Applying control in Cyclone core

[Ioannis]

I have to scan a 3 km road, anyone can remind me how to apply control network in Cyclone? I was thinking to spread some targets and measure them with total station. Then I insert in cyclone and press target Id constrains?

[Florentin.Drogeanu]

Hi Ioannis,

I think it depends on what are your accuracy requirements, what scanner you are using and how you coordinate your scans together. That would
But to put it lightly, yes, you just match the targets in your scans with the targets from your total station. You just need to put your coordinates in a text file with: Target ID, Easting, Northing, Height (or match the order in the import settings).
You import it in your project (comes up as a ScanWorld). In the Registration window you add the ScanWorld (with the imported control) and you set it as Home ScanWorld. Then auto find constrains.
A few things to remember:

• Make sure you use the same name if you want to easily auto-match targets. Cyclone is case-sensitive so T001 will not match t001.

• If you want to make changes to the scanned targets, do it in the Control Space. Any changes made in the Model Space won't affect registration.

• Take care of the heights used. If you determine the targets as ground control points either:
  • add the target height in Cyclone for each target
  • add it in the control calculations and use them as centre of targets

Hope this helps.
- Florentin

[Ioannis]

Yes I remember the procedure to insert the targets. The thing that I can not remember is the following. Let’s say we have 50 targets in our project with geodetic coordinates and insert them in cyclone. In the other hand we have the registration of the scan stations of the road that we have done c2c.
Let’s say the c2c has some cm drifts.
Τhen when I apply target id constrains Cyclone corrects the c2c registration as it keeps the 50 targets as a geodetic base? It’s like a traverse that we put trigonometric points in the end and some in the middle?
Let’s say Cyclone apply correction to the c2c registration when it has trigonometric points as a target or not?
And if yes how it done it as when I press registration with target Id constrains I see the drift of the c2c compared with targets.

[Florentin.Drogeanu]

Τhen when I apply target id constrains Cyclone corrects the c2c registration as it keeps the 50 targets as a geodetic base? It’s like a traverse that we put trigonometric points in the end and some in the middle?

The ScanWorld with the fixed control will not change geometry. It will be fixed. Your scans will move depending on how you do your registration. If you do a registration that contains everything (scans + control) then the scans will be corrected. On the other hand, if you do your local registration and save it in a separate ScanWorld, then you use this to match it to your control, the individual scans won't move.

This is how I would approach it:

Check quality of local registration
This will show you the differences between the geometry of your local registration control and your surveyed control network. It's also a good way to check for blunders in target naming.

• Do your local registration between scans and freeze it. Assuming you're happy with the quality of it.

• Create a new registration where you have just 2 ScanWorlds (the one containing your registration from point 1 and the one with your 50 control points)

• Take note of where these discrepancies happen as you can use it to optimise the registration in the next step. Do a visual check of the quality in these locations as well, to make sure the cloud constrains are fit for purpose.

This way you can see if and where you're out compared to the control points.

Adjust registration based on control
After you've done your initial check above, create a new registration, import the local registration into it and add the scan world containing your control as well and make set is as home ScanWorld. Use the notes taken before to adjust the Cloud to Cloud constrains. Your original registration won't get affected.

I usually optimise constrains in iterations, starting with a search distance that's twice my target error and reducing it after each pass.

Let’s say Cyclone apply correction to the C2C registration when it has trigonometric points as a target or not?

Yes, Cyclone will use both constrains to calculate a solution. Set a lower weight on the constrain you want to "give" in the adjustment. For example: set a 0.5 wight for the C2C constrain and leave the target at a 1.0.

- Florentin

[Ioannis]

If you do a registration that contains everything (scans + control) then the scans will be corrected.

Exactly this is what I want to do but how?
I will import control as a .txt and then it will create a new scan world with the 50 control points.
Ithinks thats the best solution because you avoid the drifting of the c2c and have a fixed registration of the beginning.
If we done the registration and then set the weight Cyclone ''carries'' the drifting of scan worlds and tries to correct it.