Laurent THERY Douglas CHARLEY Michel LARDY Joseph TARI Bathymétrie du lac Létas Ile de GAUA (Banks) (Vanuatu) GEOLOGIE-GEOPHYSIQUE No10 SCIENCES DE LA TERRE terre, océan, atmosphère

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Bathymétrie du lac Létas Ile de GAUA (Banks)

(Vanuatu)

Laurent THERY Douglas CHARLEY

Michel LARDY Joseph TARI

terre, océan, atmosphère

NOTES TECHNIQUES

SCIENCES DE LA TERRE

GEOLOGIE-GEOPHYSIQUE No10

INSTlTUT FRANCAIS DE RECHERCHE SCIENTIFIQUE POUR LE DEVELOPPEMENT EN COOPERATION

Document de travall

REPRÉSENTATION DE L’ORSTOM EN RÉPUBLIQUE DU VANUATU

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Date de la mission : 03/11/94 au 15/11/94

Matériel utilisé : Bateau pneumatique (Bombard) écho sondeur JFC 46

GPS (Trimble Navigation TRANSPARKII GPS)

Corrections des données à l’aide du logiciel GEOCAL

Les données récupérées par le GPS (Global Positioning System) sont lues dans la norme WGS84. Les positions absolues données par les cartes IGN éditées dans les années 60 sont mauvaises, et il convient donc de corriger les valeurs fournies par le GPS pour les replacer sur les cartes IGN selon le réferentiel de l’époque : Mercator Transverse Universel (MTU), fuseau n”58, méridien d’origine 165” Est du Méridien International.

C’est à partir du logiciel “GEOCAL” que nous réalisons ces transformations. Dans le tableau “mesureskésultats”, les données de terrain sont les colonnes GPS et les données corrigées sont les colonnes

“Bellevue” (cf tableau).

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CARTE DU VANUATU

0

TORRES 'po,

C

Gaua ~5

Maiakula

/ : 13 =-r.Omango . . - - -

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CARTE DES PROFILS

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TABLEAU “MESURES / RESULTATS”

LATITUDE HAUTEUR

Bellevue

14 16,136 14 15 54 035,

14 16,35 14 16 07 1

14 15.804 14 15 34 1

Bellevue 167 30 24 167 29 38 167 29 47 167 29 48 167 29 49 167 29 51 167 29 58 187 32 31 167 29 26 167 29 49 16i 32 31 167 29 38

14 16,4 114 16 10 I 11

14 16,32 14 16 05 1

14 15,63 14 15 24 1

14 16,272 14 15 02 1

14 17,213 14 16 59 1

14 16,164 14 15 56 2

14 16,407 14 16 10 2

14 17,212 14 16 59 2,5

14 16,322 14 16 06 3

14 16.35 14 16 10 3

1167 30,231 '167 29 48 167 29 48 167 29 30 167 29 48 167 29 51 167 31 07 167 32 26 ,167 30 32 167 30 47 167 30 57

!167 37 07 ,167 29 30 167 29 36 167 29 41 167 29 46 187 29 57 1167 30,125

1167 30,823 167 30 23 167 30 54 167 30 58 1167 31,606 167 31 10

14 17,848 14 17 37 5

14 15,51 14 15 17 5

14 15,37 14 15 08 5

14 17,183 14 16 57 5

14 16,276 14 1s 02 6q

167 32 42 167 29 35

167 29 40 14 16.376 114 16 09 6

14 17,249 114 17 01 6

14 16,345 114 16 07 7

14 16,235 (14 16 00 10

14 15,885 14 15 39 10

14 16,212 14 15 59 10

14 15,728 14 15 30 10

14 16.066 14 15 50 10

167 32 40 167 29 40 167 29 '37 167 29 46 1167 30,361 167 29 56

14 17,845 114 17 37 ! 14 15.39 114 15 10 l 167 31 09

il67 31 19 14 16,706 14 16 29 10

14 18,4 14 18 10 10

14 17,182 14 16 57 10

~167 31 28 1167 32 40

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(167 30,151 il67 29 43 114 16,224 114 16 00 151

