"PIX' ILES 90" Nc>l.....néa - Tanlti. 19 - 24 rl.oV"EHnbre 1990

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REMOTE SENSING, GEOGRAPHIC INFORMATION SYSTEMS AND GLOBALPOSITIONING SYSTEMS. THEIR ROLE IN LAND USE/ENVIRONMENTALPLANNING AND MANAGEMENT IN THE SOUTH PACIFIC REGION

TELEDETECTION ET SYSTEMES D'INFORMATION GEOGRAPHIQUE LEURSROLES DANS L'UTILISATION ET LA GESTION DES SOLS ET DEL'ENVIRONNMENT DANS LA REGION DU PACIFIQUE SUD

N. ROLLINGS

RMIT Centre for Remote SensingVictoria university of TechnologyGPO Box 2476V, Melbourne, Victoria 3001 - AUSTRALIA

ABSTRACT

Countries of the Pacifie region are characterised by landmasses which are surrounded by vast areas of ocean. Thisunique geographical relationship creates management problemsthat are peculiar to the region. The isolated nature of theland areas means that conventional methods of data collectionsuch as aerial photography are not undertaken at regularintervals. Such repetitive coverage is necessary for efficientresource management practice. In addition, imaging in parts ofthe spectrum other than the visible is almost unknown.Remotely sensed data acquired from satellites is particularlysuited to this situation. Data derived from such systems canprovide repetitive, timely and accurate information about theearth and atmosphere at a variety of spatial and temporalresolutions. Data collection alone is not enough however. Suchdata need to be integrated and evaluated with other data setsso as to provide reliable decision making information. Inaddition, the regular coverage that satellite systems canprovide means that large volumes of data are produced and mustbe handled efficiently if maximum benefit is to be achieved.Geographie information systems provide the a~er to both ofthese situations. "1 9 rE~. b~o

ORsrOM Documentation O. R.S. T. O. M. Fonds Documentaire 501

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Integrating these two technologies, while providing highaccuracy ground control via global positioning systems gives apowerful resource management tool termed a GeographieInformation Processing System.

In conjuntion with Riedel and Byrne Consulting Ebgineers,the RMIT Centre for Remote Sensing has commenced a researchprogramme aimed at establishing a geographic database over theisland of Tongatapu, using a Geographie Information ProcessingSystem. SPOT multispectral and panchromatic data is being usedto augment existing data sets in the creation of the database.Once completed the database will be used to model a variety ofresource management scenarios.

The technologies used in this project are relativelyinexpensive. It should therefore be possible for thisprogramme to be extended and the countries involved to becomeresponsible for the compilation and maintenance of their owngeographic databases. One of the goals of this project istherefore to implement a methodology for technology.transfer.

RESUME

L'isolement et la vaste répartition géographique des paysdu Pacifique implique que les méthodes classiques de collected'information (par exemple, la photographie aérienne) sontcoûteuses et inappropriées. Ceci a fait que les levés aériensn'ont pas été acquis aussi fréquemment qu'il aurait éténécessaire pour contrôler les modifications de l'environnementet de l'utilisation des sols. Les données télédétectéesrecueillies par satellite sont particulièrement adaptées àcette situation. Lrot: peut avoir une couverture régulière à unprix raisonnable et une résolution spatiale adaptée. Cesinformations peuvent être analysées afin de produire desdonnées allant de la profondeur et de la qualité de l'eau àl'évaluation du couvert terrestre. La couverture régulièrefournie par les systèmes satellites implique que de grandesquantités d'informations sont produites et doivent être géréesefficacement si l'on souhaite en tirer le plus grand profit.Les systèmes d'Information Géographique peuvent servir devéhicule pour la gestion efficace de ces données.

