Shallow Survey 2015 Plymouth UK

Shallow Survey 2015 Plymouth UK

Kongsberg Maritime Underwater Mapping Image: Plymouth Area 1 data gathered with GeoSwath 250kHz in March 2015. 50cm grid, mean binning, unsmoothed, no interpolation.

“Shallow Survey 2015” Shallow Survey is the international conference for experts in high resolution surveys in shallow water (< 200 metres). The Common Data Set is a series of surveys conducted using a variety of systems at the same location close to the conference site. This enables delegates to observe and compare how different equipment and techniques work in a common location. The data is peer reviewed. Shallow Survey 2015 theme: High Resolution Surveys in Shallow Water Several sonar survey system manufacturers participated, including: Kongsberg Maritime, Teledyne RESON, Edgetech, and WASSP.

KONGSBERG PROPRIETARY. See statement of proprietary information

03.12.2015

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A visual and statistical comparison of the Shallow Survey 2015 Common Data Sets. Following on from an informal presentation in Plymouth a decade ago, this 2015 presentation will compare the different data sets. The analysis will use 50cm mean binned grids derived from available xyz files. The visual comparisons will use identical areas of interest and equal sun illumination settings, with brief objective comments on coverage, sources and types of error, and some reference to effect on image and final grid quality. This will be linked to a statistical analysis of the differences between all combinations of pairs of grids. The importance of three dimensional sound velocity variations when considering wide swath coverage will be highlighted, and the very large (order of magnitude) differences between sound speed regimes which are characteristic of Plymouth will be discussed for the different data sets. Conclusions will be drawn for both multibeam and phase measurement systems when used in complex estuarine conditions and recommendations will be made for best survey practice.


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General: Coverage was not equal, and data density is a factor in data quality Total area covered by 1m gridded data in the time available 7

Total Area covered (km2)

6 5 4 3 2 1

GS250 2005

MB1

Edgetech

2040

GS250

WASSP

M3

GS500

7125

T20P

0

Edgetech had largest coverage and was the only system to complete all areas. EM2040 used wide swaths and obtained good coverage. GeoSwath 250kHz and M3 did not complete area 2A. WASSP did not complete area 2B. MB1 was not charted as part of area 1 was unavailable. T20P, 7125 and GeoSwath 500 kHz only covered Area 1. GeoSwath 250kHz data from Shallow Water 2005 is shown as reference. KONGSBERG PROPRIETARY. See statement of proprietary information

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Data density over target lines: Edgetech 6205 Reson Having sufficient data density at 50cm7125 – GS250 binning will have little impact on grid statistics (as long as “hits on target “criteria are met) but can have a visible effect on image detail. This is difficult to quantify.


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Data density over target lines: GeoSwath 250kHz 7125 GS250zoom Care must be taken to compareReson imagery at–similar levels etc. otherwise interpretation can be subjective. Therefore we should try to see if the overall grid statistics can be used to objectively compare system performance.


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Create difference grids (in this case using GS4 software) Reson 7125 – GS250


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Step 2. Comparison of all Shallow Survey 2015 Common Data Set grids at 50cm resolution. Check difference grids Basic Quality Control. Some caveats: Data grids are as supplied: It is assumed the manufacturers have processed the data well… Either 50cm grids are used directly or xyz all data points are mean binned on a 50cm grid. Coverage is unequal. Edgetech used equi-angle and equidistant data. EM2040 data is essentially uncleaned, no grid filters are used. MB1 data for Area 1 has 30% soundings rejected and Eastern section was not available. GeoSwath data is filtered at the swath level for outliers and noise, no decimation or grid filters are used. WASSP data has some significant gaps. Sonar related errors should be separated from other error sources. Difference grids are not absolute!

