1. Berit Horvei, Project Manager, SW Hydrography, Subsea Division
Seabed image processing and datacleaning of the EM 3002 Common Data Set
Berit Horvei, Project Manager, SW Hydrography, Subsea Division
WORLD CLASS – through people, technology and dedication

2. Outline Data collection Tide / realtime heave Sound speed variation
Seabed Image processing
Datacleaning
19-Apr-19

3. Data collection R/V Coastal Surveyor
EM 3002 D mounted to the existing ram system onboard
All other sensors supplied by UNH
Used RTK
3 ½ Day with surveying
19-Apr-19

4. Tide / realtime heave Problems with realtime heave
Measured tide from NOAA homepage.
Height values extracted in Neptune
Established modified tide values
18. sept, RTK stasjon 1, svakt signal, falt tidvis ut.
19-21 sept. Ny RTK stasjon, montert på toppen av et fyr.
19-Apr-19

5. Real time heave in the data
 Modified tide file
1 m corridor
x5 Depth scale factor
Calib, 1 m corridor
Gridnavn:
19-Apr-19

6. Sound speed at transducer
Gridded measured sound speed at transducer head.
Small part(red) with wrong sound speed.
19-Apr-19

7. Seabed image processing
Seabed image datagram, corrected for incidence angle
Backscatter, one value / beam
Target, lobster pots, not visible in seabed image frame
Can be identified in the grid.
19-Apr-19

8. Seabed image processing
Seabed image data gridded with a higher resolution than the depth values.
Overlay on top of the ordinary grid
Hvilke parametre brukte jeg.
19-Apr-19

9. Seabed image processing
Seabed image data
Backscatter values gridded
19-Apr-19

10. Seabed image processing
19-Apr-19

11. Seabed image processing
19-Apr-19

12. Datacleaning Line based: Looks at every depth in the current ping.
Removes time- and overhangs errors.
Grid based:
Uses the Tukey-algorithm to construct a curved surface that fits as good as possible to most of the depths in the cell unit.
Does cell splitting and merging to find best possible cell size first.
Reconsiders all depths from previous lines every time the same geographical area is processed.
Uses statistics to remove spikes based on standard deviation, but can also use grazing angle and calculated error estimates for each depth to flag out depths.
19-Apr-19

13. Datacleaning Raw data gridded
Selected area where the sound speed profile created problems.
19-Apr-19

14. Datacleaning Data cleaned in Neptune.
Removed on beam angle, manual inspection and descision
xyz-data from Neptune is gridded in SIS
19-Apr-19

15. Datacleaning Residue standard deviation rule.
Noise removed, but effect of sound speed still visible.
19-Apr-19

16. Datacleaning Residue std. rule
Point data. Red invalid points. Blue valid points.
19-Apr-19

17. Datacleaning Grazing angle rule
For each depth the angle between the beam and the bottom surface is calculated.
19-Apr-19

18. Datacleaning Grazing angle rule
Point data. Red invalid points. Blue valid points.
19-Apr-19

19. Datacleaning Upper left, raw data
Upper right, xyz data, cleaned in Neptune
Lower left, standard deviation rule
Lower right, grazing angle rule
19-Apr-19

20. Summary Tide / realtime heave Sound speed variation
Seabed Image processing
Datacleaning
19-Apr-19

21. Kongsberg Maritime
19-Apr-19