Environmental Impact on Mine Hunting in the Yellow Sea using the CASS/GRAB Model

Environmental Impact on Mine Environmental Impact on Mine Hunting in the Yellow Sea Hunting in the Yellow Sea

using the CASS/GRAB Modelusing the CASS/GRAB Model

Lt Carlos J. Cintron

Purpose of this study is to determine the Purpose of this study is to determine the necessity of a near real time ocean necessity of a near real time ocean modeling capability such as MODAS for modeling capability such as MODAS for Mine Hunting applications in shallow Mine Hunting applications in shallow water regions.water regions.

PurposePurpose

AN/SQQ-32 Mine Hunting AN/SQQ-32 Mine Hunting Sonar SystemSonar System

The CASS/GRAB Acoustic model input file used in this study was designed to simulate the Acoustic Performance of the AN/SQQ-32.

The AN/SQQ-32 is the key mine hunting component of the U.S. Navy’s Mine Hunting and Countermeasure ships.

Detection Sonar and Detection Sonar and Classification Sonar AssemblyClassification Sonar Assembly

Yellow Sea Bottom Yellow Sea Bottom Sediment ChartSediment Chart

Four Bottom Sediment types were chosen for this Study1.1. MudMud

2.2. SandSand

3.3. GravelGravel

4.4. RockRock

Yellow Sea Bottom TopographyYellow Sea Bottom Topography

Water depth in most of the region is less than 50 m50 m.

Within 50 km of the Korean coastline the average water depth is 20 m20 m.

Seasonal Temperature Profile Seasonal Temperature Profile StructuresStructures

(a) Winter and Fall Temperature Profile Structure.– IsothermalIsothermal

(b) Spring and Summer Temperature Profile Structure.– Multi-layerMulti-layer

Mixed layer Thermocline Deep Layer

Oceanographic Data SetsOceanographic Data Sets

Master Oceanographic Observational Data Set (MOODS)

Generalized Digital Environmental Model (GDEM)

Modular Ocean Data Assimilation System (MODAS)

Master Oceanographic Master Oceanographic Observational Data Set Observational Data Set

(MOODS)(MOODS) Historical world wide observational

oceanographic profile data base dating back to 1920.

Consist of:– Temperature only profiles– Both Temperature and Salinity Profiles– Sound Speed profiles– Surface Temperatures

Biggest limitation is its irregular distribution over time and space.

Generalized Digital Generalized Digital Environmental Model (GDEM)Environmental Model (GDEM)

Gridded Climatological Data derived from MOODS.

Global GDEM has a 30’30’ resolution

U.S. Navy’s Operationally important areas contain resolutions of 20’20’ and 10’10’.

Contains 33, 66, and 1212 month data sets.

Modular Ocean Data Modular Ocean Data Assimilation System (MODAS)Assimilation System (MODAS)

Climatological MODAS (Static)– Gridded Climatological Data derived from MOODS

Near real time Synthetic MODAS (Dynamic)– Inputs Satellite SST and SSH into Climatology via model

algorithms to produce synthetic Temperature and Salinity fields which are in turn used to produce 3-Dimensional Sound Speed Fields.

MIODAS becomes degraded in shallow water regions because SSH is not entered into the model.

Altimetry is not entered into the MODAS model in waters less the 150 m due to satellite orbit errors and other model corrections which amplify the error levels near land.

Comprehensive Acoustic Comprehensive Acoustic Simulation System/Guassian Simulation System/Guassian Ray Bundle (CASS/GRAB)Ray Bundle (CASS/GRAB)

CASS/GRAB is an active and passive range dependent propagation, reverberation, and signal excess acoustic model that has been accepted as a Navy Standard for the frequency bands of 600 Hz600 Hz to 100 kHz100 kHz.

CASS/GRAB Model CASS/GRAB Model DescriptionDescription

The CASS model is the range dependent improvement of the Generic Sonar Model (GSM). CASS performs signal excess calculations.

The Grab model is a subset of the CASS model and its main function is to compute eigenrays and propagation loss as inputs in the CASS signal excess calculations.