167 30,201 !167 29 46 114 15,905 14 15 40 15

167 30,351 1167 29 55 14 16,19 14 15 58 15

167 30,451 1167 30 01 14 15,745 Il4 15 31 15

167 31,583 il67 31 09 14 15,474 114 15 15 15

167 31,821 1167 31 23 14 76,724 (14 16 30 15

167 33,056 1167 32 37 14 17,28 14 17 03 15

167 30,161 1167 29 44 14 16,152 14 15 57 20

167 30,173 1167 29 49 '14 16,177 14 15 43 20

1167 30,251 1167 29 54 114 15,952 114 15 56 1 201 167 30,331 1167 30 04 14 16,17 114 15 33 1 20

167 30,504 1167 30 32 14 15,77 (14 15 49 20

167 30,971 1167 31 01 114 16,04 114 17 37 20

167 31,451 116'7 31 07 14 17,843 (14 15 11 20

167 31,553 il67 31 08 14 15,42 114 15 12 20

187 31,563 1167 31 19 14 15,423 14 16 18 20

167 31,742 il67 31 23 14 16,531 14 16 33 20

167 31,821 1167 31 26 114 16,784 14 18 09 20

187 31,874 /167 31 28 14 18,374 14 18 10 20

167 31,901 1167 32 37 14 18,4 14 17 03 20

167 33,042 1167 29 44 14 17,294 14 15 55 20

167 30,205 1167 29 46 14 16,003 14 15 46 23

167 31,379 (167 30 58 14 17,926 14 17 42 23

167 30,331 .j167 29 54 14 16,Ol 14 15 53 25

187 30,531 1167 29 54 14 15,786 14 15 47 25

187 30,836 767 30 06 14 16,099 14 15 33 25

187 31,561 167 30 24 14 15,363 14 15 52 25

167 30,555 ,167 30 07 14 15,81 14 75 35 30

167 30,852 il67 30 25 14 16,03 14 15 48 30

167 30,982 !167 30 33 114 16,04 14 15 46 30

167 31,426 167 31 00 14 17,929 14 17 42 30

167 31,447 ,167 31 01 14 15,441 14 15 13 30

1167 31,478 il67 31 02 114 17,848 114 17 37 301 167 31,589 1167 31 09 114 15,493 114 15 16 30

167 31,715 1167 31 17 14 16,486 114 16 15 30

167 31,801 1167 31 22 '14 18,301 (14 18 04 ' 30 167 32,018 1167 31 35 114 18,339 114 18 06 30 167 33,003 il67 32 34 14 17,33 114 17 06 1 30 167 33,013 1167 32 35 14 .17,173 114 16 57 30

167 30,461 (167 30 02 114 15,932 14 15 42 31

167 30,532 1167 30 06 114 15,864 14 15 38 32

167 30,888 il67 30 27 114 15,919 14 15 41 33

167 31,564 1167 31 08 114 15,442 14 15 12 33

167 30,601 1167 30 10 114 15,815 14 15 35 35

167 30,621 il67 30 11 114 15,828 114 15 36 40

167 30,661 1167 30 14 114 15,782 14 15 33 40

167 30,856 '167 30 25 il4 15,907 14 15 41 40

167 30,976 !e167 30 33 114 15,986 14 15 45 40

;167 31,478 il67 31 03 il4 17,978 (14 17 45 40

167 31,505 !167 31 04 114 17,86 114 17 38 40

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167 31,591 il67 31 09 14 15,503 il4 15 16 4a