Typical difference histograms

Difference (m)

S

(Check for normal distributions, these examples appear OK)


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Comparison of all Shallow Survey 2015 Common Data Set difference grids at 50cm resolution. Tabulate results Rank order by standard deviation

Mean (m) SD (m) 7125 T20P 0.02 0.077 GS250 M3 -0.29 0.117 EM2040 GS250 0.11 0.123 GS250 MB1 -0.17 0.124 EM2040 GS500 0.03 0.130 EM2040 M3 -0.16 0.131 GS500 M3 -0.18 0.133 GS500 MB1 -0.08 0.135 7125 GS250 1.12 0.138 GS250 GS500 -0.10 0.140 M3 MB1 0.13 0.140 7125 GS500 1.01 0.141 EM2040 MB1 -0.03 0.145 EM2040 Edgetech -0.04 0.146 Edgetech MB1 -0.03 0.146 T20P GS250 1.12 0.147 WASSP MB1 1.09 0.147 7125 Edgetech 0.97 0.148 KONGSBERG PROPRIETARY. See statement of proprietary information

M3 GS250 T20P 7125 7125 T20P Edgetech EM2040 GS500 T20P T20P M3 GS250 7125 GS500 EM2040 T20P EM2040 03.12.2015

Edgetech WASSP GS500 M3 WASSP Edgetech WASSP WASSP WASSP M3 WASSP WASSP Edgetech MB1 Edgetech 7125 MB1 T20P

Mean (m) SD (m) 0.15 0.148 -1.25 0.151 0.99 0.154 0.86 0.157 -0.12 0.157 0.97 0.158 -1.11 0.159 -1.16 0.160 -1.12 0.160 0.84 0.163 -0.14 0.166 -0.98 0.170 -0.14 0.172 0.96 0.179 -0.05 0.182 -1.00 0.185 0.95 0.186 -0.99 0.196 Page 9

Comparison of all Shallow Survey 2015 Common Data Set difference grids at 50cm resolution. Check results Mean (m) SD (m) 7125 T20P 0.02 0.077 GS250 M3 -0.29 0.117 EM2040 GS250 0.11 0.123 GS250 MB1 -0.17 0.124 EM2040 GS500 0.03 0.130 EM2040 M3 -0.16 0.131 GS500 M3 -0.18 0.133 GS500 MB1 -0.08 0.135 7125 GS250 1.12 0.138 GS250 GS500 -0.10 0.140 M3 MB1 0.13 0.140 7125 GS500 1.01 0.141 EM2040 MB1 -0.03 0.145 EM2040 Edgetech -0.04 0.146 Edgetech MB1 -0.03 0.146 T20P GS250 1.12 0.147 WASSP MB1 1.09 0.147 7125 Edgetech 0.97 0.148 KONGSBERG PROPRIETARY. See statement of proprietary information

M3 GS250 T20P 7125 7125 T20P Edgetech EM2040 GS500 T20P T20P M3 GS250 7125 GS500 EM2040 T20P EM2040 03.12.2015


Mean (m) SD (m) 0.15 0.148 -1.25 0.151 0.99 0.154 0.86 0.157 -0.12 0.157 0.97 0.158 -1.11 0.159 -1.16 0.160 -1.12 0.160 0.84 0.163 -0.14 0.166 -0.98 0.170 -0.14 0.172 0.96 0.179 -0.05 0.182 datum -1.00 0.185 0.95 0.186 -0.99 0.196

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Comparison of all Shallow Survey 2015 Common Data Set grids at 50cm resolution: Vertical offsets (m ± 1cm)

-0.03

MB1

There are two “clusters” of vertical offset differences for the manufacturers overall Area 1 grids. Each cluster is consistent to decimetre level. Reson 7125, T20P and WASSP grids were approximately 1m deeper than EM2040, Edgetech, GeoSwath Plus 500kHz, the independent 250kHz and M3, MB1 and the T20P “target” grids and the Reson 8125 grid from 2005.

