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.

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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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Re: GEOREFERENCING DURING SCANNING

Post by dhirota » Fri Apr 20, 2018 1:18 am

I do not know if this response is appropriate. We normally use targets for our scanning with our surveyors obtaining the location of the targets. We have decided to establish a GNSS network to reduce that expense of target acquisition especially in remote densely vegetated areas. We decided to use an established Trimble base station in HNL with a "borrowed" Trimble R10 sensor rather than one of our Trimble R8 on our Riegl VZ400i. The test project was the Lyon Arboretum at the end of the road of Manoa Valley for those that have visited the falls nearby.

4-15-2018 1-05-04 PM.jpg
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SP001_4-19-2018 11-24-02 AM.jpg
SP007_4-19-2018 11-26-47 AM.jpg

We scanned 11 scans on Friday and 12 on Sunday, each group taking about one hour. Each scan took 45 seconds producing approximately 22 M points and the 7 images from the 36Mpixel Nikon D-810 took an additional 60 seconds to capture. The total number of points for the scans is about 285M.

The two days of scans were merged together using Riegl RiSOLVE software and the course registration in the field with the better GNSS positions (Fixed RTK positions of the Trimble R10) were locked using Riegl MSA (multi-station adjustment) and the floating RTK scan positions (there were several because of the trees, 70 feet tall) were adjusted to the fixed positions.

We are still learning and have not checked everything out completely, but I think time and accuracy will improve.

PS. forgot to mention all the flooding in Hawaii for the last week. The interesting thing about these scans was the rain and the wind moving at 35 to 40 mph, so nothing was standing still. My 200 foot driveway, 20 feet wide had 4 inches of water, running down to my neighbors at 3 to 4 inches per hour for several hours. At the bottom of our hill, the 6 lane divided highway next to the beach had 2 feet of water running over it.
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Re: GEOREFERENCING DURING SCANNING

Post by dhirota » Tue Apr 24, 2018 7:16 pm

We received some excellent help from Riegl support to translate the "undocumented tips and tricks" of RiSOLVE to deal with a remote project site with rain.

1. 04-23-2018 04-49-29 PM.jpg

Total 19 scans on two rainy days, approximately 1+ hour per day because of time constraints and rain. Used Riegl VZ400i + Trimble R10 in RTK mode + Nikon D-810 with 20mm lens. In the field, for each scan position, scan time 45 seconds for approximately 22M measured points, range 250meters, followed by photography time of 60 seconds, 7 images at 36 Mpixels each.

2. 4-23-2018 4-24-37 PM.jpg

Office time was less than 1 hour, including 20 minutes to colorize scans positions (approximately 1 minute per scan), registration (registered in the field), detailed registration adjustment using Riegl Multi-Station Adjustment, Riegl Project generation, Color panorama photograph and panorama color scan generation for RiPANO visualization. Total 233M points used in final project data set.

3. 4-23-2018 4-40-47 PM.jpg

4. 4-23-2018 4-43-59 PM.jpg

5. 4-23-2018 4-44-38 PM.jpg
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Re: Georeferencing after scanning

Post by DanielNMP87 » Tue Apr 24, 2018 10:24 pm

Hello,

I'm late to this party but...have you tried to pull the RCP in position in AutoCAD? You just need the Topo and some points on something to drag it roughly in the right place...

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Re: GEOREFERENCING DURING SCANNING

Post by dhirota » Sat Apr 28, 2018 7:58 pm

This is the last of this project example, illustrating the use of Riegl RiPANO for visualization, measurement, and easy transport to multiple platforms including PC, MAC, iOS and Android using the geospatial reference obtained during scanning without the use of targets.

4-28-2018 8-38-47 AM.jpg

4-28-2018 8-14-44 AM.jpg

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