167 31,762 il67 31 20 14 18,262 114 18 02 40

167 31,832 1167 31 24 14 16,241 114 16 01 40

167 32,041 il67 31 36 14 18,288 114 18 03 40

167 32,951 1167 32 31 14 17,366 114 17 06 40

167 30,891 il67 30 27 14 15,944 114 15 43 44

167 30,691 ;167 30 15 14 15,804 114 15 34 50

167 30,858 il67 30 25 14 15,99 114 15 46 50

167 30,981 1167 30 33 14 15,971 114 15 44 50

167 31,504 1167 31 04 14 18,007 114 17 47 50

167 31,564 1167 31 08 14 17,895 114 17 40 50

167 31,591 1167 31 09 14 15,516 114 15 17 50

167 31,729 il67 37 18 14 18,224 114 18 00 50

167 31,833 il67 31 24 14 16,168 il4 15 56 50

167 31,961 il67 31 32 14 16,792 114 16 34 50

167 32,051 1167 31 37 14 18,241 114 18 01 50

167 32,772 1167 32 20 14 17,422 (14 17 11 50

167 32,921 1167 32 29 14 17,38 Il4 17 09 50

167 31,642 1167 31 13 14 18,115 Il4 17 53 52

167 31,701 1167 31 16 14 18,179 114 17 57 52

187 30,872 1167 30 14 14 15,86 114 15 38 55

167 31,556 !167 31 07 14 15,495 114 15 16 55

167 31,574 il67 31 08 14 18,06 (14 17 50 58

167 30,731 .jl67 30 18 14 15,82 14 15 35 60

167 30,907. 1167 30 28 14 15,745 14 15 31 60

167 30,968 il67 30 32 14 15,975 114 15 45 60

167 31,593 il67 31 10 14 15,527 (14 15 18 60

167 31,628 !167 31 12 14 17,909 114 17 41 60

167 31,825 1167 31 24 14 16,028 114 14 48 60

167 32,011 il67 31 35 14 16,808 /14 16 35 60

167 30,808 1167 30 23 14 15,952 (14 15 43 62

167 32,056 !167 31 37 14 18,282 114 18 03 68

167 30,972 il67 30 32 14 15,988 114 15 45 70

167 31,587 il67 31 09 14 15,558 114 15 20 70

167 31,592 '167 31 10 14 15,546 114 15 19 70

187 31,707 Il67 31 16 14 17,845 j14 17 37 70

167 31,825 il67 31 24 14 16,016 114 15 47 70

167 32,042 ,187 31 37 14 16,838 il4 16 36 70

167 32,923 ,167 32 29 14 J7,209 114 16 59 / 70

167 30,972 '167 30 32 14 15,946 114 15 43 75

167 32,058 1167 31 37 14 18,166 114 17 56 75

167 30,973 '167 30 32 14 15,907 114 15 41 77,3

167 31,553 167 31 07 14 15,559 !14 15 20 80

167 31,682 .167 31 15 14 16,Ol 114 15 47 60

167 31,715 ,167 31 17 14 16,22 114 16 00 80

167 31,751 167 31 19 14 17,888 114 17 39 1 80 167 32,058 167 31 37 14 18,132 ii4 17 54 j 80

167 32,857 167 32 25 14 17,434 il4 17 12 80

167 32,862 167 32 26 14 17,199 114 16 58 80

167 31,587 167 31 09 14 15,584 ii4 15 21 83

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167 31,774 167 31 20 14 17,88 114 17 39 83

167 32,067 ,167 31 38 14 18,062 j14 17 50 85

167 32.078 :167 31 39 14 16.856 114 16 38 85

167 32,088 167 31 39 14 18,009 ii4 17 47 87

167 32,261 ,167 31 57 14 17,909 Il4 17 41 88

167 31,544 ,167 31 07 14 15,662 il4 15 26 90

167 31.559 '167 31 08 14 15.612 114 15 23 90

1167 31,706 ,167 31 16 114 16,19 il4 15 58 901

167 31,867 ,167 31 26 114 17,869 114 17 38 90

167 32,116 '167 31 41 14 17,995 ;14 17 46 90

167 32.381 :167 31 57 14 17.828 114 17 36 90

167 32,822 ,167 32 23 14 17,138 114 16 54 90

167 31,931 167 31 30 14 17,866 114 17 38 91

167 32.152 167 31 43 14 17.918 114 17 41 91

167 31,986 ,167 31 33 14 17,873 /14 17 39 1 92

167 32,061 ,167 31 38 14 17,83 114 17 36 92

167 32.481 il67 32 03 14 17.736 Il4 17 30 92

167 32,146 '167 31 43 14 17,887 ii4 17 39 93

167 32,582 il67 32 09 14 17,656 114 17 26 93

167 32,774 ,167 32 20 14 17,129 114 16 54 93

167 32,501 ~167 32 04 14 17,056 114 16 50 95

167 32,573 ,167 32 08 14 17,072 114 16 50 95

167 32,697 ,167 32 16 14 17,099 114 16 52 95

167 32,702 ..167 32 16 14 17,473 114 17 15 95

167 32,136 167 31 42 114 17,45 114 17 13 103

167 32.251 167 31 49 114 16.929 il4 16 42 104

I , --.--- I .-.

