U.S Department of the Interior

U.S. Geological Survey

CRUISE REPORT

RV OCEAN ALERT CRUISE A1-98-HW

January 30 through February 23, 1998

Honolulu to Honolulu, Hawai'i

James V. Gardner1 and John Hughes-Clarke2

Open-File Report

98-212

A jointly funded project by the US Corps of Engineers, US Environmental Protection

Agency, and the US Geological Survey

Conducted under a Cooperative Agreement between the US Geological Survey and the

Ocean Mapping Group, University of New Brunswick

This report is preliminary and has not been reviewed for conformity with U.S. Geological

Survey editorial standards. Use of trade, product, or firm names in this report is for

descriptive purposes only and does not imply endorsement by the U.S. Government.
1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025

2Ocean Mapping Group, University of New Brunswick, Fredericton, NB E3B 5B3

1998
1

CRUISE REPORT

RV OCEAN ALERT CRUISE A1-98-HW

MAPPING HAWAII INSULAR SLOPES

James V. Gardner1 and John E. Hughes-Clarke2

1US Geological Survey Menlo Park, CA 94025

2Ocean Mapping Group, University of New Brunswick, Fredericton, NB

Cruise Objectives

The major objective of cruise A1-98 was to map portions of the insular slopes of

Oahu, Kauai, Maui, Molokai, and Hawaii and to survey in detail US Environmental

Protection Agency (USEPA) ocean dumping sites using a Simrad EM300 high-resolution

multibeam mapping system. The cruise was a jointly funded project between the US

Army Corps of Engineers (USCOE), USEPA, and the US Geological Survey (USGS).

The USACOE and EPA are interested in these areas because of a series of ocean dump

sites off Oahu, Kauai, Maui, and Hawaii (Fig. 1) that require high-resolution base maps for

site monitoring purposes. The USGS Coastal and Marine Geology Program has several

on-going projects off Oahu and Maui that lack high-precision base maps for a variety of

ongoing geological studies. The cruise was conducted under a Cooperative Agreement

between the USGS and the Ocean Mapping Group, University of New Brunswick,

Canada.

The Simrad EM300 High-Resolution Multibeam Mapping System

This cruise pioneered the use of the Simrad EM300 high-resolution multibeam

mapping system in the U.S. This system simultaneously collects georeferenced

backscatter (similar to a sidescan image) and bathymetry with precise spatial referencing.

The advantage of the Simrad EM300 over all other competing systems is that each depth

determination is calculated from a phase detection as well as an amplitude detection, and

then the "best" solution is selected, based on a set of statistical, quality-control parameters.

The only operational Simrad EM300 system presently in the U.S. is owned and operated
2

by C&C Technologies, Lafayette, LA., and is hull mounted on the leased Canadian-flag

MV Ocean Alert, a 1,750 ton, 71-m , converted Canadian Coast Guard ship (Fig. 2).

Figure 1. Index map of Hawaiian Islands and the areas surveyed during cruise A1-

98-HW. Contour interval 1000 m.

Figure 2. The RV Ocean Alert
3

The EM300 system is a 30-kHz multibeam sonar system with up to 135 individual 1°

(vertical) x 2° (horizontal) electronically formed beams (see Appendix 1 for details). The

swath width and number of beams used during a survey is dependent on the water depth

and mode of operation (see Table 1). The system can be operated in either equal-angle or

equal-distance mode. The equal-angle mode generates 135 1°x2° receive beams and is

configured so that, as the beam number increases from nadir, the size of the area imaged

by each beam progressively increases. The equal-distance mode varies the individual beam

angles so that the same size area is imaged by each beam, regardless of the angle away

from nadir the beam is pointing. The Hawaiian surveys were operated in equal-angle

mode because our initial sea trial off Honolulu showed this mode produced the best results

in the 200 to 1500-m water depths we intended to survey. The EM300 incorperates roll,

pitch, yaw, and heave compensations utilizing a POS/MV motion sensor that detects

motions to 0.01° (Table 2). Yaw steering electronically separates the receive beam into 6

segments (3 per side) and steers each segment to compensate for ship yaw. This

innovation provides a much more accurate geographic determination of the location of

individual depth/backscatter values on the seafloor. The ship's heading was determined

with a dual DGPS system with accuracies <0.1°. Positions and time stamps were

provided with a kinematic DGPS system that gave reliable fixes one per second with ± 1-

m accuracy.