CASSComprehensive Acoustic

System Simulation

Propagation Model 1: FAME

Propagation Model 3: COLOSSUSPropagation Model 4: AMOS equations

Backscatter ModelsReverberationNoise Models

Signal to NoiseSignal Excess

Graphic DisplaysSystem Parameters (Beamforming)

Propagation Model 2: GRAB Gaussian Ray Bundle OAML GRAB v1.0

Environmental Interpolations Environmental Model Interpolations Surface and Bottom Forward Loss Volume Attenuation Sound Speed Algorithms Call GRAB

Comprehensive Acoustic Comprehensive Acoustic Simulation System/Guassian Simulation System/Guassian Ray Bundle (CASS/GRAB)Ray Bundle (CASS/GRAB)

In the GRAB model, the travel time, source angle, target angle, and phase of the ray bundles are equal to those values for the classic ray path.

The main difference between the GRAB model and a classic ray path is that the amplitude of the Gaussian ray bundles is global, affecting all depths to some degree whereas classic ray path amplitudes are local. GRAB calculates amplitude globally by distributing the amplitudes according to the Gaussian equation

,

,

exp . ( ) /0

22

205

p rz z

r

Generic Sound Speed ProfileGeneric Sound Speed Profile

Mixed layer– Surface duct may

be generated with a negative shift in SST

Main Thermocline

Deep Sound Channel Axis

Deep Isothermal Layer

Monthly and Annual Mean Sound Speed Monthly and Annual Mean Sound Speed

comparison for Sand bottom for all 12 monthscomparison for Sand bottom for all 12 months

Sound Speed profiles transition from Isotherm in the winter to Multi-layer in the Summer

1480 1485 1490 1495

-40

-20

0

Jan/

Dep

th (

m)

Sound Speed versus Depth (Sand Bottom)

Monthly Annual Mean

1470 1475 1480 1485 1490 1495

-40

-20

0

Feb


1470 1475 1480 1485 1490 1495

-40

-20

0

Mar


1470 1475 1480 1485 1490 1495

-40

-20

0

Apr

/ D

epth

(m

)

1480 1485 1490 1495

-40

-20

0

May

1485 1490 1495 1500 1505 1510

-40

-20

0

Jun

1490 1500 1510 1520

-40

-20

0

Jul/

Dep

th (

m)

1490 1500 1510 1520 1530

-40

-20

0

Aug

1490 1500 1510 1520

-40

-20

0

Sep

1490 1495 1500 1505 1510 1515

-40

-20

0

SPEED (m/s)

Oct

/ D

epth

(m

)

1490 1495 1500

-40

-20

0

SPEED (m/s)

Nov

1488 1490 1492 1494 1496 1498

-40

-20

0

SPEED (m/s)

Dec

AN/SQQ-32 ConceptAN/SQQ-32 Concept Variable depth high

frequency sonar system – Sonar can be place at

various positions in the water column to optimize the detection of either a moored or bottom mines.

In complimenting the AN/SQQ-32 mine hunting sonar system concept in this Study– Two source depths were

chosen. 25 ft25 ft (Above the Mixed

Layer if present) 125 ft125 ft (Within or below

the Mixed Layer if present)

GDEM Seasonal Variability for Signal ExcessGDEM Seasonal Variability for Signal Excess

GDEM /January/ Sand/ SD = 25 ft GDEM /June/ Sand/ SD = 25 ft

GDEM Seasonal Variability for Signal ExcessGDEM Seasonal Variability for Signal Excess

GDEM /January/ Sand/ SD = 125 ft GDEM /June/ Sand/ SD = 125 ft

Acoustic Transmission Under Severe Acoustic Transmission Under Severe

Weather EventsWeather Events

Track of Tropical Depression Kai-Tak over the Yellow Sea for 10-11 July 2000

Satellite Images of Tropical Depression Kai-TakSatellite Images of Tropical Depression Kai-Tak

July 8, 2000 Tropical Cyclone over the East China Sea

July 9, 2000 Tropical Cyclone over the Northern East China Sea

July 10, 2000 Tropical Depression over the Yellow Sea

July 11, 2000 Tropical Depression over the Northern Yellow Sea

Sound Speed and Maximum Detection Range Sound Speed and Maximum Detection Range Differences for a Mud Bottom region and a Differences for a Mud Bottom region and a