167 32,269 167 31 50 14 16,938 !14 16 42 1 109

167 32,298 167 31 52 14 16,942 114 16 43 119

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CARTE BATHYMETRIQUE

du

Lac LETAS sur l’ile de GAUA (Santa Maria)

(BANKS)

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Estimation du volume :

L’estimation de volume a été faite de deux manières :

1) de façon empirique, en estimant la surface du lac à chaque hauteur (0 m, 10 m, 20 m,...), et en considérant que cette surface reste constante sur une hauteur fixe. La coupe fictive du lac vous donne une méthode d’ approximation selon la figure ci dessous.

---- P -m----m--

\ d

- - - -g5

- ---II

100

\J

(J7

--D-w- --- ,105

avec cette méthode nous obtenons un volume de 853 million de m3

2) la seconde méthode a été de découper le lac en une suite de volume typique (pyramide, coin, tas de sable . ...)

Le calcul donne un volume du lac de 797 millions de m3.

Comme ces estimations donnent des résultats sensiblement équivalents, nous pouvons retenir que :

le lac Letas a une capacité d’environ 800 millions de m3, à + ou - 10% près.

Par comparaison, le barrage de la Dumbea à Nouméa a une capacité de retenue de 625 000 m3

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ANNEXES

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Sonar Principles

An edio sounder is a device which transmits uitrasonic bearns into the water and listens for echoes. Each beam travels down until it hits an abject or the seabed, then retums to the transducer with an echo. The echo appears on your display.

The time taken for the beams to botmce off submerged abjects, the seabed, etc., and retum as echoes is measured. The data is then con- verted into units of depth and cari be shown in many ways such as on an LCD panel.

The frequency of the wave or puise, the transmitting angle of the beam, and the power of the puise itself, alJ play important parts in determining the appearance of the echo traces on the display.

The seabed, schools of fish, seaweed, grass, bubbles, plankton, eu. all send echoes of different strengths. Generally, the seabed sends the suongest echo, while other abjects send relatively weaker echoes.

The JFC-46 distinguishes fish frorn seaweed, grass etc. as the air bladder of the fish is the objea with the most density.

Echo Sounding Astieboatoavelsechoes remrningmtieDansducef areconvenedm wntinuouslyupdate the JFC-463displ~.

Receivingandiden@fing echoesfmmfishcan dependonse~~~ltâcmrs including:

l Species ofhi

l Numberandsizeoffish

l fishdeptibelowtie boat

l Sensifivitylevet gPowerandirequencyof

thesounder

8 Transducerbeamangle .Boatspe,pd

l Watertumulence

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Seabed Conditions

You cari determine a variery of seabed conditions.

Your unit operates at 2CO kHz giving high resolution of bonom detail tith excellent detection of small fish on your display. The beams transmitted from the transducer form a cane-shape of approximately 20 degrees-a good scope when searching for fish.

Echoes appear at the rig2 edge, adjacent to the range scale, and scroll left across your display. Exh time the echo sounder transmits and receives, old echoes shift to the left to make room for the new echoes.

As your vesse1 moves, an Lrage of the bottom contour and fish echoes that you pass, fil1 your disqiay.

l When the seabed is hard and flat like a mirror, only the beam

direccly under the trrsducer is reflected back to the transducer.

This echo appears on your display as a nanow bottom line, characteristic of hard, sandy seabeds.

l When the depth is shailow and the seabed very hard, a second echo cari appear at exactly double the depth of the uue seabed echo.

l When the seabed is soft (a lot of seaweed or muddy), the bottom line on your display appears thicker. This is because the top surface of the weed or mud sends a weaker echo and also waves returnîng to the ua~nsducer may be slighdy delayed.

l When the seabed is made up of coral, wrecks, or rock piles, the irregu1a.r surfaces and various angles of the seabed retum doseiy spaced echoes. The boaom line on your display appears with irregular long tails.

