landsat as a management tool for mapping shallow water habitats in papua new guinea nj quinn p...

8/7/2019 LANDSAT AS A MANAGEMENT TOOL FOR MAPPING SHALLOW WATER HABITATS IN PAPUA NEW GUINEA NJ Quinn P Dal

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Proceedings of the Fifth International Coral Reef Congress, Tahiti, 1985, Vol. 5

LANDSAT AS A MANAGEMENT TOOL FOR MAPPING SHALLOWWATER HABITATS IN PAPUA NEW GUINEAL'IMAGERIE LANDSAT EN TANT QU'INSTRUMENT DE CARTOGRAPHIEEN EAU PEU PROFONDE EN PAPOUASIE-NOUVELLE.GUINEE

rl.J. QUrrilFlsheries Department, Papua New Guinea University of Technology, Lae,PAPUA NEW GUINEAP. DtrLZf,LLFj.sherles Research, Department of Primary Industry, Kavieng,PAPUA NEW GUINEAB.L. KOJISL.I.H.S., Lae, PAPUA NEW GUINEAABSITACT

Surveys of coastal conlrtunities are lmportant in order to establish an inventory of thenationel resources. The use of an earth reaources satell-lte system (LANDSAT) is demonbtrated tocontain the spectral and spatial. resolution suitable for mapplng shallow water cofimunitles in troplcalPapua New Guinea.A Landsat multi-spectral image of the Kavieng region of New Ireland island in tt," BismarkArchipelago lras used to map shalloo water assernblages. As [Dst of the Paclfic is without narlti-spectralscanner images, we reconmend that a receiving station be established.

REST'IIELes dtudes des communaut6s littorales jouent un grand 16le dans 1 | 6tabllsselnent drunlnventaire des ressources nationales. Pour ce faire, il a it6 mont16 que lrutilisation dtun systlne desatellites (LANDSAT) pennettait de cartographier 1es communautds troplcales de Papouasd-e-Nouve1leGuin6e, en eeu peu profonde. Une lmage LANDSAT plurispectrale de la rdgion de Kavieng (NouvelleIrl,ande), dans I'archlpel Biemark, a ainsi servi i y cartographier des zonee peu profondes. Conme unernajorit6 du Pacifique nrest pas couvert per ltirnagerie acanner plurispectrale, nous reccr.rrnandons 1amise en place de postea r6cepteurs.


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INTRODUCTIONPapua Nect Grinea (ptlC) is a newly independentnation (1975) with a total land area of 46I,694sq km. IP consists of the eastern half of theisland of New Grinea and a myriad of srnallerislands and has a coastline of over 7,000 km'Ihe ocean within the Exclusive Fconomic Zone(EEZ) of apua New G:inea, which the governrentm.rst contrpl and regulate, forne a vast area overseven tifies the land ntass-To date large areas of PNG's seas are poorlycharted (Ygung, 1982; Done, 1983) and nrany coralreefs are only just being acknowledged in the

