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Extracting Parcel Boundaries from Satellite Imagery
for a Land Information System
Zahir Ali
ManagerPakistan Space and Upper Atmosphere Research
Commission (SUPARCO), PO Box 8402
Karachi, [email protected]
Shafiq Ahmed
Director General
Pakistan Space and Upper Atmosphere Research
Commission (SUPARCO), PO Box 8402
Karachi, Pakistan
Abstract Land Information System (LIS) primarily depends on
the availability of reliable spatial and non-spatial datasets.
Currently, the cadastral maps in Pakistan are mainly in paper
format lacking cartographic standards. Therefore, these maps
cannot be used directly as an input to the LIS. Such a situation
demands that all cadastral information in these traditional maps
be timely maintained in standard forms with quality indicators asinformation for the users. Considering the present situation in
Pakistan, this paper firstly elaborates the present cadastral
mapping system and the methods used for producing, updating,
and maintaining these cadastral data. This research paper
investigates on the use of satellite imagery in timely maintaining
of parcels boundaries and cadastral mapping in LIS. The abilities
of remote sensing imageries in parcel boundaries extraction and
cadastral mapping are assessed using QuickBird high-resolution
satellite images for two case study areas in the Khyber
Pakhtunkhwa province of Pakistan. This study introduces the use
of QuickBird panchromatic and colour imageries to develop a
method for cadastral surveying through on-screen digitisation
techniques. This study shows that the cost and time can be
reduced to its half if the cadastral maps are generated using the
newly developed technique.
Keywords- Cadastral Mapping, LIS, Image Processing, QuickBird,
Satellite Imagery
I. INTRODUCTIONUpdating land related information is very important so that
changes of ownership and division of property can be recordedin a timely fashioned manner for documentation. The use ofremote sensing (RS) images can play an important role forupdating and extracting land related information. Oneadvantage of using RS images is that they provide a historicalrecord of the areas that can be revisited in the future to see
what changes have taken place. In this way old images canprovide valuable evidence where conflicts occur in parcelboundaries [1]. Furthermore, traditional land surveyingapproaches are time consuming and require lot of efforts.Sometimes it is very difficult to do cadastral survey in remoteareas especially in mountainous areas when the weather is veryharsh. In this case RS images can be used as an alternative totraditional land surveying approach for spatial data acquisitionwhere most measurements can be done in the office [2].
Due to rapid development in the space born technologynowadays it is possible to generate thematic maps on various
scales keeping in mind end users requirements. The locationalaccuracy of maps is utmost important for certain applicationslike cadastral survey, infrastructure/utility maps, urban landuse, land planning and land consolidation works etc. Cay et al.[3] showed that using one-meter resolution imagery and GPScontrols, it is possible to achieve an accuracy of +/- 2 meters.
Recent advances in space-based data capturing techniques(imaging) have revolutionized the field of cadastral surveyingand mapping. All these improvements in satellite imaging haveled to availability of better quality data/pictures for mappingapplications [4]. Mamoru et al. [5] considered the possibility ofIKONOS imagery for making topo-cadastral maps and theirresults suggested that IKONOS imagery has advantageouscharacteristics of interpretation for making and updatingmiddle-scale topographical maps such as 1:25,000 comparedwith analogue aerial photo. They showed that horizontalaccuracy of IKONOS ortho-imagery varies between 1.0-1.2min flat areas and is worse in mountainous areas.
Land Information System (LIS) primarily depends upon the
available spatial and non-spatial datasets. In case of Pakistan,the available cadastral maps with land administration authoritydo not comply with the barest minimum standards for beingused directly as an input to LIS [6]. Such a situation demandsthat all these traditional maps to be updated and revised to astandard format in which the existing maps can serve as inputin the process of updating or revision.
Keeping in mind the importance of RS imagery, this studyincludes an assessment of QuickBird RS imagery as an input toland information system (LIS). This study focuses on theusefulness of RS imagery for parcel boundary surveying anddelineation to improve quality of existing cadastral maps withland administration agency. This study also highlights the
usefulness of RS imagery in cost & time estimation forcadastral surveying and mapping. The potential use of GarmineTrex GPS navigation receiver and ortho-rectified coloured
pan-sharpened QuickBird RS imagery having 0.6m resolutionis assessed in this study for extracting parcel boundaries.
