1cm over 1 square km is 25 tonnes. Airport runway? I don't know the application, I'm guessing for argument's sake.Sub cm accuracy for earthworks....
Hmm, you were previously recommending RTK, not targets, but ok, let's consider targets...If i were to do a job with a gls or sx12 hat large i just wouldn't quote. What a pita this would be to scan.
Loads of people moan and have comments about a Riegl system but have never used one. With the use of targets you can get sub cm accuracy overall. It's just procedures followed.
I haven't seen anyone moaning about the Reigl, maybe I missed those comments. Would I want to use a Riegl system for the entire job? How would it handle vibrations from an operating plant when it's tripod mounted on gridmesh walkways? The NavVis VLX is more accurate in an environment subject to vibrations. Each tool has its place. The Reigl can no more replace the SX12, than it can replace the NavVis VLX, but it can be used with both those tools, sure.
You're doing pretty well if you're getting sub cm accuracy overall, did you perform least squares analysis on control for target positioning?
We had a lot of base station data, 18 weeks of static observations processed by AUSPOS, position accuracy was 1 mm after using GNSS vectors and covariance matrices from AUSPOS in least squares, with the rest of the control network sub 4mm, most around 3mm. Other GNSS locations we processed 2 weeks of static data for 4mm position accuracy, and 4 weeks for 3mm, we checked GNSS for level and position daily, they ran off solar. I'm quoting absolute position accuracy in GDA2020 @ 95% confidence, referring back to fiducial coordinates, for our control, then I need to add in accuracy for the scans, which is additional to control, which means I'm approaching the accuracy you claim to achieve using the Reigl? Most people do at most 24 hours static GNSS observations, and that's not going to be sub cm.
The Reigl isn't designed to position over a point, it's resected into position when using targets, when you position an SX12 or GLS over control, with precise centring prisms for targets at 100m, and the entire network is least squares adjusted, it gives you confidence. Scanner targets have 2mm std deviation target centring. Prisms can be placed at distance outside the scan. The Reigl is faster and more accurate than a Leica RTC360, but it can't match the accuracy of a least squares adjusted GLS and SX12 network, nor can the latter match the speed of a Reigl or RTC. If scan targets aren't measured by a total station and adjusted using least squares, then the registration will accumulate errors.
My point is, we have to go to extreme lengths to achieve the sort of accuracy you're quoting, and we're taking care to level and centre over every control point with precision.
If there's not much information in the environment to register to, RTK (30 second occupations) with IMU isn't going to provide high accuracy, but then maybe high accuracy isn't required, but that's what you recommended.
I can't just grab one tool and recommend it for all jobs, I know you like your scanner, and you want to tell everyone how great it is, there's nothing wrong with that, but I suspect you might have some familiarity bias. I think there's more to be understood about the application before making a recommendation in this case.