The mean of the most populated cluster was taken as the best estimate of zero datum. Reanalysis in Caris eliminated this apparent offset in the 7125 and T20P grids. KONGSBERG PROPRIETARY. See statement of proprietary information

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Comparison of all Shallow Survey 2015 Common Data Set difference grids at 50cm resolution. Check results

7125 GS250 EM2040 GS250 EM2040 EM2040 GS500 GS500 7125 GS250 M3 7125 EM2040 EM2040 Edgetech T20P WASSP 7125

T20P M3 GS250 MB1 GS500 M3 M3 MB1 GS250 GS500 MB1 GS500 MB1 Edgetech MB1 GS250 MB1 Edgetech

Mean 0.02 -0.29 0.11 -0.17 0.03 -0.16 -0.18 -0.08 1.12 -0.10 0.13 1.01 -0.03 -0.04 -0.03 1.12 1.09 0.97


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SD 0.077 0.117 0.123 0.124 0.130 0.131 0.133 0.135 0.138 0.140 0.140 0.141 0.145 0.146 0.146 0.147 0.147 0.148

M3 GS250 T20P 7125 7125 T20P Edgetech EM2040 GS500 T20P T20P M3 GS250 7125 GS500 EM2040 T20P EM2040


Mean 0.15 -1.25 0.99 0.86 -0.12 0.97 -1.11 -1.16 -1.12 0.84 -0.14 -0.98 -0.14 0.96 -0.05 -1.00 0.95 -0.99

SD 0.148 0.151 0.154 0.157 0.157 0.158 0.159 0.160 0.160 0.163 0.166 0.170 0.172 0.179 0.182 0.185 0.186 0.196

(Investigate why these comparisons are unexpectedly poor!)

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A visual and statistical comparison of the Shallow Survey 2015 Common Data Sets: x y origins, Reson 7125 and T20P

0.15-0.2 0.1-0.15

50

0.05-0.1 0-0.05

0.2

Shift North (cm)

0.15

SD of difference (m)

0

0.1 0.05 0 -50

Table of Standard deviation values (m) North (cm) 100 50 0 -50

0.219 0.156 0.124 0.148 -50

0.197 0.122 0.077 0.115 0


0.216 0.154 0.124 0.151 50

0

-50

Shift East (cm)

0.265 0.221 0.203

100 East (cm) 03.12.2015

50

Result: These grids are aligned in x and y Page 13

Comparison of the Shallow Survey 2015 Common Data Sets: Grid origins, Reson 7125 and EM2040

0.15-0.2 0.1-0.15

100

0.05-0.1 0-0.05 0.2

Shift North (cm)

0.15


50

0.1 0.05 0 0 50

Table of Standard deviation values (m) North (cm) 100 50 0

0.153 0.147 0.185 0

0.096 0.087 0.146 50


0.114 0.106 0.158 100 East (cm)

Shift East (cm)

0 100

Result: Shifting the Reson 7125 grid by 50cm E and 50cm N minimises the grid differences but residual small “shift” remains 03.12.2015

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Side by side comparison of 50cm resolution difference grids of Reson 7125 and EM2040. Left: grids are as described previously. Right: one grid is shifted 50 cm East. The “red shift” (negative depth difference) moves from the Eastern slope of the Narrows to the Western slope. This suggests a consistent grid difference in Eastings between 0 and 50cm in one of the data sets. KONGSBERG PROPRIETARY. See statement of proprietary information

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A visual and statistical comparison of the Shallow Survey 2015 Common Data Sets. Reson 7125 and GS250

0.15-0.2 0.1-0.15 100

0.05-0.1 0-0.05 0.2

Shift North (cm)

0.15


50

0.1 0.05 0 0 50

Table of Standard deviation values (m) North (cm) 100 50 0

0.15 0.135 0.147 0.094 0.138 0.146 0 50 KONGSBERG PROPRIETARY. See statement of proprietary information

0.174 0.145 0.163 100 East (cm)

Shift East (cm)

0 100

Result: Again, shifting the Reson 7125 grid by 50cm E and 50cm N minimises the grid differences 03.12.2015