Table 1 Optimum water depths vs modes for the EM300 system

water depth (m) mode fixed swath width (m)

10 to 50 very shallow 150°

50 to 200 shallow 1500

200 to 700 meduim 1500

700 to 2200 deep 3000

>2200 very deep 3000

Sound velocity profiles (SVP) were calculated several times each day so that raytracing

techniques could be used to determine the effect of acoustic refraction in the water
4

principally caused by variations in water temperature. Accurate ray tracing allows the

precise location of each beam’s projection on the seafloor. A SeaBird CTD was deployed

at least once a day to get a good reference SVP, but this measurement requires the ship to

hove to and a typical cast took about 30 minutes. Sippican T5 expendable

bathythermographs (0 to 1830-m water depth) were routinely collected several times a day

to determine water structure because they could be obtained while underway. Two

additional sound velocity profilers are installed at the transducer arrays to determine the

speed of sound in water directly at the transducer. All the SVP data are fed directly into the

Simrad EM300 processor for instantaneous raytracing of the individual beams.

Table 2. Systems Specifications

Simrad EM300............................see Appendix 1

135 1°x2° beams

6 kw output power

source 240 dB (ref 1μPa @ 1 m)

mode...................................................equal angle

active roll, pitch, heave, and yaw compensation

positioning.................................................DGPS

heading (gyro) ................................... dual DGPS

motion sensing ................... POS/MV model 320

water velocity......................... daily SeaBird CTD

several/day T5 XBTs

Like many of the state-of-the-art high-resolution multibeam mapping systems, the

Simrad EM300 utilizes both amplitude (backscatter) and phase detection (bathymetry), but

unlike any others, the EM300 uses both for each determination of the bottom depth for

each beam, resulting in a measurement accuracy of <0.2% of water depth (RMS). Details

of high-resolution multibeam mapping systems can be found in Hughes-Clarke, et al.

(1996). 

 The Party Chief, Mr. Art Kleiner, oversaw a staff of surveyors and programmers

from C & C Technologies, Inc who operated the EM300 system. The data were processed
5

aboard ship by the senior author (JVG) and several graduate students from the Ocean

Mapping Group, University of New Brunswick (Table 3). 

Table 3. Scientific Staff of cruise A1-98

Name Dates aboard vessel

Capt. George Brawley ................................................................. 1/30-2/23

Mr. James Chance, C&C Technologies ....................................... 1/30 -2/4

Mr Art Kleiner, C&C Technologies............................................ 1/30-2/23

Dr. John Hughes-Clarke, OMG, Univ. of New Brunswick.......... 1/30-2/4

Dr. James V. Gardner, USGS..................................................... 1/30-2/23

Mr. Mike Torresan, USGS............................................................ 1/30-2/4

Mr Tim Patro, C&C Technologies.............................................. 1/30-2/23

Mr. Pablo Mejia, C&C Technologies.......................................... 1/30-2/23

Mr. Guy Guidry, C&C Technologies.......................................... 1/30-2/23

Mr. Ryan Larsen, C&C Technologies......................................... 1/30-2/23

Mr. Edouard Kammerer, OMG, Univ. of New Brunswick........ 1/30-2/23

Mr. Sean Galway, OMG, Univ. of New Brunswick................... 1/30-2/23

Mr. Luciano Fonseca, OMG, Univ. of New Brunswick............... 2/4-2/10

Mr. Hou Tianhang, OMG, Univ. of New Brunswick................. 2/10-2/23

Mr. Kjell Nilsen, Konsberg Simrad .............................................. 1/30-2/6

Mr. Rolf Iversen, Konsberg Simrad.............................................. 1/30-2/4

All post-cruise processing will be performed by JVG. Data processing (Fig. 3) consisted

of (1) editing the navigation to flag bad fixes; (2) editing each ping of each beam, flagging

outliers, bad data, etc., (3) merging the depth and backscatter data with the cleaned

navigation, (4) reducing all depth values to mean low low water based on predicted tides;

(5) performing additional refraction corrections for correct beam raytracing; (6) separating

out the amplitude measurements for conversion to backscatter, (7) gridding depth and

backscatter at the highest resolution possible with water depth, (8) regridding individual

subareas of bathymetry and backscatter into final map sheets, (9) gridding and contouring

the bathymetry, and (10) generation of the final maps. Nearly finalized maps were

completed aboard ship during the cruise and final maps were completed within one month

of the end of the cruise. Final maps will be published as USGS Miscellaneous

Investigations I-Map Series.
6

EM300 DATA-PROCESSING FLOW DIAGRAM

data telegrams (phase, amplitude, beam number, SVP, navigation

edit navigation

edit beams & bings

merge data with clean navigaton

tide corrections

final refraction corrections

separate out

phase+amplitude depth

determinations

grid depth data into

small map sheets

grid smapp map sheets

into large bathymetry map

generate shaded-relief map

grid bathymetry data and

generate contours

digitally combine maps

with land DEMs

digitally draft

bathymetry map

separate out amplitude

 (backscatter) data)

grid backscatter data

into small map sheets

grid small map sheets into

 large backscatter map

digitally combine map

with land DEMs

digitally draft

backscatter map

Figure 3. Processing flow diagram used to process the raw Simrad EM300 data

telegrams.
7

The Maps

The large overview maps of backscatter and shaded relief that accompany this report

were generated from large-scale subarea maps. The high-resolution subarea maps were

regridded at the coarsest resoltuion of the subarea sheets within each area. This regridding

reduces resolution in the shallower areas but allows the entire area to be mapped at a

constant grid size. The detailed maps of each disposal site were produced at the maximum

resolution allowable for the data. Both the backscatter and the bathymetry maps were

gridded at the same scale for both the individual subarea (Appendix 2) and for the

overview map. 