sc ientific literature (t


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atrDspheric scattering. Band 5 is FDre rapidlyattenuated by water and nost of it is lost in theupper 5 n. Band 6 contains a part of the red(visible) portion of the spectrum, but a majorityof its response is in the near infra-red. Inclear, deep water nDst near infra-red is absorbedwithin 20 cm of the surface. Band 7 penetratesonly the upper millineters of water, but isuseful in plotting heavily silted r,rater. In nostsituations band 7 is best used to disctiminateLand from water ntasses. These signals are, ofcourse, affected by the state of the sea and theatrosphere. It is recognized that LANDSAT candelineate, but not distinguish between thepatterns of bathynetry (e.g., Blna et al., 1978)and turbidity (e.g., Jetlov, 1976; ltunday andAlfoldi , 1979).Mapping spatial patterns and signaturevariations in deep water has been investigated inAustralia (Thom,son and Carpenter, 1981). ArDsand Alfoldi (L979) and ltunday and Alfoldi (1979)have conpared variations in the LANDSAT signaturewith actual physical nEasurerents of sedinentload in the r,rater colurm. Wolanski et aL .(1984) investlgated river plunns and mixing onthe !'raters of the ftlf of Papua and NorthernGreat Barrier Reef using LANDSAT irnagery.The selective absorption of light by water,nolecular scattering and incident radiation allplay a roLe in sea color. The color of turbidwater results from the selective absorption bysubstances carried in the nater (Jerlov, 1976).In areas where no co[ponent of the signal isconfused by sea bottom reflectance, properties ofseawater rny be studied using LANDSAT data.The use of LANDSAT on the Great Barrier Reefshelf has shown that vrhen the water is less than5 m deep, or turbid with concentrations higherthan 5 ppm of fine particles, bands 4 and 5 havesignificant signal leve1s above background noise(Jupp et al., 1983). In regions of deeper waterand/or less turbidity only snra11 variations inband 4 exist nraking it dtfficult to delineatedepth and water rnsses and thus requiringrepeated innges.Processlng Techniques

Computer aided analysis of LANDSAT data usesan interactive programrE cal1ed LANSAT runnlng ona PDP II 134 computer at the Papua New GuineaUniversity of Technology. The progran waswritten in f'ortren by Dr. Frank Honey to acceptdata from the Australian LANDSAT Station (ALS).The fornrat of the ALS LANDSAT tapes ls bandinterleaved by line (BIL),The data from the LANDSAT tapes istransferred to an RK-05 disc, where allocatedspace allows sub-scenes of 5IZ lines by 5I2pixels to be accomnodated. A BASIC programcalled LSSTOR is used to copy the data frorn thetapes to the disc from where the infornration isread off for LANSAT. Each LANDSAT image wasenhenced using an algorlthm devised by obtainingspectral signatures frorn several areas withsuspected siniler physical and biologicalfeatures.To display the LANDSAT data an Electohonecolor display terninal, a Matrox colour displayinterface was used. Up to 256 lines by 256pixels may be displayed ln I0 colors.A LANDSAT nultl-spectral illlage frorn acomputer corpatible tape imaged by Landsat 3 onl0 August 1981 (path 101, row 62) was used to

chart shallow water comnunities around KavlengHarbour (2034's., 150047,E.). A record of eachimage was nrade using a 200 mm lens on a 35 mmcartera and photographing the cathode ray screen.Shutter speeds of < 1/15 sec. $/ere used toellminate a band effect associated with thecathode ray tube projection.RESULTS AND DISCUSSION

The ImageUsing 10 color bands the habitats aroundKavieng are displayed in Figure I {nd codeslisted in Table 2. As this scene is just on thehorizon of the Australian Landsat receivingstation, there is a lot of noise associated withthis inage that is uncharacteristic of rrDstinngery. Owing to the relatively unsophisticateddata processing facilities available, we areunable to rrsnDoth'r the innge. Many of the singlecolored pixels sorE distance away from others ofthe sane color r.rould otherwise be eliminated asthey are noise artifacts and not the results oftrue sensing.Raw i,ANDSAT inragery of shallow water habltatssuch as coral reefs nny be difficult to interpretvisually. A dark patch may be interpreted as adeep lagoon or sea grass bed or nud flat and avery bright area could be a shallow lagoon withwhite sand botton or coral rubble. Wakes aroundislands can be delinated (Wol-anski et a1., 1984)any may be confused r+ith turbid or shallow water.It is therefore necessary that classifications beconducted with the aid of soneone knowledgeableabout the area and post processing surveys beconducted to sarple locations to verifyclassifications at least in the initial stages.The relative area and surface configurationof each color zone depends on the tidal levelduring inagery acquisition. A temporal

comparlson of the band zones of the sarr shallowv/ater habitat should indicate wtrich areas aresubject to the greatest spectral changes duringtidal npvenent.Sources of Error

