A workable Schema for Editing MBES Backscatter Data Acquired in Shallow Water

1. A workable Schema for Editing MBES Backscatter Data Acquired in Shallow Water Lloyd Huff, Luciano Fonseca, Tianhang Hou Center for Coastal and Ocean Mapping (CCOM), University of New Hampshire, Durham NH and Robert McConnaughey Alaska Fisheries Science Center, NMFS/NOAA, Seattle WA Shallow Survey 2008

2. EFH RESEARCH INCLUDES STUDIES OF THE WATERS AND SUBSTRATES NECESSARY TO FISH FOR SPAWNING, FEEDING AND GROWTH TO MATURITY Shallow Survey 2008

3. BERING SEA EFH RESEARCH SURVEY PLAN AUGUST 2006 Shallow Survey 2008

4. Multibeam Sonars: Reson 8111, Reson 8160 Length: 70.4 m Beam: 12.8 m Draft: 4.7 m Shallow Survey 2008

5. NOAA SHIP FAIRWEATHER EFH OPERATING MODE Shallow Survey 2008

6. TOWED 455 KHZ KLEIN SYSTEM 5000 SIDESCAN SONAR Shallow Survey 2008

7. MBES-DATA ACQUISITION RESON 8111, 8160 DATA WERE ACQUIRED USING GAINS AND POWER SETTINGS ACCORDING TO AN EFH OPERATIONAL PROTOCOL, AS OPPOSED TO THE FAIRWEATHER’S NORMAL HYDROGRAHIC OPERATIONAL PROTOCOL. RESON DATA WERE ACQUIRED ON THREE SEPARATE TRAVERSES OF THE SURVEY LINES. TWO PASSES WERE SW-TO-NE AND ONE PASS WAS NE-TO-SW. Shallow Survey 2008

8. MBES-DATA PROCESSING THE RESON 8111, 8160 BATHYMETRY DATA WERE PROCESSED/ EDITED VIA CARIS. THE RESON 8111, 8160 BACKSCATTER DATA WERE PROCESSED VIA GEOCODER. FOR EFH STUDIES, THE PRIMARY OUTPUT OF THE BACKSCATTER PROCESSING NEEDS TO BE QUANTITATIVE STATISTICAL DATA, RATHER THAN QUALITATIVE VISUAL IMAGERY. Shallow Survey 2008

9. MBES-DATA PROCESSING PRIOR TO MOUNTING A MAJOR DATA CRUNCHING EFFORT IT WAS DEEMED IMPORTANT TO ESTABLISH THE “BEST” SPATIAL RESOLUTION FOR THE BACKSCATTER STATISTICAL OUTPUTS. THAT LED TO COMPUTATIONS OF SPATIAL POWER SPECTRA OF BACKSCATTER AT A 45 DEG GRAZING ANGLE ALONG THE SURVEY LINES. Shallow Survey 2008

10. PROBLEM: THERE WAS A NOTABLE DIFFERENCE BETWEEN THE THREE SPECTRA REPRESENTING BACKSCATTER OF THE THREE PASSES ALONG THE SURVEY LINES. FOR SURVEY LINES 1-2, THE SPECTRA GROUPED INTO A SET OF TWO AND ONE OUTLIER. CAUSE? AT FIRST, IT WAS THOUGHT THERE MIGHT BE A SIGNIFICANT DIRECTIONAL CHARACTER TO THE BACKSCATTER, WHICH IF TRUE, WOULD INVALIDATE THE CONCEPT OF USING ACOUSTIC BACKSCATTER AS A MAJOR COMPONENT IN ANY EFH MODEL FOR THE EASTERN BERING SEA. Shallow Survey 2008

11. RESON 8111 DATA THE SPECTRA INDICATED THE DISTRIBUTION OF ENERGY BECAME “WHITE” AT SPATIAL FREQUENCIES OF 1-2 CYCLES PER KILOMETER Shallow Survey 2008

12. CAUSE? EXAMINATION OF THE OUTPUTS FROM THE MULTIBEAM SONARS INDICATED THAT THERE WERE A NUMBER OF INSTANCES WHERE THE OUTPUT MAY NOT REPRESENT BACKSCATTER MEASUREMENTS THAT COULD TRULY BE RADIOMETRICALLY CORRECTED. TWO TYPES OF “NOISE” WERE ISOLATED: (1) WHERE THE SONAR OUTPUT FLUCTUATED BETWEEN NORMAL AND “TOO HIGH”; AND (2) WHERE THE SONAR OUTPUT FLUCTUATED BETWEEN NORMAL AND “TOO LOW”. Shallow Survey 2008

