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APPLICATION OF GEOGRAPHIC INFORMATION SYSTEM GIS)AND REMOTE SENSING TO LAND ASSESSMENT IN THE PHILIPPINES

Ju l ius P. MalingChief Remote Sensing TechnologistNational Mapping and Resource Information Authori ty NAMRIA)For t Bonifacio, Makati , Metro Manila, Phi l ippinesISPRS Commission IV

Abst rac t :GIS and remote sens ing are cur ren t ly being u t i l i zed in the Phil ippines for assess ingvar ious land concerns such as s o i l eros ion , upland u t i l i za t i on and proper ty values . Thesei s sues are pr io r i t i e s of the Government because they deal with the s ingle most importantnat ional resource , which i s land. Three 3) types of GISs are being used e .g . , ARC INFO,TYDAC SPANS and CRIES) in the overlay ana lys i s o f a t t r i b u t e maps, produced to a l a rgeextent using remote sensing techniques. The r esu l t ing decis ion maps are bas icconsidera t ions for the ef f ec t ive management o f s loping lands, and more impor tan t ly , forrevenue col lec t ion in prime agr i cu l tu ra l lands.Key Words: GIS/LIS, Remote Sensing Applicat ions, Land Applicat ions, Mapping.

1. INTRODUCTIONAbout 50 o f the h i l i p p i n e s ~ to ta l landarea of approximately 30 mill ion hec ta resi s arable . With a populat ion of 65mill ion, the pressure to open fores t landsto ag r icu l tu re , and to devise ways andmeans of ef f ec t ive ly u t i l i z i ng avai lableland resources i s expectedly great .There are three 3) main concerns involvingland in the country today: determiningaddi t ional areas for cul t ivat ion ,prevent ing fur ther degradat ion of landresources mainly through so i l erosion, andcol lec t ing the proper revenue from the

c i t i z e n ~ s use of the land. Such a widescope of in te res t necess i t a t es the use ofmodern evaluat ion methods, such as remotesens ing and GIS, which could give quickand accura te r e s u l t s .Prac t i ca l ly a l l of the a rable lowland areasare already under cu l t iva t ion , or aresubject to pr iva te r igh t s . As aconsequence, new s i t e s for agr icu l tu re mustcome from the uplands. This i s a verysens i t ive i s sue, s ince fo res t s andwatersheds must be protected for obviousecologica l and environmental reasons. Thedel ica te task o f determining upland areassu i ted to agr icul ture , t aking in to accountas many considera t ions as poss ible , can beeas i ly accomplished through the use of acomputer-based evaluat ion system, such asa GIS.The opening up o f s lop ing lands toagr icul ture , as wel l as other humanac t i v i t i e s in these areas such as logging,has the immediate consequence of increas ingso i l lo s s through eros ion. A secondarye f fec t of t h i s i s the accompanyings i l t a t i on and sedimentat ion of waterways,cont inuing onto coas ta l reef areas .Therefore , the same GIS must be able toaddress the need to map areas which aresuscept ib le to eros ion in various degrees.Final ly , as income i s derived fromsubjec t ing the land t o ag r i cu l tu ra l andother uses, proper assessment must be madefor taxat ion purposes. In many instancesin the country, t h i s e f f o r t i s hindered bythe absence of maps showing property

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boundaries .however, bemeans, whichin to a GIS.Provis ional lo t plans can,p lo t ted by photogrammetriccould then be incorpora ted

These photo-based maps can be the prac t ica lb a s i s for t ax assessment in many areas inthe country where cadas t r a l surveys havenot been undertaken. When more accura temaps or lo t plans become avai lable l a t e ron, the GIS database cons i s t ing ofd ig i t . ized photo-based maps could then beeas i ly revised or updated.This paper presents the techniques used bythe various pro jec t s of the GISAppl ica t ions Development Division o f theNational Mapping and Resource InformationAuthor i ty NAMRIA), the cent ra l mappingagency o f the Republic of the Phil ippines ,in applying GIS and remote sens ing fo r landassessment as s t a t ed above.