The color-coded bathymetric charts represent the more traditional method of displaying

bathymetry. The contours were derived from the gridded, tide-corrected depths. The

resultant contours were smoothed by a 3-point running average in the overview maps, but

are unsmoothed in the subarea maps. Even at the original contour grid, more than 90% of

the data must be discarded so as to only show some chosen contour interval. A much

better representation of bathymetry, using 100% of the data is a shaded-relief map.

A shaded-relief map (Fig. 4) is a pseudo-sun-illumination of a topographic surface

using the Lambertian scattering law (equation 1), where B is the pseudo-sun brightness, I

is the maximum brightness, and Φ is the angle between the pseudo sun and a normal to the

bathymetric surface.

B = I(cos Φ) (1)

The backscatter map (Fig. 5) is a representation of the amount of acoustic energy, at 30

kHz, that is scattered back to the hull-mounted receiver. Backscatter can be thought of as

albedo; that is, the actual reflectance of the seafloor to 30-kHz sound. The Simrad EM300

system has been calibrated at the factory (to an rms pressure referenced to 1 μPa at 1 m

from the transmitter) and all gains, TVGs, etc. that are applied during signal generation and
8

detection are recorded for each beam and removed from the backscatter amplitude value

prior to recording. Consequently, the backscatter can be calibrated to an absolute

Figure 4. Preliminary, shipboard-produced shaded-relief map of north Maui and Maui

Channel. Artifical sun is at azimuth of45 ̊ and an elevation of 45 ̊. The data were gridded

at 20-m spatial resolution. The fuzzy dark stripes are the outer-beam artifacts shown in

closeup in figure 6 and discussed in text. compart with Figure 5.

reflectance of the seabed . However, the amount of energy, measured in decibels (equation

2), where I1 is the measured backscattered amplitude and I2 is the reference pressure of 1,

is some

dB= 10log (I1/I2) (2)

complex function of constructional and destructional interference caused by the interaction

of an acoustic wave with a volume of sediment (Gardner et al., 1991) or, in the case of

hard rock, the seabed. The backscatter from the EM300 from a sedimented area represents

volume reverberation to at least 10 cm subbottom depth caused by seabed and subsurface

interface roughnesses above the Rayleigh criteria (a function of acoustic wave length),

volume inhomogenieties larger than about half the wavelength (2.5 cm), the composition
9

of the sediment, and its bulk properties (water content, bulk density, etc.). Although, it is

not yet possible to determine a unique geological facies from the backscatter value,

reasonable predictions can be made based on the local geology of the islands.

It can not be stressed too strongly that one of the great advantages of this survey is that the

bathymetry is completely georeferenced with the backscatter. That means that each pixel

on the map has a latitude, longitude, depth, and backscatter value assigned to it.

Figure 5. Preliminary, shipboard-produced backscatter map of north Maui and Maui

Channel. Light areas represent high backscatter. The data were gridded at 20-m spatial

resolution. The data holidays (gaps) were surveyed in the final version. Compare with

Figure 4.

Cruise Daily Log

The following is a daily log of noteworthy events during the cruise. All times are local

standard Hawaii time (GMT-10) and designated as “L”. The ship arrived in Honolulu on

January 28. All computer equipment were loaded on January 28 and set up with the usual

minor problems. All the computer networking, etc. were completed on January 29.

Customs presented a problem because the ship is registered Canadian (considered foreign
10

by US Customs), and the crew are Canadian and Philipino. The scientific staff included

two Norwegian, several Canadian, and several US citizens. US Customs dictated that we

could not depart until all souls were cleared; clearance was expected to take a day or two.

In addition, we could not get a slot at the fuel dock until 1000 Friday January 30.

However, we still had two major problems. Firstly, both engines on the starboard shaft

(twin screws, variable pitch props) were down and the Chief Engineer could not determine

the problem. Secondly, after being allowed to run some patch tests in Mamala Bay on

January 29, it was determined that we have +50 dB noise from the ship. A series of noise

tests, shutting down mechanical systems one by one, did not isolate the cause of the noise.

