Dimensional Control / Antenna installations

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marky9074
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Full Name: Mark Payne
Company Details: Blue Ocean Seismic Services
Company Position Title: Survey Project Manager
Country: United Kingdom

Dimensional Control / Antenna installations

Post by marky9074 »

Hi there,

First post! I'm currently working for a start up in underwater autonomy and during our development phase are chartering vessels of opportunity as and when we need them (for example a PSV last year for one trial off Aberdeen).

Typically all our equipment is containerised and we have built an antenna platform that lifts on top of a container so that we are 100% independent of the vessel's positioning and reference system. To that end, we have to establish some basics.
  1. Vessel heading
  2. Antenna offsets relative to a common reference point (CRP)
  3. Relative position of an over the side equipment pole
On a small vessel (survey catamaran) this has been done by tape and just accept the error. For larger vessels we have started to pull in a contractor to perform a dimensional control survey at great cost (considering the limited number of points to be surveyed).

As most of the antennas to be defined are attached to GNSS receivers that can be set to log data, it is possible to process the RINEX either by PPP online or by various other means to get quite accurate control. The issue we have is then linking this established control to other points, for example an over the side pole.

We dabbled with an iPhone 14 Pro last year and had high hopes for a low cost solution using the LIDAR sensor, but soon noted that we managed to get a clean scan of pretty much every feature of the vessel bar the antenna poles and antennas themselves!

Following this, we started looking at target spheres and so far have not found a low cost one with a 5/8" thread top and bottom that we could put in-between the antennas and other features and leave in place. I did find these, but too expensive for testing:
https://www.scan-eye.com/online-store/S ... -p74934652

The objective of this post is to find something similar with 5/8" UNC threads top and bottom that is 3D printed or available to buy that is not prohibitively expensive. I also need some guidance on best practice/software that will compute the centre of the sphere and align point clouds based on the spheres so that I can then manually georeference them and then calculate relative offsets.

Any suggestions for the next step up to a handheld scanner would also be welcome.

Any help would be much appreciated.
marky9074
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Joined: Mon Nov 20, 2023 1:26 pm
Full Name: Mark Payne
Company Details: Blue Ocean Seismic Services
Company Position Title: Survey Project Manager
Country: United Kingdom

Re: Dimensional Control / Antenna installations

Post by marky9074 »

Just to update. Have received some sphere targets from ever helpful Tad @ Koppa Targets and hope to do some more testing next week. Am also looking at the Pix4D suite of tools which I think will provide a workflow that will address what I am trying to accomplish. Will report back on my progress.
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Re: Dimensional Control / Antenna installations

Post by Martin_au »

Is laser scanning a bit of overkill for this? Would a total station with reflectorless capability be sufficient? Just setup somewhere where you can see everything, turn off the compensator, shoot the poles/antennas and apply a suitable length offset for each point.
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