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Specifïcations

General

Display structure Dimensions No. of dots LCD contrast Backhght

Operating modes

KW

Power source Power consumption Dimensions

Weight Waterproofing EM1

‘JFC-46 QQ3e

FT (fèet) FM (fathoms) M (meters) Zoom size Chart speed White line AIarms

Reset aip log Fish symbols Output power Frequency Depth unit Numerical display Water temp.

Boat speed Sensitivity

CollIlt?l3OC3

Transducer connecter Power connecter

STN LCD (blue)

W3.6"~ H: 2.4" (91xGl mm) 80x128

16 levels, with temperature compensation ON/OFF (LCD, Lamp; Panel, no lighting) FISHFINDER mode (Standard mode) BOTTOM COVERAGE mode

NAV (navigation) mode NAV/TEMP window silicon rubber DC. 10.2 to 162 V approx 4.5 W

H: 6 %6” (160 mm), W: 6 ‘/16” (154 IlltR), D: 2 3/16” (56.3 mm) (without bracket) 1.1 lbs (0.5 kg)

U.S.C.G., CFR 46 IEC 945

auto or manual:

10 15 30 60 120 240 480 600 900 5 10 20 30 40 60 80 100 150 5 10 20 40 80 120 160 200 300 2x, 4x, 8x

frefze, l(lO0 ppm), 2(200 ppm), 3(400 ppm) ON/OFF

Shallow, Deep, Fish 0 to 999 units G sizes GO Wmls 200 kHz

feet fathom, meters

3 digits (under 2.0 ft in ideal conditions) 32.0 to 99.9 o F (0 to 37.0 OC)

mph, km, knots (0 to 70) auto or manual (10 levels)

7 pin, Con-X-Ah type 2 pin, Con-X-Ah type

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TRIMBLE NAVIGATION LIMITED

645 North Mary Avenue P.O. Box 3642 Sunnyvale, California 94086

(408) 730-2900 800-TRIMBLE

Telex: 671393 TRIMBLE UW

Trimble Navigation (Japan) Llmited

Mskuhsri Techno Garden D-2 1-3, Nskase. Chiba-Shi Chiba 261-01, Japan

Trlmble Navigation (Europe) Llmlted 1 Trimble House

Meridisn Office Park Osbome Way, Hook

i Hampshire RG27 9HX . United Kingdom *:

Part Number 1809r1, Rev. R

.,a&: ‘,

P- --

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..+-d- .*;, ._. ; ..=

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av.- 1 _ _

. ,.: OCY -

TRANSPAKII

GPS Persona1 Navigator with VO

Operation &

Maintenance Guide

a TrimbleNavigation

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GPS and the TransPakll GPS and the TransPakll

Global Positioning System (GPS)

GPS is a saleMe-based radio navigalion sysicm. Thc syslcm ullimalcly Will be a conslellalion of 21 aclive salellites and 3 spares in orbits around thc earlh. This syslem Will ensure worldwidc operation wilh 24-hour, all-weathcr covcragc. E!ach saMile transmiis data tbal enables GPS rcceivcrs 10 provide precise position and lime.

‘I’runsI+tkll

TheTransPakII GPS Pcrsonal Navigalor isa hand-held, ballery- powcred navigalion system thal receives data from GPS satel- lites and calculates and displays position, velociiy, lime, and navigational information. Three-dimensional fixes are obtained when tracking fowor more satelliles: two-dimensional fixes cari be obtained fmm three satellites plus user-entered altitude.

Satellite Visibility

The TransPakIl receiver rcquires linc-of-sighi acccss 10 thc saMile signals. Hold (he unit level, witi ils inlcmal antenna facing Ihe sky. Avoid placing your hands on or over the antenna when the TransPakII is in operation. GPS naviga- lion signals are similar to lighi, soanything chai blocks lighl Will block or reduce Ihe effcclivencss of the signals, including Lunnels, heavily forestcd areas, eic. The more unobstructed view of the sky you havc, the bciier your TransPakll Will perform.

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CONTROLS and INDICATORS

Interna1 Antenna Mtery Puck or

Extererl DC Adrptor

\ l Rotary Knob

4 L-R b Switch

Antennn Connecter

Neck Strnp

.._. -... -. __ _.