The EM300 is only getting ~3 x water depth in 1500 m of water although the data look

good. The C&C group continued to investigate the noise problem while we awaited our

slot at the fuel dock. Some of the noise (~10 dB) was eliminated by properly grounding

the UPS on the clean electrical circuit. The remaining noise (~37 dB) is suspected to be the

result of the combination of the required pitch/rpm required to push us along at 8 to 10 kts.

Mechanical noise, cavitation, and resonate beating of the two propellers are suspects.

Friday, January 30 (JD 30)

We completed fueling at 1700 L but the Simrad engineers encountered a potential

problem with the transducer depth offset. We spent another 5 hours at the fuel dock testing

depths with a lead line. Everything worked out to be a non problem and we departed the

fuel dock at 2200L and began collecting data.

Survey Line 0 was designated as the southern-most line run during the patch test. Line

1 was a no-data line and Line 2 began at the eastern end of Line 0.

Saturday, January 31 (JD 31)

We ended Line 4 two-thirds the way along the line at ~0830L so that we could run a

squat test (the change in ship draft versus ship speed) during daylight while Mike Field
11

was stationed on Diamond Head with the differential GPS reference station. We were

back to running survey lines at 1300L with three engines on line.

There continued to be lots of vexing Simrad problems involving yaw corrections, some

strange motion artifact, and a one-ping delay between the depth information in the data

telegram and the backscatter information. This last artifact shows in the data as a series of

track-normal noise stripes. The Simrad personnel are trying to track the problem.

Sunday, February 1 (JD 32)

The Pearl Harbor Port Authorities would not allow us to go inside the restricted zone of

submarine buoys so the area west of the harbor entrance was not surveyed. However, we

did get permission to survey the Honolulu harbor entrance restricted zone. Bugs continued

to show up in the Simrad software but the Simrad folks and JHC continued to run them

down and fix them. Our survey speed settled down to about 9.5 kts but the swath width

was less than advertised or hoped for. 

This day was spent surveying the shallowest area off south Oahu so that obstacles

(coral reefs, small sail boats, jet skiers, swimmers, etc.) could be seen in daylight and

avoided.

Monday, February 2 (JD 33)

Routine day of surveying the east Oahu margin. We also ran two survey-normal lines

for system calibration and also to see what ranges and modes were appropriate for deep

water. We got to 3200 m water depth and were getting 4500-m swath in the very-deep

mode. We determined that in water depths <50 m we should run in very shallow mode, at

50 to 200 m we should be in shallow mode, at 200 to 700 m we should be in medium

mode, 700 to 2200 m we should be in the deep mode, and at depths > 2200 m we should

be in the very deep mode (Table 4).
12

Tuesday, February 3 (JD 34)

We completed the survey of the east slope of Oahu then moved back to the south slope

to fill in small holes. Also, it was discovered that the Simrad data telegrams got scrambled

at times where one telegram would have the correct depth information but would contain

the previous telegram's amplitude data. The scrambling appears to occur when the system

goes into very shallow water (<50) and then back into deeper water. It turned out that all of

our Gulf of Mexico shallow-water areas and our shallow-water south Oahu data have the

problem of mismatched datagrams. Pablo Mejir (of C&C Technologies, Inc.) successfully

wrote some software to unscramble the data telegrams and no data were lost. 

We spent most of the day running a tighter grid of survey lines over the south Oahu

ocean disposal site so as to have the best possible survey for the USCOE and USEPA.

We then finished up the day running lines along our southern boundary.

Wednesday, February 4 (JD 35)

We completed the Oahu survey at 0900L and transited to a point outside Honolulu

harbor. A water taxi arrived at 1000L to take off James Chance, John Hughes-Clarke, and

Mike Torresan and bring aboard Luciano Fonseca (an OMG graduate studentFinally, at

1300L we cleared US Customs and departed the Oahu area. Weran a westward line

towards deep water and Kauai. Once around Barbers Point, the southwest end of Oahu we

hit 15-ft swells and 30 kt northwesterly winds. The wind and swell slowed us down

because we had to head directly into them. We made a dogleg track so that the remaining

Simrad engineer could determine how deep the EM300 would produce usable data.

Certainly, at 3500 m we were still getting reasonable data but by 4000 m the data were

pretty dirty.

We arrived at the beginning of the Kauai survey at 2300L and immediately began to

collect excellent-quality data. The swell was modest and the winds died down to <20 kts.
13

Thursday, February 5 (JD 36)

We surveyed the Kauai area and halved the line spacing over the two Kauai ocean

dump sites. We spent considerably more time on the Kauai survey because we had to put

off the remaining Simrad engineer at Port Allen at 1000L on Friday. We spent the day

completing the planned survey, filling in data gaps, and then extended the survey to the

south because we had already surveyed the reef front in shallow water. 

It appears that in the deep-water mode the TVG for the amplitude data is somehow

different than in the medium mode. We see the mean level of the backscatter (mean DN)

is lower in the deep-water mode than in the medium mode. This can be corrected during

post-cruise processing.

