Total propagated uncertainty is computed for every sounding by combining the error budgets of each contributor: positioning, attitude, heading, timing, lever arms, sound speed, draft, squat, tide or ellipsoid separation and the sonar itself. It splits into a horizontal part (THU) and a vertical part (TVU), each compared with the limits of the survey order. Gridding algorithms use it to weight soundings, so a sloppy uncertainty model degrades the final surface as well as the report.
TPU's blowing past the limit on the outer beams, so cap the swath at 55 degrees for this area.
An uncertainty model is only as good as the sensor figures typed into it; copying brochure values produces beautiful numbers and a misleading report.
Also heard as
- total propagated uncertainty
- uncertainty budget
Related terms
TVU
Total vertical uncertainty: the depth part of a sounding's uncertainty, judged against a depth-dependent limit.
THU
Total horizontal uncertainty: how far a sounding's true position could be from where it was recorded, at 95 percent confidence.
CUBE
Combined Uncertainty and Bathymetry Estimator: an algorithm that builds a depth surface by weighting soundings by uncertainty.
S-44
The international minimum standard for hydrographic surveys, setting uncertainty, detection and coverage limits by order.