Source Depth of 25 ft Source Depth of 25 ft

Sound Speed and Maximum Detection Range Sound Speed and Maximum Detection Range Differences for a Mud Bottom region and a Differences for a Mud Bottom region and a

Source Depth of 125 ftSource Depth of 125 ft

Sound Speed and Maximum Detection Range Sound Speed and Maximum Detection Range Differences for a Sand Bottom region and a Differences for a Sand Bottom region and a


Significant Acoustic Differences in Significant Acoustic Differences in detection ranges as Defined by the Mine detection ranges as Defined by the Mine

Warfare CommunityWarfare Community

A Significant Acoustic Difference in detection range as Defined by the Mine Warfare Community:

Position of Detection ranges of Mine relative to Source

A significant Acoustic Difference exists if:

If Both Detection Ranges are less than 600 yards

Detection Ranges > 100 Yards

If either of THE DETECTION Ranges are greater than or equal to 600 yards

Detection Ranges > 200 Yards

A Significant Acoustic Differences in detection ranges as Defined by the Mine Warfare Community:

Position of Detection ranges of Mine relative to Source

A significant Acoustic Difference exists if:

If Both Detection Ranges are less than 600 yards

Detection Ranges > 100 Detection Ranges > 100 YdsYds

If either of The Detection Ranges are greater than or equal to 600 yards

Detection Ranges > 200 Detection Ranges > 200 YdsYds

Target Depth

Source Depth = 25 ft

Mud Sand

July 10 – July 7 July 15 – July 10 July 10 – July 7 July 15 – July 10

26 ft Lat 36.5N Lon 124.0E490 ydsFigure 62 and 63

Lat 36.5N Lon 124.0E490 ydsFigure 62 and 63

None None

Bottom None None None None

Target Depth


Mud Sand


26 ft

Lat 36.5N Lon 124.0E

490 yds490 yds


490 yds490 ydsNone None

BottomNone None None None

Maximum Significant Acoustic Difference in Maximum Significant Acoustic Difference in detection ranges for MODAS before and detection ranges for MODAS before and

after the Tropical Depressionafter the Tropical Depression (SD =25ft) (SD =25ft)

Maximum Significant Acoustic Difference Maximum Significant Acoustic Difference in detection ranges for MODAS before and in detection ranges for MODAS before and

after the Tropical Depressionafter the Tropical Depression (SD=125ft)(SD=125ft) Target Depth


Mud Sand


26 ft None None None None

Bottom Lat 36.5N Lon 124.0E790 ydsFigure 64 and 65

Lat 36.5N Lon 124.0E810 ydsFigure 66 and 67

None None

Target Depth


Mud Sand


26 ft None None None None

BottomLat 36.5N Lon 124.0E

790 yds790 yds



TemperatureTemperature and Sound and Sound Speed ComparisonsSpeed Comparisons

10 12 14 16 18 20 22 24

-300

-250

-200

-150

-100

-50

0Temperature versus Depth (Lat 36.5 N 124.0 E/ Mud Bottom)

Temperature (Degrees C)

Dep

th (

ft)

July 10, 2000July 7, 2000 July 15, 2000

1490 1495 1500 1505 1510 1515 1520 1525 1530

-300

-250

-200

-150

-100

-50

0

Dep

th (

ft)

Sound Speed (m/s)

Sound Speed versus Depth (Lat 36.5 N 124.0 E/ Mud Bottom)

July 10, 2000July 7, 2000 July 15, 2000

•Slight Decrease in SST of 0.4 0.4 o o CC was

observed between July 7 and 10

-Possibly due to no SST input into the MODAS model from MCSSTS due to heavy cloud cover during the Tropical Depression.

•A decrease in SST of 1.9 1.9 o o CC was observed between July 10 and 15.

-SST from MCSSTS may have been available for input for July 15, but effects of the Tropical depression on SST may have weaken by then.