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Differentiate between any global navigation datum shift and localised effects

Side by side comparison of 50cm resolution grids, (left) Reson 7125 and (right) GeoSwath 250kHz. Left: The positional difference between two overlapping 7125 swaths creates interference patterns of 20cm to 40cm artefacts on the slope. As the slope is close to 45°, this suggests a localised SVP bias or navigation step error of order 30cm. This is also not a sonar related error. KONGSBERG PROPRIETARY. See statement of proprietary information

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Comparison of all Shallow Survey 2015 Common Data Set grids at 50cm resolution. Shift 7125 and T20P grids and recalculate

7125 EM2040 7125 EM2040 7125 T20P 7125 7125 T20P T20P GS250 EM2040 7125 EM2040 EM2040 T20P GS250 EM2040

Mean (m) SD (m) T20P 0.02 0.077 7125 -1.00 0.082 GS250 1.12 0.094 T20P -0.98 0.095 GS500 1.02 0.100 GS250 1.11 0.101 M3 0.84 0.111 MB1 0.96 0.111 GS500 1.04 0.113 M3 0.82 0.116 M3 -0.29 0.117 GS250 0.11 0.122 Edgetech 0.98 0.123 M3 -0.17 0.123 GS500 0.03 0.123 MB1 0.50 0.124 MB1 -0.17 0.124 MB1 -0.03 0.130


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T20P GS500 EM2040 GS500 GS250 M3 7125 EM2040 Edgetech WASSP M3 GS250 T20P Edgetech GS500 M3 GS250 GS500

Edgetech M3 Edgetech MB1 GS500 MB1 WASSP WASSP MB1 MB1 Edgetech WASSP WASSP WASSP WASSP WASSP Edgetech Edgetech

Mean (m) SD (m) 0.96 0.131 -0.18 0.133 -0.02 0.134 -0.08 0.135 -0.10 0.140 0.13 0.140 -0.14 0.143 -1.14 0.145 -0.03 0.146 1.09 0.147 0.15 0.148 -1.25 0.151 -0.16 0.153 -1.11 0.159 -1.12 0.160 -0.98 0.170 -0.14 0.172 -0.05 0.182

(Investigate possible reasons for higher SD in widest swath comparisons)

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Edgetech 50cm grid of Area 1, full extent KONGSBERG PROPRIETARY. See statement of proprietary information

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Trim all wide swath grids to allow like for like area comparisons. Inclusion of surf zone is likely to affect standard deviation when comparing pairs of wide swath systems

Edgetech 50cm grid of Area 1, shoal areas trimmed to match extent of T20P KONGSBERG PROPRIETARY. See statement of proprietary information

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Comparison of all Shallow Survey 2015 Common Data Set grids at 50cm resolution. Equalise grid areas and recalculate SD

7125 EM2040 7125 EM2040 7125 GS250 T20P EM2040 7125 7125 EM2040 T20P GS250 T20P 7125 GS250 EM2040 T20P

Mean (m) SD (m) T20P 0.00 0.077 7125 1.00 0.082 GS250 1.12 0.088 T20P -0.98 0.095 GS500 1.04 0.098 GS500 -0.09 0.100 GS250 1.11 0.101 GS250 0.13 0.104 M3 0.83 0.111 MB1 0.96 0.111 GS500 0.04 0.112 GS500 1.04 0.113 M3 -0.30 0.115 M3 0.82 0.116 Edgetech 0.99 0.122 Edgetech -0.14 0.124 M3 -0.17 0.124 MB1 0.95 0.124


GS250 GS500 EM2040 T20P GS500 EM2040 GS500 M3 Edgetech 7125 WASSP M3 GS250 T20P EM2040 GS500 Edgetech M3 03.12.2015

MB1 Edgetech MB1 Edgetech M3 Edgetech MB1 MB1 MB1 WASSP MB1 Edgetech WASSP WASSP WASSP WASSP WASSP WASSP