Conjointement avec les Ingénieurs-Conseil Riedel et Byrne,le Centre de Télédétection RMIT a commencé un programme derecherche visant à établir une base de données géographiquessur l'île de Tongatapu en ayant recours aux technologies de latélédétection et des systèmes d'information géographique. L'ona utilisé les données multispectrales SPOT pour compléter lesséries d'informations déjà existantes, telles que le type decouverture et la bathymétrie côtière. Les informationsobtenues par ce procédé ont été introduites dans un PCArc/Info, un Système d'Information Géographique à basevecteur. Ce document explicite les résultats acquisjusqu'alors, et présente quelques applications de cette base

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de données dans le domaine du contrôle de l'environnement etde l'utilisation des sols.

Les technologies employées dans ce projet sontrelativement peu coûteuses. De ce fait, il devrait êtrepossible d'extrapoler ce programme et d'envisager que les paysconcernés se chargent de la compilation et de l'entretien deleurs propres bases de données géographiques en faisantl'acquisition du matériel informatique et des logicielsnécessaires. L'un des objectifs de ce projet consiste donc àmettre en oeuvre une méthodologie de transfert de technologieau moyen de laquelle les urbanistes et gestionnaires locaux dela région pourront être formés à la réalisation de leurspropres bases de données.

INTRODUCTION

The countries of the Pacifie region are characterised bysmall land areas with vast areas of ocean. Land is therefore aprecious resource and needs to be managed as efficiently aspossible to ensure continued and sustainable development.Considering that these small areas of land provide much of theregions exports, up-to-date information on infrastructure,productivity and condition is essential to the management ofland resources.

Of equal importance are the oceans which supply much ofthe food for the people of the Pacifie region. Trends ofdwilling seafood supplies and declines in water quality havebeen evident for sorne time, (Australian BroadcastingCommisssion, 1990).

Pacifie countries also face unique resource managementproblems due do the large distances between centres. Theselarge distances are one of the major obstacles to thedevelopment of the region, (Australian BroadcastingCommission, op.cit.). Increasing populations caused by anincrease in the growth rate and migration of people from outerislands to the major centres is also placing a strain on theresources of the region.

For these reasons it is important to map, monitor and planthe development of the regions terrestrial and marineresources.

Environmental and resource management decisions need to bebased on reliable and comprehensive information. The isolatedand widely spaced geographic distribution of the Pacifiecountries means that conventional methods of data collectionare expensive and infrequent.

Data acquired from Remote Sensing (RS) platforms canprovide repetitive, timely and accurate information about theearth and atmosphere at a variety of spatial and temporalresolutions (Table 1) . Data collection alone is not enough

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however. Such data needs to be integrated and evaluated withother data sets so as to provide reliable decision makinginformation.

Geographie Information Systems (GIS) provide a vehicle forthe efficient handling for the large amounts of spatialinformation produced by image analysis systems. A GIS is anautomated system designed to capture, store, retrieve, analyseand output aIl forms of geographically referenced data.

Once entered into a GIS, information can be modelled for avariety of purposes including land capability mapping, erosionmodelling and test scenarios for environmental impactassessment. An added bonus of using a GIS is that other formsof data can be managed such as facilities and cadastralinformation.

The integrated use of remote sensing and geographicalinformation systems is essential for efficient use of data.Each system can be used in isolation provide useful benefits.However, combined in their application they form a verypowerful tool for resource management and planning.

The use of the Golbal Positioning System (GPS) inconjunction with RS and GIS adds a dimension of spatialaccuracy to these data not possible or affordable using moretraditional surveying methods.

RELATIONSHIP BETWEEN REMOTE SENSING GEOGRAPHIC INFORMATIONSYSTEMS AND GLOBAL POSITIONING SYSTEMS

Remote sensing systems are primarily concerned with theacquisition of data which is then transformed into informationvia an image analysis system. GIS is primarily concerned withthe management, analysis and modelling of spatially relatedinformation such as that derived from an image processingsystem. The marriage of these two technologies is therefore alogical step in the evolution of a Geographie InformationProcessing System (GIPS ) , a system which handles aIl aspectsof data input and processing.