Friday, February 6 (JD 37)

The Kauai survey was completed at 0900L so that the Simrad engineer could

disembark by the work boat to Port Allen. The work boat was back aboard by 1030L .

However, we were warned that the Pacific Missile Range was conducting naval operations

with surface missile launches and the direct passage to the northern slope of Niihau, our

next survey area was restricted. Consequently, we were forced to transit south of Niihau

and begin the Niihau survey on the southwest corner of the island. We steamed at full

speed, rather than survey speed, to make up for the added distance of our new transit. We

begain the Niihau survey at 1330L The Niihau survey was run for Monterey Bay

Aquarium Research Institute (MBARI) in exchange for them running the USGS Hilo

survey. The exchange saved both groups about 36 hours of non-productive transiting

between the island chain.

Saturday, February 7 (JD 38)

The Niihau survey continued throughout the day. The EM300 was able to collect

excellent-quality data (i.e. good bottom detect) in 4200 m but it must be emphasized that
14

sea conditions were calm and the bottom was highly reflective (<-20 dB). The Niihau

survey was completed at 2330L and we commenced our eastward transit to Maui. The

transit lines were layed out so that they added a south line to our existing surveys at Kauai

and Oahu. An additional line was collected for MBARI between Niihau and Kauai

Sunday, February 8 (JD 39)

We transited all day, making our way to the northwest Maui area. We positioned a

transit line along the north side of Molokai to establish a base line for the MBARI survey

in this area. After we completed the baseline, we continued to the northwest Maui area.

Monday, February 9 (JD 40)

We arrived in the north Maui area and began the survey at 0130L, running the shallow

lines first, then working out into deeper water. The day was routine with the only surprises

being large pods of whales flopping all over the sea surface. It was quite a sight. We had a

slight problem with the Simrad system not accepting the sound velocity data. The

consequences were that the system did not automatically ray trace the individual beams.

Luckily, my OMG processing software allows for this problem and I was able to correct

the problem. I then went back over the data collected to date and discovered the problem

had persisted throughout the cruise. Consequently, I looked at the data from the previous

surveys and found the same problem with the Oahu data so I reprocessed the Oahu data set

and backed up the new data on the magneto-optical archive disk.

Tuesday, February 10 (JD 41)

We broke off our survey line at 0930L to steam to the buoy off Kahalui, Maui to

change out L. Fonseca and bring aboard H. Tianhang. The purpose of taking the time to do

this changeout was to give the graduate students at the Ocean Mapping Group valuable

experience at sea with a high-resolution multibeam mapping system. We anticipated the

changeout taking only one hour. However, because we were required by U.S. Customs to
15

provide additional documentation for clearence, we did not leave until 1400 L. We

continued surveying the north Maui area throughout the day without further incident.

At 2055 L the Simrad EM300 stopped pinging. No warning, it just stopped. The

system was rebooted and came right back up by 2125 L. The cause of the crash remains

unknown. Refraction has become a big problem in the region north of Maui. The Sea

Bird CTD and frequent XBT drops allows the Simrad software to correct for refraction for

awhile, but then, within a mile or so, severe refraction creeps back into the data. This

problem will have to be corrected during post-cruise reprocessing.

Wednesday, February 11 (JD 42)

Refraction in the north Maui area continued to plague the data and it will require a

major effort in post-cruise processing to fix each ping. A problem cropped up early in the

morning with the battery charger in the Simrad transducers. The battery has been drained,

possibly from a short or from a bad UPS. Art Kleiner reset the UPS and everything

appears to check out fine. Simrad was called and offered no suggestions.

The cable of the Sea Bird CTD winch got all twisted and caused an hour delay while it

was untwisted and reterminated. There is a continuing problem with the Simrad rejecting

the Sea Bird CTD data but it is accepting XBT data. The effect is to not automatically

compensate for acoustic refraction but my OMG software is handling it. 

A major problem surfaced today with the Simrad EM300. The outer yaw-steering

sectors on both sides appears to not be performing correctly. The bathymetry in the outer

beams has a 2 to 5-m shift across both outer sectors (port and starboard) relative to the

middle sectors (arrows in Fig. 6). The shaded-relief images show dramatically show the

artifact. The C&C programmers are puzzling over the potential causes.
16

Figure 6. Close-up view of shaded-relief image showing depth artifacts created by

the outer-beam sectors not correctly compensating for ship yaw.
17

Thursday, February 12 (JD 43)

The outer-sector problem persists. All of the north Maui area deeper than about 200 m

shows the strong depth offset. At the suggestion of John Hughes-Clarke, we turned the

power to the Simrad system off, then back on, and then rebooted. This may solve the

problems we were having with the bad yaw-stearing sectors. The entire north Maui dataset

will have to be reprocessed with a sector fix. We completed the north Maui area at 1100L

but did not go back to resurvey the area with the bad sector steering. We immediately

commenced to map the Maui Channel area.