Mean (m) SD (m) -0.17 0.124 -0.05 0.129 -0.03 0.130 0.96 0.131 -0.21 0.132 -0.01 0.133 -0.08 0.135 0.13 0.140 -0.03 0.146 -0.14 0.147 1.09 0.147 0.16 0.149 -1.27 0.151 -0.16 0.153 -1.14 0.153 -1.18 0.163 -1.13 0.164 -0.97 0.173 Page 21

SD (m) 0.077 0.082 0.088 0.095 0.098 0.100 0.101 0.104 0.111 0.111 0.112 0.113 0.115 0.116 0.122 0.124 0.124 0.124 0.124 0.129 0.130 0.131 0.132 0.133 0.135 0.140 0.146 0.147 0.147 0.149 0.151 0.153 0.153 0.163 0.164 0.173

7125 T20P EM2040 GS250

T20P 7125

EM2040

GS250

GS500

M3

MB1

Edgetech WASSP

7125 7125 EM2040

T20P

GS500 GS250 GS250

GS500 T20P EM2040

7125 GS250

M3 MB1

The standard deviation of the differences between 50cm resolution depth grids can be compared. Each pair of systems is tabulated in rank order. Some consistent patterns are now emerging.

7125 7125 GS500

EM2040 T20P

GS500 M3

GS250 T20P

M3 Edgetech

7125 GS250

Edgetech M3

EM2040

MB1

T20P GS250

MB1

Edgetech

GS500

MB1

EM2040

Edgetech

T20P M3

GS500

Edgetech

EM2040 MB1

MB1

GS500 M3 Edgetech

MB1

WASSP

7125 MB1

WASSP Edgetech WASSP WASSP WASSP WASSP WASSP

M3 GS250 T20P EM2040 GS500 WASSP Edgetech M3

Page 22 03.12.2015 KONGSBERG PROPRIETARY. See statement of proprietary information

Comparison of all Shallow Survey 2015 Common Data Set grids at 50cm resolution. Check results 0.18 0.17

SD of grid difference (m)

0.16 0.15

7125

0.14

EM2040

0.13

T20P

0.12

GS250 GS500

0.11

M3

0.10

MB1

0.09

Edgetech

0.08

WASSP

0.07 0.06 1 2 3 4 5 6 7 8 Comparison of each system against all other systems in rank order

At this stage, the products start to differentiate more clearly, (remember coverage for 2040 etc vs 7125!). But there are yet more factors… KONGSBERG PROPRIETARY. See statement of proprietary information

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Reson 7125 SS2015 July 28th – 30th 2014 KONGSBERG PROPRIETARY. See statement of proprietary information

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GeoSwath 250kHz SS2015 2nd - 6th March 2015. Sediments move! Removing obvious sediment shifts in the later data sets, ie EM2040 and GS250kHz further improves SD in comparisons with earlier data sets, but area selection could be arbitrary so was not used in results here. KONGSBERG PROPRIETARY. See statement of proprietary information

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Performance in outer beams (7125), 50cm target sub-grid on left with outer beam performance affecting sharpness of features (even on narrow beam systems). Full Area 1 grid on right now showing clear feature definition. This is sonar related (This affects SD of smaller sub-grids such as target areas, but has little impact on overall full grids due to high overlap)

A grid by grid comparison of all data sets at 50cm binning, illumination first from NS and then EW, no grid filtering or interpolation (data as supplied) Some 2005 grids shown for reference.