CONTROLS and INDICATORS

Display Screen

TheTransPakII displays information on tbe backlit4-linc LCD screen. The screen contents are dctcrmined by the rotary knob and user-selected options. The best vicwing angle is from directly in front of thc scrccn.

Rotary Knob

This Qosition switch selects the type of operation that thc TransPakII Will perform-for example: “POS” (positioning) operations.

4 L-R b (Left-Ri&t) Switch

This 2-way switch is used to Select items on thc screen (indi- catcd by a flashing box). Momcntarily pressing the switch to thc lcft or right sclects different scrcen itcms.

A +/- v (Increment/Decremen t) Switch

This 2-way switch is uscd to walk through numbers, Icttcrs of the alphabet, or options (as on a list). Momcntarily pressing the switch upward or downward changes the value of the selcctcd item on the screen.

The A +/- v switch is also used as a trigger when the sclected screen item represents an action to be performed (indicated by brackets-<action>).

Both switchcs automatically rcpeat at a rapid rate when hcld on.

This feature cari be used to quickly roll up to high numbers or to scan past many screen items to Select onc farthcr on.

Low Battery

A battcry symbol ( * ) Will blink in thc lowcr right comcr of the screen in all knob positions 10 indicatc a low batlery condition.The TransPakIl should be tumed offand the batteries replaccd or rechürgcd whcn this symbol appcars.

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--..

OTHER PARTS and ACCESSORIES OTHER PARTS and ACCESSORIES

Battery Packs

Two types of battcry packs are currenlly availablc to support specific user rcquircments.

Standard:

Non-rechargeable alkaline battery pack. This pack holds eight AA batteries and provides over 3-1/2 hours of conlinuous operation.

Optional:

Rechargeable nickel-cadmium battery pack. This pack provides over 5 hours of conlinuous operation; it cari be rechargcd in about 16 hours.

Refcr 10 Section 4, Maintenance (page 58), for procedures to rcmovc or inslall baucry packs, recharge thc nickel-cadmium ballcry pack, and rcplacc ballcrics in thc alkalinc battcry pack.

External DC Adapter

This adaplor enables thc TransPaklI to be powercd by an cxtcrnal, 7- 10 32-volt, 5watt DC supply, such as a cigarcttc lighlcr oullcl in your vchicle.

Rcfcr to Section 4, Mainienance (page 58). for proccdurcs 10 rcmove or inslall lhc adapter.

External Antenna Option

An optional externat antenna (part no. T-ANTENNA) with mounling hardware and table is available for stalionary mounl- ing of the receivcr antcnna up 10 75 fect (22 metcrs) from thc TransPakII. The extcmal anlenna cari be mounlcd 10 provide unobstructed satellite covcrage if Lhe TransPaklI must be opcr- ated indoors or in a vehicle. When no1 in use, me antenna connecter dust covcr on lhc TransPakII should be installcd 10 keep the connecter clean.

Other Items

Thc camera-type ncckslrap cari bc attachcd by clipping it 10 thc rings on bath sidcs of thc TransPakll.

Oplional vehiclc mounling brackels arc availablc for the TransPakII.

A conneclor dcsigncd for thc I/O port on lhe TransPakII is included with the unit. Use lhis conncclor whcn fabricat- ing an imerface table.

An opdonal I/O table is available for rhcTransPakl1. This table has a 25-pin conncclor dcsigned for the communica- lions port on a PC.

The TransPaklI includes a floppy disk conlaining ulility programs for waypoim management and data logging.

Thcse prograrns run on IBM-compatible persona1 compulers.

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. . .

COORDINATE SYSTEM

Ml

Typicul POS screen: LAT und LON in DMD format.

11

‘Ijpicul POS screen; LAT and LON in DMS format.

0" N

S 180’

COORDINATE SYSTEM

The TransPakII displays position information either in the Degree, Minutes, Decimal Minutes (DMD) or in thc Degree, Minutes, Seconds (DMS) coordinate systems. Both systemsare latitude/longitude based. The DMS system expresses position in degrees (O), minutes (‘), and (“) to a tenth of a second. The DMD system expresses position in degrees and minutes, with minutes displayed to one-thousandth of a minute in decimal form.

Norlh l’ule

Suuth Pule

v- -4

Longitude East kq$ude West

Creenwich Merldlnn

7

Figure

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Références

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