The current trend is for RS systems to provide data atincreasingly finer spatial resolutions. Consequently there isa requirement for an increase in the spatial accuracy in theground control used to rectify such data. To this end, theincorporation of GPS data to georeference both remotely sensedand GIS data is essential.

Figure 1 shows the relationship between RS, GIS and GPSas developed by the RMIT Centre for Remote Sensing,departement of Land Information at the Victoria University ofTechnology in Melbourne, Australia.

Remote sensing can benefit from ancillary data sets beingincorporated in the image analysis process. For example the

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classification accuracy of areas of mangrove could be improvedby incorporating digital elevation data. This thematic layercould then be entered into the GIS as a layer suitable forfurther analysis. This two way flow information is thefundamental principle which makes the merging of thesetechnologies so successful.

GPS can be used to provide accurate and selectable groundcontrol coordinates useful for the rectification of satelliteimagery. Ground control points can be measured to sub­centimetre accuracy if required. Word undertaken at the RMITCentre for Remote Sensing has shown a substantial increase inthe rectification accuracy of LANDSAT TM data when using GPScontrol instead of l: 25 000 map coordinates. Table 2 showssorne of the accuracy improvements achievable.

GPS is also useful for ground control of data input for aGIS. GPS can also be used to accurately locate featuresidentified by satellite imagery and GIS analysis when in thefield undertaking accuracy assessment.

Within the RMIT Centre for Remote Sensing the link betweenRS and GIS is provided through the ERDAS - ARC/INFO live linksystem. ERDAS is an image processing system and ARC/INFO is aGIS. The live link allows geographic referencing parameters tobe passed between the two software programmes. GPS input isvia TRIMBLE NAVIGATION 4 000 ST GPS receivers.

The integrated use of these three technologies is seen ascentral to the RMIT Centre for Remote Sensing in its mapping,monitoring and modelling programmes. The term GeographieInformation Processing System (GIPS) has been adopted for thisintegrated approach.

THE ROLE OF A GIPS IN RESOURCE MANAGEMENT

The definition of "resource" in this paper is very broadand encompasses the land, the sea, the people, the air and theenvironment.

The role of a GIPS in the management of resources is givenin figure 2.

If a resource is to be managed efficiently and effectivelythen a weIl defined management plan is required. Thismanagement plan is based on existing resources existinginfrastructure, current and predicted requirements of theresources as weIl as environmental and politicalconsiderations.

Insular environments such as those in the Pacifie regionoften lack the necessary surveys to adequately document thebio-physical resources of their terri tories. This problem is

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not restricted to the Pacifie region. Few if any of the socalled developed nations currently have adequate informationon their bio-physical resources from which they can make soundresource management decisions. To this end a GIPS is useful inacquiring and storing base line data on the bio-physicalresources and infrasturctures of an area.

Once base line data has been collected current resourcescan be analysed ans an appropriate management planimplemented.

Other data can then be collected and analysed with respectto the base line data set. For example, agriculturalstatistics could be compiled and compared to physicalparameters such as soil type, slope, aspect, hydrology and soon. Using these simple modelling techniques a land capabilitysurvey could be conducted to ascertain the optimum land usefor different land terrain units.

At this stage an evaluation and modification of themanagement plan might be appropriate.

Once established a geographic database, managed by a GIPScan be used to model and make recommendations on developmentapplications over an area. Such applications may be deemedacceptable, in which case the GIPS can be used to remap theresources after the development and to monitor the effects ofthat development. Potentially harmful projects would hopefullybe recognised before implementation and either be disallowedor returned to the applicant for modification so as to satisfythe requirements of the management plan.