2. DESCRIPTION OF PROJECTS AND THEIRSTUDY AREAS

2 1 Determination of Sui tableAgricul tural Areas Upland

This project was in i t i a t ed in 1988 with thetown o f Tuba, in the province of Benguet,as the study area. Benguet has amountainous t e r ra in , and conta ins thehighes t peak in the i s l and o f Luzon, Mt.Pulag, whose elevat ion i s about 2,900meters above sea level . The province i sloca ted about 250 ki lometers nor th ofManila.The project aims to determine which areasin Tuba are su i ted to agr i cu l tu ra l usebased on such parameters as s lope , s o i ltype , a v a i l a b i l i t y of water , access ib i l i ty ,and ex i s t ing land use. ARC/INFO GIS wasused for t h i s purpose.

Soi l Erosion Suscept ib i l i ty MappingThe project a lso commenced in 1988, withthe Tamlang River Watershed, in the town o fBrooke s Point , i s land-province of Palawan,as the study area. Palawan i s a long,narrow i s land located about 300 ki lometerssouthwest of Manila, and i s one of the fewareas in the country where the environment

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i s still re la t ive ly undis turbed. For t h i sreason, grea t a t t en t ion i s devoted by theGovernment in conserving a l a w a n ~ s naturalresources .The purpose of the pro jec t i s to de l inea ted i f f e r en t areas in the watershed havingvarious degrees of suscep t ib i l i t y to s o i lerosion. The GIS which was u t i l i zed by thepro jec t for t h i s i s CRIES, which i s basedon the Universal Soi l Loss Equation (USLE).

Assessment of Agr icul tura l ResourcesThru Photo-Tax MappingIn i t i a ted in 1989 to a s s i s t loca lgovernments increase t h e i r revenue fromagr icul tura l l ands , t h i s pro jec t i s beingimplemented in three (3) towns: Pagudpud inI locos Norte province ; and Bulan andSorsogon, both in Sorsogon province. Thesetowns were chosen based on a number o fc r i t e r i a , foremost of which i s theava i lab i l i ty of new a e r i a l photography.Proper ty boundar ies are de l inea ted usingrec t i f i ed and enlarged ae r ia l photos asbase, and changes in declared ownership,land use and o ther improvements are noted.These data become the bases for revis ingand/or updating the tax assessments on theland. The r esu l t ing t ax maps and t axdec la r a t ions are then computerized usingTYD C SP NS GIS and Dbase 3+.Figure 1 shows the loca t ion of the s tudyareas for a l l the three (3) pro jec t smentioned above.

3. METHODOLOGYCol lec t ion o f Exis t ing Data

This i s done in order to gather the l ayersof data required for the GIS. Informationon topography, s lope , s o i l type, land use,hydrology and c l imate / r a in fa l l are commonlycol lected . Maps showing these are usua l lyava i lable from the appropr ia te governmentin s t i tu t ion .Once th i s s tep i s completed, the data gapscan be determined. Consequently, measurescan be adopted to ill in these gaps, suchas i n t e rp re t a t ion of ava i lable remotesensing data to ex t r ac t the needed ormissing informat ion .For example, land use information can bein te rp re ted from both aer i a l photos ands a t e l l i t e imageries. Dis tr ibut ion of so i ltypes can be accur a t e ly mapped from ae r ia lphotos when supported by adequate f i e ldsampling.

Preparat ion of Map Draf tsSince a GIS r equ i res both loca t ion anda t t r ibu te , it i s convenient and pract ica ltha t a l l inputs should be in the form ofmaps. For tuna te ly , 1:50,000 sca letopographic maps produced by N MRI areava i lable for a l l par t s of the country, andcan be used as car tographic base.Draf ts of the d i f fe ren t maps are preparedi n i t i a l l y , s ince these usua l ly wi l l have tobe updated and/or val idated in the f i e ld .

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The medium used i s t r ac ing f i lm, andb luepr in t s are made for f ie ld mappingFie ld Inves t iga t ion

Fie ld v i s i t s are made for severa l reasons .One i s to famil iar ize those involved withthe pro jec t with the biophysical condi t ionsof the area. Another i s to c o l l e c t datawhich may be required in the prepara t ion ofthe var ious thematic maps. For example, itmay be necessary to co l l ec t s o i l sampleswhich wi l l serve as ground t ru th data inthe prepara t ion of so i l maps.For t ax mapping purposes , extens ive f i e ldwork i s undertaken to ascer ta in proper tyboundaries. This r equ i r e s v isua l lyinspec t ing and loca t ing markers , a lsoca l l ed monuments, and mapping these ontoa e r i a l photographs.

