provided scan to the project. Take measurements as needed in Navis from individual points to nodes, and/or run clash detection to find hot spots.

[JamesMaeding]

nice. I never tried pt clouds in navisworks but its great.

If only it did not have the rcs requirement. Why oh why does adesk not bring back the .las and .laz reader?

[dgorsman]

---

@JamesMaeding wrote:

nice. I never tried pt clouds in navisworks but its great.

If only it did not have the rcs requirement. Why oh why does adesk not bring back the .las and .laz reader?

---

Because every product team was doing their own thing; AutoCAD users didn't have the point cloud tools/readers that Civil3D did, Navisworks had something else.  Putting all the development in one silo makes sense overall, although civil users ended up on the losing side.  So now there is only *one* LAS/LAZ (and all the other supported formats) reader that needs to be maintained, inside one product.

As for the OP, the method of comparison depends on *what* you are comparing.  If this is for buildings (since Revit was mentioned) then it's best to do a visual inspection in Navisworks or Revit.  Alternatively, you could compare in ReCap by bringing in an NWD file.  For mechanical design, where small objects are scanned in high detail, it would make more sense to mesh the result and then compare inside Inventor or other similar program.

Comparing point clouds to 2D doesn't make much sense.

[JamesMaeding]

I'm just loving ReCap so much too. Its got the interface of a touch screen soda vending machine but at least those do not spam me with "buy the full version as this one will expire" when it really does not expire. Autodesk has good ideas, but they package them so bad these days.

[Anonymous]

Thanks all. On one project, I only have 2d .dwg files from the architect. This is for a small 20k sqft project. They’ve asked for an as built point cloud comparison, but the .dwg files aren’t georeferenced, and so I can’t figure out how to provide the same origin point to get the files to match up. I was thinking of creating an orthophoto to match up with the different drawings, but it almost seems faster to convert the 2d drawings into 3d, georeference them myself, provide the origin point, and then do the comparison. Thoughts?

[dgorsman]

When you get point clouds for design use, *always* request them to be converted to your project coordinates.  You'll need to provide several locations that are easy to find in the point cloud along with the coordinates you want them at.  I've seen as few as 3 and as many as 8 points needed; more points and further apart means less overall error.  Don't worry about survey coordinates, use values that make sense to your project i.e. close to the WCS origin, not waaaaaay out in space, and lined up nicely with the X and Y axes rather than true north.  That way you can bring the point cloud in as-is without any buggering about.

[hadleyRJHEH]

Hi Alfred.

Read your post and we are also looking for an off the shelf solution to compare DWG to point cloud where we can set our thresholds for compliance.  We do not speak German 🙂

Do you have any solutions you know of?

Thank you .

Hadley

[JamesMaeding]

@hadleyRJHEH 

Look into cloud compare, its free.

I found this post on pulling in dxf, though its related to the coord shift CC can do:

https://www.danielgm.net/cc/forum/viewtopic.php?t=1150

You will likely have to choose some "base point" you line up the pt cloud and 3d linework with.

Maybe rotation too.

CC is pretty powerful, you can "segment" pt clouds, meaning chop them up to clean them, and several other things. I use TBC mainly to manipulate pt clouds, but it cannot align them to anything once past processing if you use that.

thx

[autoid374ceb4990]

@JamesMaeding wrote:

nice. I never tried pt clouds in navisworks but its great.

If only it did not have the rcs requirement. Why oh why does adesk not bring back the .las and .laz reader?

Could you (or anyone) post an example of an .LAS file?  My reason for asking is that way back in R14 I wrote an ARX program to read LAS files into AutoCAD.  Just wondering if it still works with what you "new guys" are using. 

Thanks,

Charles

[JamesMaeding]

@autoid374ceb4990 

I have .net code to read and write .las/.laz, so the interesting thing is what entity you created in acad using your tool. Surely not points. We are talking 100million plus pts so that will constipate cad.

[autoid374ceb4990]

Yes I was creating AutoCAD POINTs and you are correct,  R14 on 32 bit Windows XP and about 4,000,000 points and you are out of heap space.  I  was reading LIDAR data and creating contour maps, so I built in a filter so I could read every other point, or every 3rd point, or every 4th, point etc.  Luckily the structure of the LIDAR file made the filtering easy and the results were very accurate when compared with "on the ground" measurements.

So you are not creating POINTs?