CASE STUDY - GEOGRAPHIC DATABASE OVER THE ISLAND OF TONGATAPU

In order to demonstrate the application of a GIPS to theconstruction of a geographic database, the RMIT Centre forRemote Sensing, in conjunction wi th Riedel and ByrneConsulting Engineers, have undertaken a research project toconstruct a partial geographic database over the island ofTongatapu in the Kingdom of Tonga. Available data setsinclude :

1. 1973 1:25 000 topographie map over the island2. 1988 SPOT XS imagery3. 1990 SPOT Panchromatic imagery4. Limited Black and White aerial photography (recent colour

photography is now available)5. Sorne local knowledge.

Colour figs. P18A and P18B show satellite imagery over theisland.

In addition the following information would be desirablebut as yet is unavailable.

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1. Soils map2. Geology map3. Sorne batymetric data to calibrate satellite derived depths4. Population statistics5. Cadastral information6. GPS derived ground control over the island

The principal aim of the project is to demonstrate theusefulness of a GIPS to the management of the Kingdom ofTonga.

The technologies used in this project are relativelyinexpensive. It should therefore be possible to implement amethodology for technology transfer whereby local planners andmanagers of the region can be trained to implement their owndatabases given appropriate staff resources.

The database

The following layers have been entered into the GIS at ascale of 1:25 000.

1. Roads - Works has commenced on updating the road networkusing the high resolution satellite data (la m groundresolution)

2. Contours - DEM- Slope- Aspect

3. Estates4. Sorne facilities

Work currently underway includes

1. Bathymetrie mapping of the surrounding waters2. Water quality monitoring for Fanga'uta lagoon3. Mangrove mapping using satellite data supported by aerial

photography4. Raster scanning of aerial photography into digital format

for use in image analysis system5. Land cover mapping.

Colour figs. P18C and P18D show sorne of the data layersentered into the GIPS.

The project has been hampered by several factors.

1. Lack of adequate ground control for rectification ofsatelliteimagery

2. No external funding has been provided for the study3. Workers on the project have no ground truth information on

which to base their analysis.

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Nevertheless the proj ect has achieved sorne results andthese are presented here.

UPDATING OF ROAD NETWORK

The 1990 SPOT satellite imagery with a spatial resolutionof 10 metres was rectified using the 1:25 000 map. This imagewas only received a week ago.

The existing road network as digitised from thetopographie map was then overlayed on the imagery. New roadsnot shown on the map were clearly visible and could bedigi tised from the screen using the capabili ties of the GIPS(colour fig. P18E), note the new roads shown in purple). Whencompleted a new road map can be produced using thecartographie output capabilities of the GIPS. Accurate groundcontrol from GPS would allow more accurate road mapping totake place.

DERIVATION OF A DIGITAL ELEVATION MODEL

Once the contours were digitised into the system the GIPScan derive a digital elevation model (colour fig. P18F). Sucha model can be used to derive slope and aspect. It is alsousefuI to present information modelled in the GIS so that itcan be assimilated within a topographie context. Colour fig.P18G shows a DEM of the region around Nuku'alofa and Fanga'utalagoon. The coast and road network has been draped over thisDEM to demonstrate this principle. When completed the mangrovemapping results could be presented in a similar way. The DEMcan also be used to simulate sea level rises of variousmagnitudes and model the areas most under threat stormactivity and inundation. Once completed the GIPS can also beused to create a 3 dimensional map of the coastal bathymetry.

CONCLUSIONS

The integrated use of remote sensing, geographicinformation systems and global positioning systems into aGeographie Information Processing System provides resourcemanagers with a powerful tool to assist them in the efficientand effective execution of their duties.

This is particularly so in the Pacifie region wheregeographical consideration make it difficult to monitorexisting resources using more conventional approaches such asaerial photography.

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The unique problem faced by the Pacifie countries meansthat they have much to gain from the Implementation of thesetechnologies. More efficient management of existing resourcestaken within the context of current and future needs wouldmean easier, efficient and more rapid development.