• The absence of SSH from Satellite Altimeters may have not allowed MODAS to capture the storms effect to the mixed layer

Ray Traces of Profiles with Significant Acoustic Ray Traces of Profiles with Significant Acoustic DifferencesDifferences

July 10, 2000/ Mud/ DR = 770 ydsDR = 770 yds

Moored MineMoored Mine


July 7, 2000/ Mud / DR = 490ydsDR = 490yds

July 15, 2000/ Mud /DR =490ydsDR =490yds

Signal Excess Contours of Profiles with Signal Excess Contours of Profiles with Significant Acoustic DifferencesSignificant Acoustic Differences

Moored MineMoored Mine



July 7, 2000/ Mud /DR = 490ydsDR = 490yds

July 15, 2000/Mud/DR = 490DR = 490yds

Ray Traces of Profiles with Significant Ray Traces of Profiles with Significant Acoustic DifferencesAcoustic Differences

Bottom MineBottom Mine



July 7, 2000/Mud/DR = -775 ydsDR = -775 yds

July 15, 2000/Mud/DR = -810 ydsDR = -810 yds

Signal Excess Contours of Profiles with Signal Excess Contours of Profiles with Significant Acoustic DifferencesSignificant Acoustic Differences

Bottom MineBottom Mine



July 7, 2000/Mud/DR = -775DR = -775 ydsyds

July 15, 2000/Mud/DR = -810DR = -810 ydsyds

Maximum Significant Acoustic Differences in Maximum Significant Acoustic Differences in detection ranges for MODAS versus MOODSdetection ranges for MODAS versus MOODS