There are two najor sources of error lnnrapping shallow water habitats uslng digitalclassification techniques. The first is incorrectly classifying a plxel aa a particularhabitat, e.g., coral, and the second is in theaccuracy of rrepping shallow water habitats whereerrors will occur from both classlficetion errorsand mlxed pixels on the field boundary.The accuracy of classifying the habltatsdepends upon a number of factors: 1) The abltityto discriminate the habitats from other habitateon the dates of acquisition. Submrged reefslook like rd.ldly turbld water and shallow reefelike rore turbid water. 2) The training dataused to establish class paranEtere for theclassifier m.rst be representatlve of that class.The best way of ensuring thls ls to statisticallysanple enough identical habitats. 3) Setting ofthe class decision values. If the decisionbounds are eet too tightly then reny pixels thatrepresent the c1ass, but having slightlydifferent responee values will not be includedand becom errors of onlssion. If the bounds areset too wide then there will be signiflcanterrors of commission.


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rror n es rna ng e areas o ehabitats are due to misclassification ofindividuall pixels as well as: 4) Errors in thenorninal piLxal size. The inage was not rectifiedto ground control hence minor variations in thealtitude df the satellite would result in adeviation from the 79 m X 58 m standard. 5)Mixed picture elerEnts on field boundaries. Ifthe percentage of the area of the habitats in themixed bouridary pixels was a uniform distributionand the Jlass decision values were properly set,then there would be negligible errors from thissource. However, as the habitats beconre snalletthe distr{bution of the percentage of eachhabitat in the mixed picture elements can beexpected {o diverge from a uniform distributionwlth an {ttendent higher probability that errorswill occui.

T can be used to provide reconnaissanceabling effective planning andof shalLow water habitats. Satellitesing does not replace the rlDreal nethods of shallow water nrapping,e the tine and costs associated withpplying supplenentary data, or data forassessrent. This particularly applies

o re e, sparse y areas avefer,r trained technicians like Papua New Guinea.Additionally, where data is required periodicallyover sofle considerabLe tine the costs ofconventional nethods would be prohibitive.The lirnitation to the application of LANDSATdata exists where there is inappropriate datahandling technology and expertise. In the caseof LANDSAT there is no requirenent for adaptionof satellite technology to 1oca1 conditions asthere is no involvenent with the sensingequipnent or its operations. Involvenent isconfined to the data produced from the satellitesensing and this can be acquired in a useablestate in readiness fot interpretation ornnnipulation. The two nain labor intensiveactivities are in the rnanipulation andinterpretation of the masses of data and in theproduction of naps charts or statistical datapresentations.Finally, the rDst imnediate limitation topotential users in the South Pacific region isthat there is no local receiving station in theregion. Hence, signals for less than 1/4 of thewaters in Papua New Guinears EEZ are currentlybeing received and there is no current data fromLANDSAT being received over any other area of theSouth Pacific.

Table 2: Interpretation of Figure 1Black and itrhite photograph of colorLANDSAT innge.Code t{ab itat Depth

Li ml tatiorisnBppingranageIlenrerDte seconventiobut can rthem by scontinuou

12345

Deep waterDeep shoalDeep coralDeep coral and sandMediurn depth coraland sandSandShallow sand andcoralSea grass beds

6

9 Mangrove vegetation10 Land or clouds


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CONCLUSIONDeveloping countries do not generally have asatisfactory enough inventory of their shallowwater habitats to develop and renage themeffectively. General rnapping activities,especially within the newly established EEZ, willrernain in an unsatisfactory situation for these

countries unless priorities alter, specialoverseas assistance is sought or new alternativetechnologies are employed.We believe that satellite based rerctesensing equiprFnt such as LANDSAT mrlti-spectralscanners can make a significant contribution tolow cost, synoptic, shallow water resourceassessnent prograns in developing countries withlarge exclusive economic zones.The nore sophisticated technology found inthe thenratic nepper in LANDSAT with its narrowerband widths and srnaller spatial resolution (30 m)will further increase the appropriateness ofsatellite based renr:te sensing technology for usethe napping the shallow water resources of thedeveloping countries of the Pacific.The anticipated launch of SPOT by the CentreNational d'Etudes Spatiales, France, in November1985 will provide an increase in spatial andtemporal resolution over LANDSAT imgery andshould be evaluated for use in the South Pacific.RECOMMENDATION