Prepara t ion of Fina l Thematic MapsThe map dra f t s are revised or modifiedmanual ly using f ie ld observa t ions . Otherrequi red car tograph ic de ta i l s are f ina l izedsuch as legend, sca le , coordina tes , t i t l e s ,e tc . Colors are a l so added by hand.The f ina l maps are produced in s ing le copyonly , s ince the manual car tographic processi s t edious and pains taking.

GIS Data EntryData en t r y i s accomplished both by encodingand d ig i t i z ing map information, dependingon the GIS used. Map d ig i t i za t ion i scommonly prac t iced for both ARC/INFO andTYD C SPANS. On the other hand, dataencoding i s su f f i c i en t for the publ icdomain sof tware CRIES.I t i s worthwhile to note t ha t the datagenera ted by the three (3) systems arecompatib le in format.

Data AnalysisThere are three (3) bases for da ta analys iscorresponding to the three (3) appl icat ionareas : Sui tab i l i ty Cr i t e r i a , USLE, and theReal Proper ty Tax Adminis t ra t ion CodeRPTAC) o f the Phi l ippines .

The Sui tab i l i ty C r i t e r i a i s user - se t , andguides the c lass i f ica t ion o f an area intos u i t ab i l i t y types of high, medium and low.I t t akes in to account slope, s o i l depth,s o i l t ex tu re , drainage, and s o i l f e r t i l i t y .Other considera t ions a re ex is t ing land use ,access ib i l i ty and hydrology.The USLE i s pre - se t in to the CRIESsof tware . I t s var iab les are r a i n f a l l andrunof f , inheren t s o i l e r o d ib i l i t y , s lopel ength , s lope s teepness , land cover ands o i l conservat ion prac t ices .The RPT C provides ru les for tax assessmentof r ea l proper ty in the country. The taxdue i s a spec i f i c percentage of theassessed value, which i s the product o f theproper tyJ s area in hectares , market valueand assessment l eve l . The assessment l eve li s a cer t a in percentage which i s dependenton the nature o f the land use.

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117 118' 1 1 9 ~ 120 121' 122 123 124 I

IO aton Islands

~ r - - - - - - - - - - - + - - - - - - - - - - - ~ - - - - - - - - - - - - ~ - - - - - - - - - - - - + - - - - - - - - - - - ~ - - - - - - ~ - ~ n lLl N l If C H N N e L

~p a g U d P U ~ IIOCO Nort ~l I o } - - - - - - - - - - - - - ~ - - b r - - - - - - - - - - 4 _ - - + _ - - - - - - _ + - - + + - - - - - - - - - - - - - - ~ - - ~ - - - - - - - - ~ L - - - - - _ 4 - - - 1 1 8

----+----------------t------j----;IS

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---+--110

PalawanS U U se

(---+---1

Zambaanga

- -+- - - - -+- - -16

Figure 1 . Map of the Phi l ippines showing the three 3) p i lo t areasfor the land assessment s tud ie s us ing GIS and remote sensing.

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Generat ion of Decision MapsOnce the GIS has analyzed the data based onthe c r i t e r i a s t a t ed above, thecorresponding dec is ion maps can begenerated using a p lo t t e r o r pr in te r . Thedes ign of these outputs can be maded i rec t ly onto the computer, and thegenera ted maps are a l ready in t h e i r f ina lform.The procedure j u s t discussed follows veryc lose ly the opera t ions diagram of the GISAppl ica t ion Development Division of N MRIwhich i s shown in Figure 2.

4. DISCUSSION OF RESULTSSui t ab i l i t y Map of Tuba. Benguet

Figure 3 shows the S u i t a b i l i t y Map of thetown of Tuba in Benguet province. Three(3) c las ses of s u i t ab i l i t y to ag r icu l tu reare shown: high, moderate and low.Areas i den t i f i ed as highly su i tab legenera l ly have s lopes l e ss than 25 . Thesehave a t o t a l area of 1,255 hec ta res o rabout 3.50 o f the munic ipa l i ty . Areasi den t i f i ed as moderately su i t ab le genera l lyhave s lopes l e ss than 40 . These coverabout 2.349 hec ta res o r approximately 6.71of the town.Together , these two (2) s u i t ab i l i t y c las sesare charac te r ized by proximi ty to roads,and medium to low suscep t ' ib i l i ty to s o i leros ion/degrada t ion. The r e s t of the town,compris ing of about 31,428 hec ta res werec l a s s i f i e d as not su i ted to agr icu l tu remainly due to t h e i r s teep or very s teeps lopes .Sui tab i l i ty maps o f mountainous areas suchas Tuba are very important in themanagement of s loping lands in the countrys ince Phi l ippine law, in genera l , proh ib i t sthe use for agr icu l tu re of a reas havings lopes greater than 18 . However, i f thereare s t rong j u s t i f i c a t i o n s for rec las s i fy ingthese a reas , such as those presented bys u i t ab i l i t y maps, then they can bere leased o f f i c i a l l y to the recommendedland use.