Target Depth = 26 ft


Month Mud Sand

1999 2000 1999 2000

February Lt 35.0N Ln 123.5E760 yds

Lt 35.0N Ln 123.5E 760 yds

Lt 35.9N Ln 125.8E840 yds

Lt 35.9N Ln 125.8E840 yds

May Lt 35.0N Ln 123.0E795 yds

Lt 35.0N Ln 123.0E780 yds

Lt 35.9N Ln 126.0E795 yds

Lt 35.9N Ln 126.0E810 yds

August Lt 35.9N Ln 124.4E545 yds

Lt 35.9N Ln 124.4E535 yds

Lt 35.9N Ln 124.8E820 yds

Lt 35.9N Ln 124.8E815 yds

November Lt 36.5N Ln 123.0E840 yds

Lt 36.5N Ln 123.0E840 yds

Lt 35.9N Ln 125.8E765 yds

Lt 35.9N Ln 125.8E765 yds

Target Depth 26 ft


Month Mud Sand

1999 2000 1999 2000

February Lt 35.0N Ln 123.5E

760 yds760 yds

Lt 35.0N Ln 123.5E

760 yds760 yds

Lt 35.9N Ln 125.8E

840 yds840 yds

Lt 35.9N Ln 125.8E

840 yds840 yds

May Lt 35.0N Ln 123.0E

795 yds795 yds

Lt 35.0N Ln 123.0E

780 yds780 yds

Lt 35.9N Ln 126.0E

795 yds795 yds

Lt 35.9N Ln 126.0E

810 yds810 yds

August Lt 35.9N Ln 124.4E

545 yds545 yds

Lt 35.9N Ln 124.4E

535 yds535 yds

Lt 35.9N Ln 124.8E

820 yds820 yds

Lt 35.9N Ln 124.8E

815 yds815 ydsNovember Lt 36.5N Ln 123.0E

840 yds840 yds

Lt 36.5N Ln 123.0E

840 yds840 yds

Lt 35.9N Ln 125.8E

765 yds765 yds

Lt 35.9N Ln 125.8E

765 yds765 yds




Month Mud Sand

1999 2000 1999 2000


Lt 35.0N Ln 123.5E 760 yds

Lt 35.9N Ln 125.8E840 yds

Lt 35.9N Ln 125.8E840 yds


Lt 35.0N Ln 123.0E780 yds

Lt 35.9N Ln 126.0E795 yds

Lt 35.9N Ln 126.0E810 yds


Lt 35.9N Ln 124.4E535 yds

Lt 35.9N Ln 124.8E820 yds

Lt 35.9N Ln 124.8E815 yds


Lt 36.5N Ln 123.0E840 yds

Lt 35.9N Ln 125.8E765 yds

Lt 35.9N Ln 125.8E765 yds

Target Depth = Bottom


Month Mud Sand

1999 2000 1999 2000


900 yds900 yds

Lt 35.0N Ln 123.5E

890 yds890 yds

None None

May None None None None

August None None None None

November None None NoneNone




Month Mud Sand

1999 2000 1999 2000


Lt 35.0N Ln 123.5E 760 yds

Lt 35.9N Ln 125.8E840 yds

Lt 35.9N Ln 125.8E840 yds


Lt 35.0N Ln 123.0E780 yds

Lt 35.9N Ln 126.0E795 yds

Lt 35.9N Ln 126.0E810 yds


Lt 35.9N Ln 124.4E535 yds

Lt 35.9N Ln 124.8E820 yds

Lt 35.9N Ln 124.8E815 yds


Lt 36.5N Ln 123.0E840 yds

Lt 35.9N Ln 125.8E765 yds

Lt 35.9N Ln 125.8E765 yds

Target Depth

26 ft

Source Depth = 50/ 75/ 125 ft

Month Mud Sand

1999 2000 1999 2000


495 yds495 ydsLt 35.0N Ln 123.5E



620 yds620 ydsLt 36.3N Ln 125.0E

620 yds620 ydsNA NA

August None None Lt35.9N Ln124.6E

545 yds545 ydsLt35.9N Ln124.6E

545 yds545 yds

November Lt 35.0N Ln 123.0E

445 yds445 ydsLt 35.0N Ln 123.0E

445 yds445 ydsLt36.0N Ln124.8E

495 yds495 ydsLt 36.0NLn124.8E

495 yds495 yds



Month Mud Sand

1999 2000 1999 2000


Lt 35.0N Ln 123.5E 760 yds

Lt 35.9N Ln 125.8E840 yds

Lt 35.9N Ln 125.8E840 yds


Lt 35.0N Ln 123.0E780 yds

Lt 35.9N Ln 126.0E795 yds

Lt 35.9N Ln 126.0E810 yds


Lt 35.9N Ln 124.4E535 yds

Lt 35.9N Ln 124.8E820 yds

Lt 35.9N Ln 124.8E815 yds


Lt 36.5N Ln 123.0E840 yds

Lt 35.9N Ln 125.8E765 yds

Lt 35.9N Ln 125.8E765 yds

Target Depth

Bottom

Source Depth = 50/ 75/ 125 ft

Month Mud Sand

1999 2000 1999 2000


1000 yds1000 ydsLt 36.4N Ln 124.4E



225 yds225 ydsLt 36.3N Ln 125.0E

315 yds315 ydsNA NA

August None None Lt35.9NLn 125.8E

265 yds265 ydsLt 35.9N Ln 125.8E

225 yds225 yds

November None None Lt35.9NLn 124.6E

205 yds205 ydsLt 35.9N Ln 124.6E

205 yds205 yds


Oceanographic Difference between Oceanographic Difference between

MODAS and MOODSMODAS and MOODS Target Depth = 26 ft


Month Mud Sand

1999 2000 1999 2000


Lt 35.0N Ln 123.5E 760 yds

Lt 35.9N Ln 125.8E840 yds

Lt 35.9N Ln 125.8E840 yds


Lt 35.0N Ln 123.0E780 yds

Lt 35.9N Ln 126.0E795 yds

Lt 35.9N Ln 126.0E810 yds


Lt 35.9N Ln 124.4E535 yds

Lt 35.9N Ln 124.8E820 yds

Lt 35.9N Ln 124.8E815 yds

November

Lt 36.5N Ln 123.0E840 yds

Lt 36.5N Ln 123.0E840 yds

Lt 35.9N Ln 125.8E765 yds

Lt 35.9N Ln 125.8E765 yds

MODAS versus MOODS

February for Mud Bottom Type

1. Oceanographic Difference between MODAS and MOODS

Differences are due to a deficiency in the MODAS climatology, which gives the MODAS profiles a near bottom positive gradient. (See Text)

2. How did this affect the Acoustic Model This near bottom positive gradient produced up bending near the bottom. When the Source was at hull depth both moored and bottom mines detection ranges were over predicted. When the Source was at 125 ft moored mines detection ranges were over predicted and bottom mines detection ranges were under predicted.

3. Prevalence of Problems if any in the Yellow Sea or North East China Sea

This problem was present in approximately 15 % of the MODAS profiles in the Yellow Sea.