The problem with the battery backup for the Simrad system continues to plague us. The

battery is at the verge of being completely discharged, thereby giving us no emergency

power for an orderly shutdown should the ship's power go out. In addition, the water

column appears to be changing rapidly, causing a lot of problems with refraction

corrections. We are taking several XBTs each day but are now running low on XBTs. We

have enough for only three launches a day until the end of the cruise.

Friday, February 13 (JD 44)

Awoke this morning to the biggest crisis yet. The galley has run out of coffee filters,

so they stopped making coffee! We showed them how to use paper towels for filters until

we can get an emergency supply in Honolulu on the 15th at the Chief Mate exchange. We

continued to have the problem with the outer beams of the DTM files giving a 1 to 3 m

height offset (Fig. 6). No resolution yet.

Saturday, February 14 (JD 45)

Today we got a phone call from the Coast Guard relaying a public inquiry from citizens

on Maui with regard to the nature and possible impacts of our survey, especially

concerning the safety of whales, distance restriction from whales, and dumping sewage

and garbage. I called the Coast Guard and provided them with an explanation of our
18

mission, which apparently satisfied the public concerns. We received another call from the

Coast Guard an hour after the first one asking additional questions about what we were

doing and our conversation satisfied them that we were OK. They inquired about why

there was no Notice to Mariners about our operations and I informed them that C&C had

contacted the Coast Guard in Honolulu and spoke to a Mr. Dick Spears. Mr. Spears was

given the dates, type of operations, the ship, etc. and he elected not to place the information

in Notice to Mariners. That explanation also satisfied the Coast Guard.

We completed the Maui Channel (Poilolo Channel) at 2200L. We transited through the

Lanai area (Auau Channel) and commenced mapping at 2330L the Kahoolawe area

(Kealaikahiki Channel). 

Sunday, February 15 (JD 46)

We broke off mapping in the Kahoolawe area at 0600L to transit to Honolulu for the

exchange of Chief Mates. While on the transit to Honolulu I received a phone call from a

Mr. Honda of the NMFS. He inquired as to whether we had specific permission to operate

in the Humpback Whale National Marine SanctuaryI suggested he contact Mr. Allen Tom

of the NOAA National Marine Sanctuary Program, Kihea, Maui. I had informed Mr.

Tom in Nov. ‘97 of our cruise and he was enthusiastic about our objectives. I also

informed Mr. Honda of my visit to Silver Springs where I informed all the NOAA

Sanctuary people of our intent to map the Hawaiian sanctuaries. He said he would "get

back to me before 1500L

At 1400L I received a conference phone call from the Coast Guard, Kihea that included

Allen Tom (NOAA Office of Marine Sanctuaries), Gene Nita (NMFS), Dick Honda

(NMFS), and Emily Gardner (State of Hawaii). They asked questions concerning towing,

power, power dropoff, and frequency. Finally Ms Gardner asked if it was possible for the

ship to alter course if we came within 100 yds of a whale. Evidently, we were surveying

during the prime whale-mating season. In addition, she was worried about small cetaceans
19

and dolphins. I gave a standing order to the Captain (who was in the ship’s office with me

during the call) that the ship was to alter course at any time so as to stay at least 100 yds

away from any whale or small cetacean. All those on the conference call heard my order

and it seemed to satisfy them. After a 20 minute conversation, I received permission from

them to continue our survey.

We did not get back to the survey line until 1800L. We commenced to map in the

Kahoolawe area and immediately saw the yaw-steering sector artifact in the C&C display.

We were now convinced there is a problem with the yaw-steering sectors. The artifact

occurs whether or not we have yaw steering activated or off.

Monday, February 16 (JD 47)

We continued to map in the Kahoolawe area. The outer-sector problem continued to

perplex us, Simrad in Norway, and C&C in Lafayette. Email and faxes have been passed

back and forth, but no apparent solution has been suggested. At 1000L we hove to and ran

an exhaustive noise test on the ship. We powered down everything except the emergency

generator (still have >45 dB vs the ~37 dB we measured off Oahu during our Oahu trials

under similar conditions, then turned off the emergency generator and went on one

generator (still at >45 dB), etc. 

A circuit board fried in the Simrad system when it was powered back up. The Simrad

ethernet connection is not operating so that there is no communications between the Simrad

system and the data-acquisition system. Consequently, we could not collect data. This

posed a major dilemma; C&C do not carry spares because of the expense. By 1400L the

C&C boys located a breaker that had tripped off when we powered the ship down for the

noise test. When the breaker was reset, the Simrad system came right back up. We were

back on line and collecting data by 1430L.
20

I discovered, while trying to clean up some data stored on my backup MO drive, that

my MO drive can not read directories and files off of the MO disks. I fear it is because of

the dirty non-filtered air that is being pumped into the lab. All the computers and

keyboards are covered with black soot, apparently because outside air is being piped

directly into the lab. This has left me with only two backups; the Exabyte and the DLT,

both of which take several hours to backup files. 