Soi l Erosion Suscep t ib i l i t y Map ofthe Tam) ang Riyer Catchment inBrookeJs Point . PalawanFigure 4 shows the Soi l ErosionSuscep t ib i l i t y Map of the Tamlang RiverCatchment in the town of Brooke 's Point , inthe i s land of Palawan. Three (3) c las sesof s o i l erosion su sc e p t i b i l i t y are shown:s l ight , medium and high.The areas i den t i f i ed as highly suscept ib leto eros ion a re genera l ly open and denudeds teep fores t lands , with na tu ra l ly occurringlands l ides . The s o i l lo s s wi t h in theses i t e s are predic ted a t about 105 - 264 tonsper acre per year . About 269 hec ta res or2.3 of the catchment area f a l l under t h i scategory.Areas c l a s s i f i e d as media l ly suscept ib le toeros ion are a lso composed of s teepfores t lands , but are adequa te ly covered

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with na tu ra l vege ta t ion. The s o i l l os s int h i s ca tegory i s predic ted to be between 56- 96 tons per acre per year, encompassingabout 444 hectares o r 3.9 of the catchmentarea.The r e s t o f the basin i s predic ted to haves l i g h t eros ion of about 1 - 49 tons peracre per year . This i s t rue for 93.8 ofthe catchment or about 10,767 hectares .Soi l e ros ion i s a major environmentalconcern in the Phi l ipp ines , as th i scontr ibutes heavi ly to the degrada t ion ofthe prec ious agr i cu l tu ra l l ands . So i leros ion su sc e p t i b i l i t y maps providevaluable information t ha t can guide theestabl ishment of s o i l conservat ion measuresand other re la ted ac t i v i t i e s .4 3 Photo-based Tax Map o f San Is idro .Bulan. SorsogonFigure 5 shows the photo-based Tax Map ofa sect ion of the v i l l age of San I s id ro , inthe town o f Bulan, province of Sorsogon.The map presents information on proper tyi den t i f i ca t ion , boundaries and ownership.Figure 6, on the other hand. shows theproper ty index map (PIM) of the same s i t e .This map forms par t of the of f i c i a l recordsof the Municipal AssessorJ s Off ice o f thetown, and i s used as the bas is for t axassessment . Information on t h i s map i sbased on the cadas t r a l survey o f thev i l l age undertaken two (2) years pr io r tot h i s study.Comparing the two (2) maps r esu l ted to thefollowing observa t ions :a . there are maj o r changes in proper tyboundaries and corresponding lo tareas ;b. there are changes in ownership; andc . due to (a) and (b) above, revis ionsin t h e i r of f i c i a l land records andt ax assessments are necessa ry .Thus, for the purpose of r ea l proper ty t axva lua t ion, boundary maps based on rec t i f i edae r ia l photographs are indeed very usefulespec ia l ly in the absence o f updated landsurvey records. In ru ra l areas in thecountry , a systematic and accurate means ofmainta in ing land records i s v i t a l to theprevent ion of soc ia l unres t , s ince land i sthe s ingle most valuable proper ty o f thepeasant ry .

5. CONCLUSIONThe foregoing discuss ions have presentedonly the i n i t i a l s tud ies conducted by theGIS Applicat ions Development Divis ion ofN MRI in u t i l i z i ng GIS and remote sensingto address cur rent nat ional concerns inland assessment. Other pro jec t s dea l ingwith re levant i ssues in the environment andna tu ra l resources, such as f lood r i skassessment and the establ ishment of 3-dimensional resource information databasesare earmarked for implementation in 1993.For the current year 1992, N MRI cont inued

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I

1

OPERATIONS DIAGRAMGIS APPLICATION DEVELOPMENT DIVISION

NAMRIA

ENR CONCERN J ACTION PLAN 1SELECTION OF

PI LOT AREA

LAND USENAMRIA ;.