Near Bottom Positive Gradient ErrorNear Bottom Positive Gradient ErrorMud bottom/ February/ 35.0 N 123.5 E/ Source Depth = 125 ft

MODAS MOODS

Mud bottom/ February/ 35.0 N 123.5 E/ Source Depth = 125 ft MODAS MOODS

Near Bottom Positive Gradient Near Bottom Positive Gradient ErrorError



Month Mud Sand

1999 2000 1999 2000


Lt 35.0N Ln 123.5E 760 yds

Lt 35.9N Ln 125.8E840 yds

Lt 35.9N Ln 125.8E840 yds


Lt 35.0N Ln 123.0E780 yds

Lt 35.9N Ln 126.0E795 yds

Lt 35.9N Ln 126.0E810 yds


Lt 35.9N Ln 124.4E535 yds

Lt 35.9N Ln 124.8E820 yds

Lt 35.9N Ln 124.8E815 yds


Lt 36.5N Ln 123.0E840 yds

Lt 35.9N Ln 125.8E765 yds

Lt 35.9N Ln 125.8E765 yds

Oceanographic Difference between MODAS and Oceanographic Difference between MODAS and

MOODSMOODS MODAS versus MOODS

November/ Mud Bottom

1. Oceanographic Difference between MODAS and MOODS

Differences were due to the presence of a surface duct when the source depth was at 25 ft. When there was a surface duct in both profiles, it was much stronger in the MOODS profile for most cases. In most cases, MODAS produced surface ducts that were weaker than would be expected. MODAS weakens the gradients in the thermocline.

2. How did this affect the Acoustic Model The surface ducts produce greater detection ranges for a moored mine. The weaker surface ducts produced by MODAS sometimes under predicted the detection range of a moored mine. No significant acoustic differences were observed for a bottom mine due to the presence or absence of a surface duct. When the source depth was within the thermocline the weaker thermocline gradients produced by MODAS caused less down bending of sound propagation. This produced weaker caustics due to less focusing of sound propagation, which in turn caused an under prediction of moored mines. (See Text)

3. Prevalence of Problems if any in the Yellow Sea or North East China Sea

The weaker surface ducts found in the MODAS profiles cannot be determined to be a problem without performing a study of the MODAS climatology. Weaker MODAS thermocline gradients were observed in approximately over 75 % of the MODAS profiles used in this study.

Weakening of Surface DuctWeakening of Surface DuctMud bottom/ November/ 36.5 N 123.0 E/ Source Depth = 25 ft

MODAS MOODS

Weakening of ThermoclineWeakening of ThermoclineMud bottom/ November/ 35.0 N 123.0 E/ Source Depth = 125 ft

MODAS MOODS

Maximum Acoustic Difference in detection ranges for MODAS Maximum Acoustic Difference in detection ranges for MODAS

Versus MODAS plus Gaussian error in Sound speedVersus MODAS plus Gaussian error in Sound speed



Month Mud Sand

1999 2000 1999 2000


Lt 35.0N Ln 123.5E 760 yds

Lt 35.9N Ln 125.8E840 yds

Lt 35.9N Ln 125.8E840 yds


Lt 35.0N Ln 123.0E780 yds

Lt 35.9N Ln 126.0E795 yds

Lt 35.9N Ln 126.0E810 yds


Lt 35.9N Ln 124.4E535 yds

Lt 35.9N Ln 124.8E820 yds

Lt 35.9N Ln 124.8E815 yds


Lt 36.5N Ln 123.0E840 yds



Month Mud Sand

1999 2000 1999 2000


Lt 35.0N Ln 123.5E 760 yds

Lt 35.9N Ln 125.8E840 yds

Lt 35.9N Ln 125.8E840 yds


Lt 35.0N Ln 123.0E780 yds

Lt 35.9N Ln 126.0E795 yds

Lt 35.9N Ln 126.0E810 yds


Lt 35.9N Ln 124.4E535 yds

Lt 35.9N Ln 124.8E820 yds

Lt 35.9N Ln 124.8E815 yds


Lt 36.5N Ln 123.0E840 yds

Target Depth


Mud Sand

Error (m/s) Error (m/s)

