Workflow for Survey Control P series instrument

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joel.hicks
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Workflow for Survey Control P series instrument

Post by joel.hicks » Tue Dec 03, 2019 4:41 am

Hi Forum,

can anyone share a basic workflow to capture survey data alongside laser scanning data?

We are working on a large civil site and would like to use the targets to capture them both by the scanner and then by the survey theodolite, import this data into cyclone.

Grateful for your help.

Joel

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Matt Young
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Re: Workflow for Survey Control P series instrument

Post by Matt Young » Tue Dec 03, 2019 7:39 am

Ideally you will want to start with a traditional survey traverse around or through your site to establish good control points on the ground. Be sure to process your traverse on a flat grid if GPS is involved. Laser scanning in general terms is on a flat grid. If you are scanning a very large area then you may want to break things up a bit. Then you can set up targets in the areas you are going to scan. These can be either paper targets or movable ones like tilt and turn checkerboards. Tie your targets into your control traverse by way of a resection or similar method as you carry out the scanning. If weather conditions are good and you use paper targets, you could survey them all before getting the scanner out of the box.

To summarise:

Good survey control network.

Good target placement and naming convention.

Scanning

In that order ;)
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Re: Workflow for Survey Control P series instrument

Post by mike annear » Tue Dec 03, 2019 8:26 am

Hi Joel,
I am Brisbane based, I can coordinate your project for you.
I am not a surveyor, but have lots of 3D scanning site experience working for surveying companies over the last 12 years.
Regards,
Mike
www.mikeannear.com.

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Re: Workflow for Survey Control P series instrument

Post by stutosney » Tue Dec 03, 2019 10:11 pm

+1 what Matt said. Also, if you want to coordinate a scan with a solid control network, use a surveyor and don't try to do it yourself. I lived and worked in Australia doing surveying and scanning,if you need any advice or want any contacts of someone who can come in and do your control, let me know.

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Re: Workflow for Survey Control P series instrument

Post by mstachoni » Wed Dec 04, 2019 5:51 pm

In addition to the previous comments, I would add the following comments and alternative workflow.

I'm a big fan of surveying targets by a licensed surveyor for applying control rather than trying to record the position of the scanner over a control point using the P-series survey capabilities. On construction sites your PK nail or X-cut in concrete will likely get destroyed or covered up with 1000 lbs of materials.

Using a licensed surveyor to do all survey control layout will be more accurate and a heck of a lot less trouble than trying to use the survey capabilities on a P-series scanner. You also need to record the instrument height which sucks up field time - it's way more of a pain than its worth. Use the scanner later to establish any "infill" control points which can be positioned by resection back to established survey control points.

Planned correctly, you may be able to get away with only a day's worth of a surveyor's time, but planning is critical.

My personal workflow is thus:

1. Before you do anything in the field, map out the site / project in CAD or BIM and establish a series of initial rough scanner setup locations, using a simple circle with a diameter of e.g. 60-80m to understand overlap and effective range for a P-series scanner. Take into account line of sight issues to targets, especially if planning for construction site scanning where things change daily.

2. Ensure the BIM or CAD plan is properly aligned to the Project Coordinate System, e.g. the local State Plane Coordinate System used to establish all future site coordinates.

3. Using this scanner positional layout, which is optimized for what needs to be scanned, to understand where targets should be optimally placed in the field in order to get the best overlap. Plan such that you have at least 3 targets visible per setup.

4. I HIGHLY recommend you place your initial targets such that they can be considered stationary and will not move for a foreseeable time. Every project is different but this initial layout can be critical downstream for making future target or C2C registration work easier. If this is an active construction site, where you place targets on day 1 may get demolished or moved on day 140 so you need to account for this. As construction progresses you can lay out targets where you could not before, so pre-planning is a critical component.

5. For this initial work I usually affix hard targets, printed on vinyl waterproof labels placed on painted 1/2" plywood, in the field using various methods, e.g. glued to hard walls using construction adhesive (or hot glue for interiors), 16ga wire tied to a fence, or otherwise mechanically fastened to some fixed element in the field. I've also used targets printed on magnetic sheet vinyl placed on structural steel with great effect. Paper targets placed outside will usually get destroyed by the weather within a month.

6. Record the coordinate positions of all initial planned rough scanner and target locations from the model/CAD. Using Point Layout or Trimble tools you can export coordinate points from your CAD/BIM application to a total station.

7. Work with your licensed surveyor to locate the targets and initial scanner setup positions in the field from the planning model, then have the surveyor record the actual field position of each target, and export these points to CSV. Back in CAD/BIM, import these points and position the targets accordingly for future planning purposes.

8. Scan from each of the setup positions as provided by the surveyor. The scanner setups can be simply marked with some spray paint and can generally be pretty rough - you just want to establish from the plan where the setup can see the most targets. The actual coordinate position of the scanner isn't really important as you are using targets and C2C for registration.

9. Obviously you can take more scans that originally planned if you find field conditions warrant and you can see enough targets or overlapping field elements to perform decent C2C registrations.

10. If you are scanning conditions which change over time, you should be able to keep building build additional scans which can be C2C'd back to previous scans which ultimately tie back to the original scans.

11. Every so often you should re-establish control with new targets as the opportunity arises.
- Matt

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Re: Workflow for Survey Control P series instrument

Post by steves01x » Thu Dec 05, 2019 12:29 pm

You have had some brilliant replies. I would add:

1) Check if you can get the team working on the civils project do your total station work so the exported control file is all exactly to their spec/requirements with their chosen kit (up to date calibration certificates) and their chosen software to process it etc. Its worth every penny to pay someone that has good kit, experience and insurance!

2) If you can work along side the team doing the control, make sure you use HDS targets as well as your paper ones - get the paper ones named sensibly in case you need to split the job up aka per floor etc as it may make life a bit easier in Cyclone if your on a monster project. The HDS ones to pick up easier and you can get them placed in locations paper targets are no use.

3) i have always found it quicker in field / smoother in Cyclone to have done 360 scans with no detail/window scans to collect targets.

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