NATURAL DATA COMPLETEDENR - COLLECTIONRESOURCES DATAI socia - ECO-

~ R _ E _ A _ L _ W _ O _ R _ L D....I POLIT CA L D AT A t NCOMPLETE DATADIGITAL/MANUALINTERPRETATIONOF RS DATA

FIELD VERIFI -CATION / DA=rACOLLECTIONENRDATA

ENCODINGDIGITIZATION

CONVERSIONOVERLAYING

I----.".,I I STORAGEMODELLING EASUREMENTS

II

GENERATEOUTPUT

II : : : : ~ > .../ LI_R_E_PO_S_IT_O_R_Y_

GRAPHS

Figure 2 Diagram showing the s t andard opera t ing procedures of the GISppl icat ions Development Divis ion o f NAMRIA The methodology used in theland assessment s tud ie s fol lows t h i s diagram

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to implement the three 3) s tud ies j u s tdiscussed in d i f f e r en t areas in order tof ine tune the computer models used, andv a l i d a t e the i n i t i a l r esu l t s . I t i simpor tant to note t ha t NAMRIA hasconsciously exer ted e f fo r t s to involve theloca l government o f f i c i a l s and otherr e l evan t l oca l organ iza t ions in the conductof the s tud ies to ensure t ha t benef i t saccrue to the r es iden ts o f the s tudy areas .NAMRIA has a lso i n i t i a t e d s teps to t r ans fe rsome o f the technology to the l oca lgovernments.The Phi l ipp ines sha l l cont inue to u t i l i zemodern technology such as GIS and remotesensing in the protec t ion of theenvironment and the sus ta inable developmentof i t s . na tu r a l resources . These too l s havet ime and again proven t h e i r use f u l lne ss i nthese f i e l d s and the country have indeedmade gr ea t s t r i d e s considering i t s very1 imi t ed t e c h n i c a l and f inanc i a lc a p a b i l i t i e s .

References:Dive t t N G. and Pere t t P. A.,Int roduc t ion to GIS and i t s Applicat ion.Department o f Geographic Information.Woolloongabba, Queensland, Aus t r a l i a .Drisco l l R. S . Basa, V. F. and Cais ipM C., 1987. Forest land Evaluat ion forIntegra ted Land Use Planning, AProcedura l Manual for the Phi l ipp ines .Minis t ry of Natural Resources,Phi l ipp ines .Republ ic of the Phi l ippines 1974.Pres iden t ia l Decree No. 464 Enact ing aReal Property Tax Code. O f f i c i a l Gazet teManila, Phi l ipp ines Vol. 70, No. 26.Schul t ink G. e t . a l . 1987. User s Guideto the Comprehensive Resource Inventoryand Evaluat ion System GeographicInformation System. Michigan Sta t eUniversi ty/US Agency for In te rna t iona lDevelopment.Zachar, D., 1982. Soi l Erosion. Fores tResearch I n s t i t u t e . Elsevie r Scien t i f i cPubl i shing Company, Amsterdam-Oxford, NewYork.

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SUITABILITY MAPTUBA, BENGUET

LEGEND~ HIGHLY SUITABLEm ---- MODERATELY SUITABLEITlIlIl NOT SUITABLE

Figure 3. Su i t a b i l i t y Map of Tuba Benguetgenerated us ing the ARC/INFO GIS.

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. / i . .D0' - - - - -. Properly Boundary\( -, = -- Road'001 ---. Rivers

Figure 5. Photo-based Tax Map of San I s id rov i l l age in Bulan Sorsogon produced byde l inea t ing ac tua l proper ty boundar ies fromr e c t i f i e d black-and-whi te ae r ia l photos .

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SOIL EROSION SUSCEPTIBILITY MAPTAMLANG RIVER CATCHMENT

BROOKES POINT, PALAWANSCALE I: 140,000

TIillJLEGEND

SLIGHTMEDIUMHIGH

Figure 4. Soi l Erosion Suscept ib i l i ty Mapo f the Tamlang River Catchment r o o k e ~ sPoint Palawan generated us ing CRIES GIS.

N

BULAN, SORSOGONSCALE 1.16,000

LEGEND- - --. Property Boundary= . Road

. --- Rivers

Figure 6 . Property Index Map o f the samearea taken from the o f f i c i a l records of thetown s AssessorJ s Office . This map i sbased on convent iona l ground surveymethods.