Target placement for C2C geo-referencing

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jbronico
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Target placement for C2C geo-referencing

Post by jbronico »

Hello all. I'm using a P40 scanner and cyclone for registration. My typical workflow is field scan (collect targets in field), register in cyclone using c2c, take that registered cloud and register it with the "control" cloud which are traditionally located control points associated with each target. My dilemma comes into play here. It is agreed that we need a minimum of 3 targets per job, but our field crew got it in their head that all three targets must be within 75 feet of the scanner and visible from the same scan. This leads to all of our control for an entire site, sometimes up to an acre in size, being controlled by a 75' triangle. I think the targets should be spread out throughout the site. Usually trying to get each target in at least two scan setups. Some setups will have no targets, some have one, some have multiple. My thought is that since I'm only using the targets to tie to existing control, it is better to have them spaced out to reduce possible rotational errors. All of the individual scans are registered together by the time I do anything with the targets anyway, so in my mind that is making all the target in one scan like our crew wants, but they are dead set that the sales rep told them all three had to be in one scan during training, so they refuse to consider my second thought process. Maybe neither of these methods is the best way and one of you have a better method. I'm open to all comments as I am trying to use the best methods possible to create a better end product.

Thanks in advance
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Re: Target placement for C2C geo-referencing

Post by badam »

As you would do, the targets should be spread over the surveyed area, and not a requirement to be seen from one location.
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Re: Target placement for C2C geo-referencing

Post by JNally »

Badam is spot on with that. on a long job having survey control only at the start is dangerous. You will likely have drift by the last scan.
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Re: Target placement for C2C geo-referencing

Post by christopherbyrne18 »

Solely using C2C for aligning the scans and block shifting it to control targets is also dodgy....

At a minimum every other scans shoul have 3 or more targets controlled by total station to minimise error propogation.

Using C2C for long runs without control is not good.
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Re: Target placement for C2C geo-referencing

Post by 6R07K »

G'day,

Going to assume from your comments the environment is suitable for C2C based on what you are trying to achieve. That being the case best to space the targets for georeferencing around the site. In its simplest form I would still recommend more then 3 for redundancy and consideration given to the size of the site also.

My guess the lines got crossed and the three targets in one scan was for a target registration without C2C.
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