The technologies used in this kind of project arerelatively inexpensive and it should be possible for thisprogramme to be extended such that Pacifie nations themselvescan create their own databases provided the appropriatepersonnel can be trained.

AKNOWLEDGEHENTS

The assistance of SPOT Image Services with respect to theacquisition of the SPOT panchromatic imagery is gratefullyacknowledged.

REFERENCES

AUSTRALIAN BROADCASTING COMMISSION, 1990. HorizonsAustralian Volunteers Abroad. Programme broadcast 26/10/90.

LEMAIRE O., L. LOUBERSAC, H. VARET, P.Y. BURBAN, F.CHENON, 1990. Bathymetrie modelling using SPOT data TheAitutaki example (Cook Islands). Proceedings of the FifthAustralasian Remote Sensing Conference, Perth, WesternAustralia, 8-12 Octobre.

O'RIORDAN T., 1977. Perspectives on Resource management.Monographs in Spatial and Environmental Systems Analysis, PionLtd. London.

SOPAC, 1989. Proceedings of the Eighteenth Session of theSouth Pacifie Applied Geoscience Commission, Canberra,Australia, 2-13 Octobre.

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Table l Source of remotely sensed dada suitable for urbanapplications.

LANDSAT THEMATIC MAPPER

FUTURE - 15 m PANCHROMATIC BAND - STEREO

- 30 m- 16 days

7 bands

SPOT

PANCHROMATIC

MULTISPECTRAL - 20 m- 2 to 26 days- 3 bands- stereo

- 10 m- 2 to 26 days- 1 band- stereo

FUTURE - 5 m PANCHROMATIC BAND

SOJUZKARTA - VARIETY OF SPACE PHOTOGRAPHY - eg MK 4- 6 m- 3 bands- stereo

Table 2 : Comparison of model accuracy between GPS derivedground control points and 1/25 000 map derived ground controlpoints.

MODEL ORDER ERROR X ERROR y

AFFINE GPS 0.399 0.386AFFINE MAP 0.535 0.525

QUADRATIC GPS 0.480 0.410QUADRATIC MAP 0.937 0.852

CUBIC GPS 0.980 1.180CUBIC MAP 3.608 3.107

GCP = GLOBAL POSITIONING SYSTEM DERIVED POINTSMAP = 1:25 000 DERIVED POINTS

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GISTop oqr u phy

Vegetation

Soils etc.

LOCATION OF

FEATURES

GROUND CONTROL

DATA INPUT

G UNDCO TROL

TR NINGAR S

GPS

!MArs. DECISION MAKING---------

Figure 1Informationdevelopement

Relationship between Remote Sensing GeographieSystems and Global Positioning Systems. Theof a Geographie Information Proeessing System.

~:@2~ GIPS AREA MANAGEMENT PLAN

RA'; T Centre for Ronvo to Sensing _

Figure 2 Role of a Geographie Information Proeessing Systemin Resouree Management.

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P18

P18A : SPOT multispectral Image of Tongatapu acquired June1988. C CNES 88/dist. SPOT IMAGE.

P18B : SPOT Panchromatic Image of Tongatapu acquired July1990. C CNES ~O/dist. SPOT IMAGE.

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Roads overPanchromaticImage. Roadsshown in purplehave been up­dated fromimagery.

PISD Roads and Airport.

PIS

PISC Contours.

PISE

Pl8

Pl8F : Digital Elevation Model of Tongatapu. View looking tothe North.

Pl8G : Digital Elevation Model of Nuku'Alofa and Fanga'utaLagoon. View is looking towards the South.

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"PIX'ILE 90"

Journées internationales tenues à Nouméa· Nouvelle-calédonieetà Tahiti· Polynésie Française

19/24 novembre 1990

International workshop held at Noumea • New caledoniaand Tahiti French· Polynesia

November19/241990

ilt:EAfER

© ORSTOM, Nouméa. 1992

Irnprimo par le Centre ORSl DMde Nouméa

Septembre 1992

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