added value brought by auv’s in the surveillance of exploited marine sand banks
DESCRIPTION
Added value brought by AUV’s in the surveillance of exploited marine sand banks. G.Pichot, A.Norro, J.Ozer MUMM. Sources of error. International Hydrographic Norms. In coastal areas for 20 meters depth - horizontal accuracy : 6 meters - depth accuracy : 0.564 meters. - PowerPoint PPT PresentationTRANSCRIPT
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM
Added value brought by AUV’s in the surveillance of exploited marine sand banks
G.Pichot, A.Norro, J.Ozer
MUMM
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMMPrecision of thedata
Type (on the scaleof a profile)
Tidal reduction ±13 cm systematic
Static draught ±5.0 cm systematic
Var. in stat. draught ±5.0 cm systematic
Speed of sound ±2.5 cm systematic
Subtotal systematic ±25.5 cm
Echosounder ±4.0 cm random
Error in navigation ±8.5 cm random
Heave ±2.5 cm random
Presence of slopes +8.0 cm random
Subtotal random - 15 cm / +23 cm
Total error -40.5 cm/+48.5 cm
Sources of error
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM International Hydrographic Norms
In coastal areas for 20 meters depth
- horizontal accuracy : 6 meters - depth accuracy : 0.564 meters
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM The tidal reduction problem
H = H mes. - H T.
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM
Transects over the Kwintebank
(provided by MUMM) rG19 - rH01
-3000 -2000 -1000 0 1000 2000 3000-3000
-2500
-2000
-1500
-1000
-500
0
-3000 -2000 -1000 0 1000 2000 3000-2600
-2400
-2200
-2000
-1800
-1600
-1400
-1200
meters meters
cent
imet
ers
cent
imet
ers
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM The I3S approach
- Shape of the bank is stable
- Profiles are re-aligned wrt first profile
- A constant offset (vertical) and a constant horizontal shift are determined
- Criteria : minimisation of the distance wrt first profile
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM-150
-100
-50 0 50 1000
5
10
15
20
25
-50 0 50 100 1500
5
10
15
20
Offset in cm
Alignment correction : histogram of the observed vertical offset
Compatible with the systematic part of the error budget
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMMDeviation wrt the mean profile (rG19)
-50 0 50 100
0150
0
500
1000
1500
2000
2500 Error max 100 cm
compatible with the random part of the error budget
-100 -50 0 50 100 (cm)
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM
rG21 error max 250 cm rH01 error max 150 cm
MUMM’s random error budget explains only 100 cm
200 100 0 100 200 -200 -150 -100 -50 0 50 100 150 2000
100
200
300
400
500
600
700
800
900histogram of variations wrt to average profile
-400
-300
-200
-100
0 100 200 3000
200
400
600
800
1000
1200
Deviation wrt the mean profile (rG21 and rH01)
-200 -100 0 100 200 (cm) 150 100 50 0 50 100 150 (cm)
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM Volume consideration
Volume variation
MUMM I3S
RG19 Yes No
RG21 Yes Yes
RH01 Yes Yes
Should a part of the volume variation be extracted from a trend in the alignement ?
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM
Do we need a tidal reduction ?
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM Offset with non tidally reduced data
0
1
2
3
4
56
7
8
9
10
-29
0
-25
0
-21
0
-17
0
-13
0
-90
-50
-10
30
70
11
0
15
0
19
0
23
0
27
0
Offset (cm)
# o
f p
rofi
les
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM Conclusion
With non tidally reduced data
Win one third of the systematic error
Increased offset making the trend identification more difficult
Interest to compare or to combine the two approaches
Nice, 17-18 December 2001
Underwater Robotics for Ocean Modelling and Monitoring
HWU
I3S
IST
TMS
MUMM
Volume decrease
5060708090
100110120130140150
10 40 70 100
130
160
190
220
250
280
310
340
370
400
# of profiles
Ret
riev
ed t
ren
d (
m3/
m)
Need more data
Conclusion(2)