Tuesday, February 17 (JD 48)

We continued to survey the area north of Kahoolawe and we still have the outer-sector

artifact problem. Nothing eventful occurred all day.

Wednesday, February 18 (JD 49)

We continued to survey the area north of Kahoolawe and we still have the outer-sector

artifact problem. Simrad engineers in Oslo contacted us and have determined that one of

the pc boards in the yaw-sector beam forming might be defective. They will send a

replacement to Honolulu. 

Thursday, February 19 (JD 50)

Today was our first day of overcast skies. The sun didn't really come out until well

into the afternoon. Winds were light and the sea was calm. We continued to survey the

area north of Kahoolawe between Lanai and Maui. The area is shallow (<100 m) and has

taken ~36 hr more to map than anticipated. However, the effort was well worth the time

expended because the maps are spectacular. Several platform reefs, numerous pinnicle

reefs, terraces and fields of patch reefs are clearly evident. 

We were continued to be puzzled by the strange outer-sector artifact. The C&C

display, contoured at 0.1 m (showing color-coded raw data) does not show much of

anything one would call an artifact. The outer beams are a little shabby, but there is no

mismatch, depth offset, or linear trend. However, I see the artifact in the processed
21

shaded-relief and contour data. Two facts we know: (1) the Simrad engineer Kjell Nilsen

decreased the outer-sectors TVGs just as he departed the ship after mapping Kauai; and (2)

our artifacts showed up the first surveyed flat area (north Maui) after Kjell left the ship. It's

hard to determine anything from the Niihau and Kauai surveys because nothing is flat in

those areas.

It could be that the EM300_Beam_Weight_Mask file that gets used by the -

custom_weight) flag of the weigh_grid program in the JHC software needs to be adjusted

for the new TVGs that Kjell tuned in? Might this be why we see the artifact and the C&C

boys don't? When I contour a flat area at 3-m contour interval I see the artifact in the

contours, yet the C&C display does not see it at 0.5 m contour interval. However, C&C

does not process the data, but rather, they simply take a mean value for each beam and grid

that value. This method effectively smoothes the variance and this probably explains why I

see the artifact and they do not.

Friday, February 20 (JD 51)

Another cloudy day but calm seas. The Kahoolawe area was finally completed at

0330L. We were immediately poised to begin the Lanai area, a vast stretch of area between

the islands of Lanai and Maui all less than 100-m deep. 

Saturday, February 21 (JD 52)

The winds in Auau Channel were 30+ kts throughout the morning and picked up to 35

kts in the afternoon, causing a local chop that made things uncomfortable for awhile. The

mapping was unaffected by the ship motion. The winds continued all day and into the

night.

The Captain and/or Chief Engineer were adjusting ballast this afternoon and evidently

did something unusual because we suddenly acquired a ~10° list. When I inquired about

the list, I was told we didn’t have the appropriate ballast for our light fuel load.
22

Sunday, February 22 (JD 53)

The winds in Auau Channel increased during the night and by day break were

sustained at 50 kts and gusting to 70 kts. Evidently, some local disturbance created all this

wind although the National Weather Service forcast only 25-kt winds. The ship is very

light on fuel and the winds heal us over >15° when on our beam. We changed the

orientation of our survey lines from NNW-SSE to more N-S so that we would be either

heading directly into the wind or have it on our stern. This made the ride more comfortable

and kept us from rolling too much. The data continue to be good. 

In the early afternoon the Captain and Chief Engineer began to be disturbed by our lack

of ballast on the starboard side because of low fuel load. By late afternoon they voiced

concern about running out of fuel before we could complete our survey. After dinner the

Captain summonsed Art Kleiner to his cabin and informed him that we would have to

head for Honolulu at 2100L because of his concern for lack of fuel, ballast, and the heavy

seas between Molokai and Oahu. The Captain terminated the survey at 2100L. We did not

complete the Auau Channel survey during this cruise (although C&C Technologies

appreciated the problem and completed the survey in mid March at no additional cost). We

ran a line north to the lee side of Molokai, then proceeded collecting data along the south

coast of the island and then plowed our way to Honolulu.