8125 2005 targets area 1 sun Illuminated NS scale lines 100m KONGSBERG PROPRIETARY. See statement of proprietary information

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8125 2005 targets area 1 sun Illuminated NS KONGSBERG PROPRIETARY. See statement of proprietary information

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8125 2005 targets area 1 sun Illuminated EW KONGSBERG PROPRIETARY. See statement of proprietary information

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GeoSwath 250kHz 2005 targets area 1 sun Illuminated NS KONGSBERG PROPRIETARY. See statement of proprietary information

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GeoSwath 250kHz 2005 targets area 1 KONGSBERG PROPRIETARY. See statement of proprietary information

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WASSP SS2015 (target areas manually reduced for tide) 7th – 11th July 2014 KONGSBERG PROPRIETARY. See statement of proprietary information

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WASSP SS2015 (target areas have been manually reduced for tide) KONGSBERG PROPRIETARY. See statement of proprietary information

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Edgetech 6205 SS2015 15th -18th July 2014 KONGSBERG PROPRIETARY. See statement of proprietary information

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Edgetech 6205 SS2015 15th -18th July 2014 KONGSBERG PROPRIETARY. See statement of proprietary information

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7125 2015 targets area 1 July 28th – 30th 2014 KONGSBERG PROPRIETARY. See statement of proprietary information

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7125 2015 targets area 1 KONGSBERG PROPRIETARY. See statement of proprietary information

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T20P 2015 targets area 1 July 21st -25th 2014 KONGSBERG PROPRIETARY. See statement of proprietary information

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T20P 2015 targets area 1 KONGSBERG PROPRIETARY. See statement of proprietary information

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MB1 2015 targets area 1 July 21st -25th 2014 KONGSBERG PROPRIETARY. See statement of proprietary information

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MB1 2015 targets area 1 KONGSBERG PROPRIETARY. See statement of proprietary information

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GeoSwath Plus 500kHz SS2015 6th – 8th August 2014 KONGSBERG PROPRIETARY. See statement of proprietary information

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GS500 2015 targets area 1 KONGSBERG PROPRIETARY. See statement of proprietary information

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EM2040D SS2015 9th – 12th September 2014 KONGSBERG PROPRIETARY. See statement of proprietary information

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EM2040 2015 targets area 1 KONGSBERG PROPRIETARY. See statement of proprietary information

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GeoSwath 250kHz SS2015 2nd - 6th March 2015 KONGSBERG PROPRIETARY. See statement of proprietary information

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GS250 2015 targets area 1 KONGSBERG PROPRIETARY. See statement of proprietary information

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M3 2015 targets area 1 2nd - 6th March 2015 KONGSBERG PROPRIETARY. See statement of proprietary information

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M3 2015 targets area 1 KONGSBERG PROPRIETARY. See statement of proprietary information

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WASSP Area 1: SVPs 9th to 11th July 2014 1500 0

1502

1504

1506

Sound speed (m/s) 1508 1510

1512

1514

1516

1518

5 10 15 20 25 30

Area 1 WASSP 09/07/2014 11:26 Area 1 WASSP 10/07/2014 10:46

35

Area 1 WASSP 11/07/2014 11:34

Area 1 WASSP 11/07/2014 13:27 40

All following SVP charts have equal range (18m/s) in horizontal scale to allow visual comparison

SVP variation around 5 m/s across survey area KONGSBERG PROPRIETARY. See statement of proprietary information

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Edgetech Area 1: SVPs 16th & 18th July 2014 1500 0

1502

1504

1506


1512

1514

1516

1518

5 10

depth (m)

15 20 25 30 35

Area 1 16/07/2014 13:10 Area 1 16/07/2014 07:19 Area 1 18/07/2014 10:25

40

SVP variation around 1.5m/s across survey area KONGSBERG PROPRIETARY. See statement of proprietary information

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Reson 7125 Area 1: SVPs 28th July 2014 1508 0

1510

1512

1514


1520

1522

1524

1526

5

Depth (m)

10

15

20 Reson 7125 28/07/2014 10:47 25

Reson 7125 28/07/2014 12:40 Reson 7125 28/07/2014 14:05

30

35

SVP variation around 1m/s across survey area KONGSBERG PROPRIETARY. See statement of proprietary information

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GeoSwath 500kHz Area 1: SVPs 6th August 2014 1506 0

1508

1510

1512

Speed of sound (m/s) 1514 1516

1518

1520

1522

1524

5 10

Depth (m)