We recomrnend: I ) that two SPOT inngereceiving stations be established in the SouthPacific, 2) that these stations be placed in theregion of Tahiti and New Caledonia, and 3) thatSPOT products be freely available at reasonablerates to all nations of the South Pacific.Considering France's use of its PacificcoloniaL territories as an experinental groundfor its nucLear program and the concern thisaroused with respect to nuclear contamination inthe South Pacific, we feel it appropriate thatthe establishnent costs for the receivingstations be borne entirely by the Frenchgovernrent.

ACKNOWLEDGEMENTSWe would like to acknowledge the use of theLANDSAT facilities of the Departrent of Surveyand Land Studies and the corputer facilities ofthe Papua Ner,r Guinea Univetsity of Technology.Ifu. B. Nichols is particularly acknowledged forhis assistance in naintaining the corrPutingin fr as truc tur e .The Departnrent of Prinrary Industry, FisheriesResearch is gratefully acknowledged for theirfinancial support.

REFERENCESAMOS, C.L. and ALFOLDI, T.T. 1979. The determin-ation of suspended sedinent concentration ina macrotidal system using LANDSAT data.J. Sedinentary Petrology 49 :I59-I74.BINA, R.T., K. CARPENTER, W. ZACHER, R. JARA andJ.B. LIM. 1978. Coral reef napping usingLANDSAT data: follow up studies,

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International Syr|posium onof Environnent, ERIM, Annvol.3, pp. 2051-20f9.DONE, P. 1983. The preseflt status of hydrographyin Papua New Guinea. Internatio4al Hydro-graphic Review, Monaco 60:7-18.

S.W. HEGGEN and S.W. KENDALL. 19E1. Renotesensing by LANDSAT as support for qanageuentof the Great Barrier Reef. Proc$edings of2nd Australian Renote Sensing Conference,Canberra, P. Laut (ed.),9.5.1-9.5,1 6.JUPP, D.L.B., K.K. MAYO, S. KENDALL and S-HEGGEN. 1983. The use of LANDSAT data toassess bathynetry and topographic structurein the Great Barrier Reef region. CSIRODivision of Water and Land Resources.Technical Menorandum, P.60.KOJIS, B.L. and N.J. QUINN. 1984. Seasonal anddepth variation in fecundity of Acroporapalifera at two reefs in Papua New Guinea.Coral Reefs 3:765-172.KOJIS, B.L. and N.J. QUINN. 1985- Coral Reefs ofNortheast New Guinea. 5th InternatiQnal CoralReef Syrnposium, Tahiti.MOORE, G.K. 1980. Satellite renDte sensing ofwater turbidity. Hydrological Sciences,Bu11. Sci. Hydrolog.ffiMUNDAY, J.C. and ALFOLDI, T.T. 1979.of diffuse reflectance nodelssuspended solids nsasurerrent.Environnent 8 : 169-183.

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New Grinea Ilnlversity of Technology, p.99.YOUNG, F.R. 1981. Hydrographic charting bylite sensing: approprlate technologyPapua New Gulnea. the Journal of the neaYOlrNG, F.R. 1982. Charting Papua New culnearsweters - the hydrographer'e challenge. TheHydrographic Journal, U.K. 24:23-27.YOIING, F.R. 1983a. The hyregraphic - a translentalternative. The llydrographic Journal, U.K.27 zL5-L9.

eate 1-forAssoc-

theRIGHT, c.vegetaSurvey

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iation of Sur

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