Monday, February 23 (JD 54)

We arrived at the Honolulu buoy at 0130L (instead of the planned 1000L) and waited

until the pilot arrived at 0800L and tied up to the fuel dock by 0900L. A summary of the

cruse statistics is shown in Tables 4 and 5.
23

Table 4. Time spent on each survey area

Oahu 1/321 to 2/4/0900L 3.5 days

Kauai 2/4 2300L to 2/6 0900L 1.4 days

Niihau 2/6/1330L to 2/7 2330L 1.5 days1

North Maui 2/9 0300L to 2/12 1100L 3.2 days2

Maui Channel 2/12 1100L to 2/14 2200L 2.5 days

Kahoolawe 2/14 2330L to 2/20 0330L 4.5 days3

Lanai 2/20 0330L to 2/22 2100L 2.7 days

____________

1 Surveyed for MBARI in trade for them surveying NE Hawaii (Hilo) area to save transits

2 Does not include 4.5 hr transferring people at Kahului, Maui

3 Does not include 12 hr exchanging Chief Mates in Honolulu

Table 5. Cruise statistics

Average speed .......................10.3 kts

total line kms ....................... 5800 km

total area mapped................2800 km2

days at sea........................... 22.5.days

days mapping ..................... 19.3 days

patch test ...................................1 day

transits .................................. 2.2 days

References Cited

Gardner, J.V., Field, M.E., Lee. H., Edwards, B.E., Masson, D.G., Kenyon, N., and Kidd,

R.B., 1991 Ground truthing 6.5-kHz sidescan sonographs: What are we really

imaging?. J. Geophys. Res., v.96, p. 5955-5974.

Hughes Clarke, J.E., Mayer, L.A., and Wells, D.E., 1996, Shallow-water imaging

multibeam somars: A new tool for investigating seafloor processes in the coastal

zone and on the continental shelf. Marine Geophysical Researches, 18: 607-629.
24

Appendix 1. Details of Simrad EM300

RX

sample rate: 4509 Hz

Bandwidth: 5000 Hz

Demod. frequency: 32565 Hz

TX

Power reduction 10 dB, 20 dB

Mode-dependent parameters:

Parameter/Mod

e

Very Deep Deep Medium Shallow Very

Shallow

Depth Range 1000-5000 m 500-3000 m 100-1000 m 30-300 m 5-50 m

Pulse length 5 MS 5 MS 2MS 0.7 MS 0.7 MS

Delay between

TX pulses

24 samples

5.32ms

24samples

5.32 ms

12 samples

 2.66 ms

5 samples

1.11 ms

5sample

s

1.11 ms

TX pulses

TX frequency

beam angle

(positive angles

to port)

31 44° 1

32.5 31.5° 3

34 20.5° 5

32 -10° 7

33.5 0° 9

30.5 -10° 8

33 20.5° 4

31.5 -31.5° 4

30 -44° 2

31 69° 1

32.5 48° 3

34 33° 5

32 17° 7

33.5 0° 9

30.5 -17° 8

33 -33° 6

31.5 -38 4

30 -69° 2

31.5 60° 1 33

0° 3 30 -60°

2

31.5 60° 1 33

0° 3 30 -60°

2

31.5

60° 1

33

0° 3 30

-60° 2

Estimated max

SL

240/234 dB

(1°/2° beam)

238/232 dB

(1°/2° beam)

230/dB

(2°beam)

224 dB

 (2° beam)

RX/TX

Beamwidth

1° or 2° 1° or 2° 1° or 2° 2° 4°

Manually

selected RX

sector width

98°, 80°, 64° 150°, 140°,

128°, 114°,

98°, 80°, 64°

150°, 140°,

128°, 114°, 98°,

80°, 64°

150°, 140°,

128°, 114°,

98°, 80°, 64°

150°,

140°,

128°,

114°,

98°, 80°,

64°

BSP bandwidth

(for beams

close to normal

incidence)

200 Hz

(350 Hz)

200 Hz

 (350 Hz)

550 Hz

(1000 Hz)

1000Hz 1000 Hz

RX beams 135 135 135 111 111
25

OUTPUT

SAMPLE

RATE

563 HZ 1127 HZ 2254 HZ 4509 HZ 4509 HZ
26

Appendix 2. Grid sizes for subarea sheets and overview maps for each survey area.

area subarea sheet grid size overview map 

Hawaii ................... area 1..........................30..........................30

Kahoolawe ............. area1............................5..........................20

area2..........................10

area3..........................20

Kauai.......................................................................................20

area0..........................10

area1..........................10

area2............................5

area3..........................10

area4..........................20

area5..........................20

area6..........................20

Lanai....................... area0............................5

Maui ........................................................................................20

area0............................4

area1..........................10

area2..........................20

area3..........................10

area4..........................20

area5..........................10

area6............................4

area7..........................20

area8..........................20

Maui Channel.........................................................................30

area0..........................10

area1 10

Oahu........................................................................................30

area0.........................5

area1.........................5

area2.........................5

area3.........................5

area4.........................5

area5.........................5

area6.........................5