15

SVP4 down cast (day 2, deepest Area1-W, 8:28) SVP5 down cast (day 2, deepest Area1-SW, 12:08)

20 SVP6 down cast (day 2, deepest Area1-E, 13:32)

25 30

SVP7 down cast (day 2, deepest Area1-N central, 14:45)

35

40

SVP variation around 1 m/s across survey area KONGSBERG PROPRIETARY. See statement of proprietary information

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EM2040 Area 1: SVPs 11th-12th September 2014 1500 0

1502

1504

1506


1512

1514

1516

1518

5

Depth (m)

10 EM2040 11/09/2014 09:30 15

EM2040 11/09/2014 12:16 EM2040 12/09/2014 10:08

20

25

30

SVP variation around 0.5 m/s across survey area KONGSBERG PROPRIETARY. See statement of proprietary information

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GS250 and M3 Area 1: SVPs 3rd March 2015 1470 0

1472

1474

1476

Sound Speed (m/s) 1478 1480

1482

1484

1486

1488

5

Depth (m)

10

!

15

20

GS 250/M3 Area 1 03/03/2015 11:06 GS 250/M3 Area 1 03/03/2015 11:25

25

GS 250/M3 Area 1 03/03/2015 13:23 GS 250/M3 Area 1 03/03/2015 15:57

30

GS 250/M3 Area 1 03/03/2015 17:24 GS 250/M3 Area 1 03/03/2015 17:32

35

SVP variation around 14m/s across survey area KONGSBERG PROPRIETARY. See statement of proprietary information

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GeoSwath Area 1: SVP transition point within individual survey lines. Use mini SVS data

Approx SVP 1 position Surveying at low tide has impact on coverage and standard deviation

Sound velocity measured at sonar transducers

Approx SVP 2 position

Switch from SVP 1 to SVP 2 at clear SVS transition point KONGSBERG PROPRIETARY. See statement of proprietary information

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Not enough 4-D SVP information in this local shallow area to correct!

GS250kHz: 20cm SVP induced artefacts, Vanguard Bank area 1 Impact of highly variable SVP across survey area and within single survey lines KONGSBERG PROPRIETARY. See statement of proprietary information

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Lower SVP variation allows reduced local errors with lower spatial SVP sampling

GeoSwath Plus 500kHz, no visible SVP artefacts, Vanguard Bank area 1 KONGSBERG PROPRIETARY. See statement of proprietary information

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Reson T20P, used as template to trim other grids, Vanguard Bank. KONGSBERG PROPRIETARY. See statement of proprietary information

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Area 1: Tide Matters! 6

Tide above ACD (m)

5

4

3

2

7125

1

GS500 00:00:00

22:00:00

20:00:00

18:00:00

16:00:00

14:00:00

12:00:00

10:00:00

08:00:00

06:00:00

04:00:00

02:00:00

00:00:00

0

Time of day (hh:mm:ss)

Tidal variation around 4 to 5m during survey day KONGSBERG PROPRIETARY. See statement of proprietary information

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WASSP, area of sea grass, south of degaussing area. Acquired at high tide KONGSBERG PROPRIETARY. See statement of proprietary information

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M3 Sonar, area of sea grass, south of degaussing area. Acquired at low tide Both of these two multibeam systems have 120 degree coverage! KONGSBERG PROPRIETARY. See statement of proprietary information

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Area 1: Tidal variation with location Devonport is slightly North of Survey area 1. Millbay is on the Northern central edge 6

0.1 0.08 0.06 0.04

4

0.02 3

0 -0.02

2

-0.04

Difference (m)

Tide above ACD (m)

5

-0.06

1

-0.08 01/08/2014 00:00

31/07/2014 12:00

31/07/2014 00:00

30/07/2014 12:00

30/07/2014 00:00

29/07/2014 12:00

29/07/2014 00:00

28/07/2014 12:00

-0.1 28/07/2014 00:00

0

Millbay Devonport Difference

Difference in tidal levels could account for decimetre scale errors For example EM2040 did not use post processed heave, and using Millbay tide affected z values near Narrows KONGSBERG PROPRIETARY. See statement of proprietary information