13. TYPE 1 “NOISE” PROBLEM, AS SEEN IN RESON 8160 DATA IMPACT OF “SCREAMING” SHAFT BEARING THE SONAR OUTPUT DEFINITELY DID NOT REPRESENT BACKSCATTER SIGNALS. Shallow Survey 2008

14. TYPE 2 “NOISE” PROBLEM, AS SEEN IN RESON 8111 DATA IMPACT OF BUBBLE SWEEP DOWN? UNCERTAINTY IN SOURCE LEVEL MAKES IT IMPOSSIBLE TO PERFORM VALID RADIOMETRIC CORRECTIONS ON THE SONAR OUTPUT: QUANTITATIVE BACKSCATTER STATISTICS ARE UNKNOWABLE. Shallow Survey 2008

15. A SOLUTION: INCORPORATE A NESTED PAIR OF SLIDING WINDOWS IN GEOCODER TO DETECT AND FLAG SHORT PING SEQUENCES WHERE THE REPORTED BACKSCATTER WAS EITHER TOO LOW OR TOO HIGH, RELATIVE TO THE LOCAL NORMAL VALUE OF REPORTED BACKSCATTER. DEVELOP A LIST OF FLAGGED PING INTERVALS WHICH BECOMES PART OF THE GEOCODER PROJECT FILE SUCH THAT FLAGGED PING INTERVALSCAN BE PASSED OVER WHEN PERFORMING THE GEOCODER FUNCTIONS. Shallow Survey 2008

16. RESON 8160 DATA Shallow Survey 2008

17. RESON 8160 DATA Shallow Survey 2008

18. Shallow Survey 2008

19. TABLE OF EXCLUDED PING TIME INTERVALS BASED SOLEY ON BACKSCATTER OBJECT FUNCTION 1155328724.121 1155328724.543 1155328724.333 1155328724.755 1155328765.304 1155328765.726 1155328765.516 1155328765.938 1155328765.726 1155328766.148 1155328765.938 1155328766.360 1155328835.211 1155328835.633 1155328835.421 1155328835.843 1155328856.117 1155328856.541 1155328859.075 1155328859.497 1155328862.031 1155328862.453 1155328864.987 1155328865.411 1155328867.945 1155328868.367 1155328870.903 1155328871.325 1155328873.859 1155328874.283 1155328876.817 1155328877.239 1155328879.773 1155328880.195 1155328882.729 1155328883.151 1155328885.687 1155328886.109 THE TEXT FILE OF EXCLUDED PING TIME INTERVALS CAN BE AUGMENTED TO INCLUDE PSEUDO-PING INTERVALS BASED ON PARAMETERS SUCH AS: VESSEL PITCH, VESSEL HEAVE, SONAR GAIN SETTINGS, ETC, WHICH CAN READILY BE RETRIEVED FROM THE “GSF” REPESENTATION OF THE DATA SET. Shallow Survey 2008

20. RESULT: QUESTIONABLE DATA IS EXCLUDED FROM GEOCODER MOSAIC, GEOCODER STATISTICS, AND GEOCODER SEDIMENT INVERSION ANALYSIS MOSAIC OF ORIGINAL DATA MOASIC OF EDITED DATA Shallow Survey 2008

21. RESON 8111 DATA Shallow Survey 2008

22. EDITED 8111 DATA Shallow Survey 2008

23. EDITED MBES RESON 8111, 8160 DATA Shallow Survey 2008

24. EDITED MBES RESON 8111, 8160 DATA 1 degree Longitude ~ 60 kilometers in the Eastern Bering Sea (~57 N Latitude) Shallow Survey 2008

25. CONCLUSIONS: THIS RESEARCH HAS ESTABLISHED A FLEXIBLE AND EXPANDABLE SCHEMA FOR EDITING BACKSCATTER FROM MULTIBEAM SONARS. EDITING BACKSCATTER IS AN IMPORTANT DATA PROCESSING STEP FOR EFHSTUDIES, BECAUSE CHARACTERIZATION OF ACOUSTICBACKSCATTER FOR USE IN AN ESSENTIAL FISH HABITATMODEL REQUIRES QUANTIFIABLE STATISTICAL DATA.