1 5 10 1 5 10

26 ft Lt35.4N Ln 124.4E

735 ydsLt 35.4N Ln 124.4E

735 ydsLt 35.4N Ln 124.4E

735 ydsLt 36.3N Ln 125.0E

845 ydsLt 36.3N Ln 125.0E

845 ydsLt 36.3N Ln 125.0E

845 yds

Bottom None Lt 35.4N Ln 124.4E

1000 ydsLt 35.0N Ln 123.5E

990 ydsNone None Lt 35.9N Ln 124.6E

665 yds

Target Depth


Mud Sand


1 5 10 1 5 10

26 ftLt 35. 0N Ln 123.5E

390 ydsLt 36.4N Ln 124.4E

885 ydsLt 35.9N Ln 124.4E

885 ydsNone Lt 35.9N Ln 125.9E

390 ydsLt 35.9N Ln 124.6E

565 yds

Bottom Lt 36.4N Ln 124.4E

1000 ydsLt 35.1N Ln 124.3E

875 ydsLt 35.4N Ln 124.4E

1000 ydsLt 36.4N Ln 124.6E

115 ydsLt 35.9N Ln 125.9E

320 ydsLt 36.4N Ln 124.6E

210 yds

February



Month Mud Sand

1999 2000 1999 2000


Lt 35.0N Ln 123.5E 760 yds

Lt 35.9N Ln 125.8E840 yds

Lt 35.9N Ln 125.8E840 yds


Lt 35.0N Ln 123.0E780 yds

Lt 35.9N Ln 126.0E795 yds

Lt 35.9N Ln 126.0E810 yds


Lt 35.9N Ln 124.4E535 yds

Lt 35.9N Ln 124.8E820 yds

Lt 35.9N Ln 124.8E815 yds


Maximum Acoustic Difference in detection ranges for MODAS Maximum Acoustic Difference in detection ranges for MODAS

Versus MODAS plus Gaussian error in Sound speedVersus MODAS plus Gaussian error in Sound speed



Month Mud Sand

1999 2000 1999 2000


Lt 35.0N Ln 123.5E 760 yds

Lt 35.9N Ln 125.8E840 yds

Lt 35.9N Ln 125.8E840 yds


Lt 35.0N Ln 123.0E780 yds

Lt 35.9N Ln 126.0E795 yds

Lt 35.9N Ln 126.0E810 yds


Lt 35.9N Ln 124.4E535 yds

Lt 35.9N Ln 124.8E820 yds

Lt 35.9N Ln 124.8E815 yds


AugustTarget Depth


Mud Sand


1 5 10 1 5 10

26 ftLt 35.4N Ln 124.4E

550 yds550 ydsLt 35.4N Ln 124.4E

560 yds560 ydsLt 35.4N Ln 124.4E

600 yds600 ydsLt 36.4N Ln 125.9E

810 yds810 ydsLt 36.4N Ln 125.9E

785 yds785 ydsNone

Bottom None None None None Lt 35.9N Ln 124.6E

590 yds590 ydsNone

Target Depth


Mud Sand


1 5 10 1 5 10

26 ft None None None Lt 36.4N Ln 124.4E

530 yds530 ydsLt 36.4N Ln 124.6E

440 yds440 ydsLt 36.4N Ln 124.4E

380 yds380 yds

Bottom None Lt 36.4N Ln 124.4E

595 yds595 ydsNone Lt 36.4N Ln 124.6E

340 yds340 ydsLt 36.4N Ln 124.6E

375 yds375 ydsLt 36.4N Ln 124.6E

755 yds755 yds

Histograms of the Acoustic Difference Distribution throughout the Histograms of the Acoustic Difference Distribution throughout the

Water Column for Source Depth = 125 ft, Mud bottomWater Column for Source Depth = 125 ft, Mud bottom February 15, 2000 August 15, 2000

Effect of Sound Speed Error at Source DepthEffect of Sound Speed Error at Source Depth

No Error +1 m/s Error -1 m/s Error

ConclusionConclusion Capability of CASS/GRAB model … Strong seasonal variability in acoustic

transmission (detection range, signal excess) …. Effect of the tropical cyclone on acoustic

transmission … Error propagation from sound speed profile to

signal excess Capability of MODAS Weakness of MODAS Future Work

Environmental Impact on Mine Hunting in the Yellow Sea using the CASS/GRAB Model

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Transcript of Environmental Impact on Mine Hunting in the Yellow Sea using the CASS/GRAB Model