30 July 2004USM 2004 Upper Pearl Survey1 Vertical Uncertainty Total Propagated Error –Error budget using Excel spreadsheets created for NAVOCEANO by Rob Hare –TPE for every sounding using CARIS HIPS v5.4 Cross check analyses using Fledermaus –Multi-beam vs. Multi-beam –Single-beam vs. Single-beam –Multi-beam vs. Single-beam PPK/Heights

30 July 2004USM 2004 Upper Pearl Survey2 Vertical Uncertainty Factors taken into account for error budget calculation –Depth variation: 1-25m –Sea state: 0 –River bottom slope: 2 o –Water temperature: 28 o C –Salinity: 0 –Vessel roll/pitch < 1 o –Maximum swath angle for EM3000: 60 o (113 out of 127 beams)

30 July 2004USM 2004 Upper Pearl Survey3 Vertical Uncertainty Sounding error budget –Static and dynamic draft measurement uncertainties –Offset measurement uncertainties –Refraction errors –Sounding system limitations –Vessel motion measurement uncertainties –Tide and vertical datum uncertainties –And…

30 July 2004USM 2004 Upper Pearl Survey4 Vertical Uncertainty Draft and Offset measurements Hare, R., Error budget analysis for NAVOCEANO hydrographic survey systems, MS, 2001.

30 July 2004USM 2004 Upper Pearl Survey5 Vertical Uncertainty Refraction Post survey analysis.

30 July 2004USM 2004 Upper Pearl Survey6 Vertical Uncertainty Sounder accuracy and vessel motions Manufacturer specifications

30 July 2004USM 2004 Upper Pearl Survey7 Vertical Uncertainty Tide and sounding datum uncertainties (at 95% C.I.) –Tide gauge measurements0.02 –Datum recovery0.04 –Use of old epoch0.02 –Tidal zoning0.03

30 July 2004USM 2004 Upper Pearl Survey8 Vertical Uncertainty At 1 mAt 25 m IHO S-44 Order-1 requirement :0.5 m0.596 m a=0.5m b=0.013 d=1 to 25m Total uncertainty:0.096 m0.221 m + DATUM TRANSFER UNCERTAINTY

30 July 2004USM 2004 Upper Pearl Survey9 Vertical Uncertainty Total Propagated Error –The Fourth Edition of S-44 [IHO, 1998] recommends that: “All soundings should be attributed with a 95% statistical error estimate for both position and depth.” –CARIS HIPS v5.4 uses the same approach as in previously mentioned Hare Error Model and propagates the error values to grid nodes of an uncertainty surface, using the actual vessel motion, depth and slope information instead of using average values. –The same constant values used in spreadsheets were also used in HIPS.

30 July 2004USM 2004 Upper Pearl Survey10 Vertical Uncertainty Total Propagated Error –1m grid resolution used for this survey –The resulting grid then was exported to an ASCII file –HIPS doesn’t have a device model for Knudsen 320 (only some multi-beam systems are supported) so TPE could only be calculated for the multi-beam survey

30 July 2004USM 2004 Upper Pearl Survey11 Vertical Uncertainty TPE

30 July 2004USM 2004 Upper Pearl Survey12 Vertical Uncertainty PPK/GPS Heights –PPK/GPS data was collected both on Bertram and Skiff throughout the survey. Alternative to classical tide measurement for reducing the soundings to chart datum Tie the soundings directly to the ellipsoid for a seamless datum –Noisy due to obstruction of trees, especially for Skiff which ran lines across the river.

30 July 2004USM 2004 Upper Pearl Survey13 Vertical Uncertainty PPK/GPS Heights needed filtering –Epochs that had  height > 0.25m filtered, then gaps interpolated, –Furthermore, epochs that had heights > 1.5*mean(  height ) filtered iteratively until mean(  height ) < 1m

30 July 2004USM 2004 Upper Pearl Survey14 Vertical Uncertainty PPK/GPS Heights Mean : m Median : m St.Dev. : m Mean : m Median : m St.Dev. : 0.11 m 0.5m

30 July 2004USM 2004 Upper Pearl Survey15 Vertical Uncertainty Range: 33 cm Range: 5 cm Range: 2 cm 23 June 2004, Bertram

30 July 2004USM 2004 Upper Pearl Survey16 Vertical Uncertainty Cross check analysis –Due to relatively big size of Bertram it wasn’t possible to run systematic multibeam cross check lines, –Main singlebeam lines served as check lines for multibeam data => ~750 cross check lines, Order- 1 requirement satisfied! –Fledermaus Cross Check Analysis tool used for the analyses, –All soundings used for the reference DTM instead of a decimated shoal/deep biased sounding set

30 July 2004USM 2004 Upper Pearl Survey17 Vertical Uncertainty Multibeam vs. Multibeam # of points compared Mean Median Std. Deviation % Order 1 Error Limit 0.50 Order 1 - # Rejected 477 (99.97% ACCEPTED) Order 1 Survey ACCEPTED

30 July 2004USM 2004 Upper Pearl Survey18 Vertical Uncertainty Singlebeam vs. Singlebeam # of points compared Mean Median Std. Deviation % Order 1 Error Limit 0.51 Order 1 - # Rejected 457 (99.96% ACCEPTED) Order 1 Survey ACCEPTED

30 July 2004USM 2004 Upper Pearl Survey19 Vertical Uncertainty Multibeam vs. Singlebeam # of points compared Mean Median Std. Deviation % Order 1 Error Limit 0.51 Order 1 - # Rejected (96.6% ACCEPTED) Order 1 Survey ACCEPTED BUT…

30 July 2004USM 2004 Upper Pearl Survey20 Vertical Uncertainty Cross check summary (Estimated max. error (95% C.I.): 22 cm) –MB vs. MB : 11 cm –SB vs. SB : 50 cm Initial cross check analysis between MB and SB datasets showed a mean offset of 25cm (SB deeper) due to –Bad channels of EM3000 transducer –Accepted Bertram as it is, no ground truth of soundings Did not perform bar-check on Bertram Did not measure static draft This could be seen only after applying the tides because PPK/GPS heights were noisy.

30 July 2004USM 2004 Upper Pearl Survey21 Vertical Uncertainty On the other hand, Skiff was calibrated daily using bar check. Furthermore soundings from Skiff matched to lead line measurements within 10 cm (95%) As a result, mean difference between the two data sets was applied as static draft to MB data.

30 July 2004USM 2004 Upper Pearl Survey22 Vertical Uncertainty Lessons learned –Make sure that you thoroughly know the equipment/software you use. –Use every possible way to ground truth your soundings; a simple lead line measurement may be as important as a complicated patch test.

Processing: Horizontal Uncertainty Debbie Mabey