Georeferencing after scanning

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gordonired
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Georeferencing after scanning

Post by gordonired » Thu Apr 12, 2018 11:41 pm

Hi everyone, I have a question for those of you working with total stations/georeferencing equipment in tandem with laser scanning. We have finished a scan for a client, and were provided a small list of survey points. These points were not taken on surveying targets, but rather on the equipment and general landmarks as a preliminary survey.

We don't have access to the surveyor who performed the work, and since it's so general in what was targeted (such as 4 corners of a concrete pad), it would not help us much.

My concern is how can I align my registered point cloud with this survey data? I have converted the survey points into a small pointcloud, and roughly aligned my cloud to it. We have access to Scene 5.4, Recap Pro and Infipoints (Elysium). Do you just line the cloud up and hope it looks good? Is there some magical software suite that can align our cloud to these dozen or some random points?

Yes we can always go back on site, and do it over again with proper surveying targets and scan them and match everything up, but that would involve a fair bit of work. Everyone prefers the cheaper method, and I for one have learned my lesson.

shahsaur90
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Re: Georeferencing after scanning

Post by shahsaur90 » Fri Apr 13, 2018 7:24 am

Hi,
You can use CloudCompare(Open source) for this.

The process is defined in the link given below:

youtu.be/S32wy66e_0o
https://www.youtube.com/watch?v=S32wy66e_0o

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Re: Georeferencing after scanning

Post by Jamesrye » Fri Apr 13, 2018 9:03 am

I guess it depends on what accuracy you need - how big the survey area is and if scale factor is an issue.

If the existing list of points is well spread through the survey area, then you could try to identify them in the point cloud and create 'virtual targets''. You could then register to these points and see what the residuals are. We use Cyclone, but I guess you can do this in SCENE? You mentioned a concrete pad, it should be easy enough to identify the corners from the scan data - especially if the surveyor recorded the top of the pad, then you can create the 'virtual target' to register to.

Alternatively, you could return to site and do a scan - in which you have two targets setup over coordinated points. You could do two or more of these scans depending on the size of the survey area. You can then cloud register your existing uncoordinated data to those scans.

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Re: Georeferencing after scanning

Post by pbashiri » Sun Apr 15, 2018 11:43 pm

If you have access to the job site, you can setup a vertical target on several survey points scattered along the site( remember to measure the vertical offset from target center to the ground) and do some quick scans (3 or 4 would be enough) then register them to your old registered point cloud.
Now you have your survey points in your point cloud. now you can register all your points against the survey points.

I`m in Vancouver, give me a shout if you need assistance.

Peyman

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