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Area 2: Wembury Bay. 50 cm grid differences NB: These are not all “like for like” comparison areas System grids

Mean

Mode

SD

2040

GS250

Area 2B

-0.02

0

0.123

GS250

M3

Area 2B

-0.1

-0.12

0.125

2040

M3

Area 2B

-0.11

-0.11

0.141

2040

Edgetech

Area 2A

-0.15

-0.14

0.158

GS250

Edgetech

Area 2B

-0.08

-0.09

0.165

Edgetech

WASSP

Area 2A

-1.01

-1

0.168

Edgetech

M3

Area 2B

-0.02

-0.03

0.181

2040

Edgetech

Area 2B

-0.13

-0.12

0.184

2040

WASSP

Area 2A

-1.12

-1.09

0.246

Area 2B is more shoal than Area 2A, but both have mixed sands and silts with rock outcrops. Much of the area has sand ripples fields of various wavelengths from around 70cm up to 2.5m. These wavelengths changed significantly from July 2014 to March 2015, and there is also evidence of bulk sand movement . These factors will most affect the GeoSwath 250kHz and M3 Sonar system data sets. KONGSBERG PROPRIETARY. See statement of proprietary information

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WASSP Area 2A SS2015 (Attempting to find common areas of data overlap) KONGSBERG PROPRIETARY. See statement of proprietary information

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Edgetech 6205 Area 2A SS2015 KONGSBERG PROPRIETARY. See statement of proprietary information

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EM2040D Area 2A SS2015 KONGSBERG PROPRIETARY. See statement of proprietary information

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Edgetech 6205 Area 2B SS2015 KONGSBERG PROPRIETARY. See statement of proprietary information

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EM2040D Area 2B SS2015 KONGSBERG PROPRIETARY. See statement of proprietary information

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Note sand ripple wavelengths here have changed over Winter season

GeoSwath 250kHz Area 2B SS2015 KONGSBERG PROPRIETARY. See statement of proprietary information

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M3 Sonar Area 2B SS2015 KONGSBERG PROPRIETARY. See statement of proprietary information

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GeoSwath 250kHz Area 2B SS2015. 70 to 80 cm wavelength sand ripples are well defined across track using 20 cm grid binning (single pass 2-D filter applied, no interpolation). This requires good calibration & navigation as well as sonar performance KONGSBERG PROPRIETARY. See statement of proprietary information

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Edgetech 6205 Area 2B SS2015. Identical grid settings. The ripples are present on side scan but not clearly resolved in bathymetry due to the lower swath data density. This is not obvious from a statistical analysis. KONGSBERG PROPRIETARY. See statement of proprietary information

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Conclusions The difference in quality of sonar data can be distilled from comparative surveys, but care must be taken in order to approach an objective and impartial “like for like” comparison. As Sonar and processing system technology has incrementally improved, the difference between the final output of higher quality systems has reduced. Other factors can dominate both the total error budget and the user experience. Statistical analysis can be used to differentiate system performance, but side by side visual comparisons using the Common Data Set reveal far more about overall system performance and probable error sources.


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Shallow Survey Recommendations For shallow surveys check tides and design survey line plan to cover shoal areas in higher tide conditions if possible.

Design survey plan to not progress in direction of weather or current drift, this will avoid persistence of vessel wake affecting adjacent lines. Check SVP variations on site and monitor throughout survey. Run test lines to check optimal swath width for wide swath systems. Record sound velocity at sonar as a minimum to reduce impact of SVP. Use the sound velocity information intelligently! Check coverage with test lines on site (shoal and deep). Check weather and plan. Poor weather adds to TPE through increased background noise, increased attitude related error and physical system movement, (as well as effects on operators!).


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THANK YOU Any questions? kongsberg.com