II. METHODOLOGY, STUDY AREA AND DATA USEDA. Methodology
The workflow to be used in this research work forextracting parcel boundaries from RS imagery is shown inFigure 1.
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Figure 1. Workflow for extracting parcel boundaries from RS imagery
B. Study Area and Data UsedTwo study areas namely Zormandi and Shalmani in
Peshawar and Swabi districts were selected for this study toextract parcel boundaries from RS imagery. These two areaswere selected due to their distinct geographical features as theZormandi is a flat terrain while the Shalmani is a mountainousterrain. Location of these areas on the provincial map is shownin Figures 2. Zormandi is a flat and plain area with some urbanareas where some part of the area is built-up and very denseand frequent distribution of parcels is available. Shalmani is amountainous rural area where most of the area is open andmostly covered with some forest. The parcel distribution is
infrequent and not very dense.
Figure 2. Location of study areas
QuickBird panchromatic images of 0.6m and colouredimages of 2.4m resolution were acquired for both study areas.A SPOT5 stereopair with 2.5m resolution was also acquired forthe Shalmani area to extract digital elevation model (DEM)information. The DEM was used in ortho-rectification of theShalmani area. Due to flat nature of the Zormandi area, noDEM was used.
Two types of data were integrated in this study; namely theQuickBird ortho-images and field data including groundcontrol points (GCPs). Pre-processing techniques were carriedout with QuickBird ortho-images to assess usefulness ofremote sensing data for extracting parcel boundaries. Fieldvisits were carried out in consultation with BOR officials andland owners to locate and draw cadastral boundaries using fielddata and photogrammetric techniques. Ground surveys were
also carried out for collecting GCPs using hand held GPS(Garmin eTrex navigation receiver) for ortho-rectifying thesehigh-resolution satellite images.
III. EXTRACTING PARCEL BOUNDARIESThe parcel boundaries in flat area were easily identified on
enhanced ortho-rectified RS imagery. In this case, the parcelboundaries were trees, open area or presence of vegetation,roads or foot paths and water drainage with the presence of lowheight vegetation. The boundaries were digitized on ortho-rectified RS imagery through consultation with Patwari (landagency personal for keeping and preparing land records) andland owners in the field. In this case, field visits were carriedout along with map prints of RS imagery and land owners wereasked to find out their parcels boundary. The parcel
boundaries were then digitized using on-screen digitizingtechniques through laptop after confirmation from the landowners and Patwari in their presence. These parcel boundarieswere digitized through ArcGIS v9.3 software. The parcel
boundaries drawn in the flat area are shown in Figure 3.
Figure 3. Digitised parcel boundaries in flat area
Due to flat nature of the study area, it was not so difficult toidentify respective cadastral boundaries on RS imagery.Moreover, the existence of trees on parcel boundaries also
helped to identify parcel boundaries easily and the field sizeswere also according to the resolution of acquired imagery.
Similarly, the parcel boundaries in Shalmani area wereextracted from ortho-rectified RS imagery with the help ofPatwari and land owners in the field. In this case, field visitswere carried out along with map prints of RS imagery and landowners were asked to find out their parcels on imagery. The
parcel boundaries were then digitized using on-screendigitizing techniques through laptop in the field and wereconfirmed from land owners and Patwari in their presence. The
parcel boundaries were digitized using ArcGIS v9.3 software.
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The parcel boundaries extracted in the hilly area are shown inFigure 4.
Figure 4. Digitised parcel boundaries in hilly area
This area was mountainous in nature and it was not so easyto identify parcel boundaries on RS imagery. The field shapeswere not regular and field sizes were very small to identify on
RS imagery easily. Moreover, the RS data quality was not sogood due to mountainous terrain and irregular scattering thataffect quality of the data during acquisition. The shadow effectwas also observed on imagery in some parts of the study areacreating problem in identifying boundaries efficiently.
IV. CONCLUSIONSThis study introduces the use of QuickBird panchromatic
/colour imageries and Garmin eTrex GPS navigation receiverto develop a method for cadastral surveying through on-screendigitization techniques in the field. In this study, the QuickBirdimagery and GPS navigation receiver were used for extracting
parcel boundaries in consultation with the stakeholdersincluding land owners and land administration authorities. Inthis study, the Garmin eTrex GPS navigation receiver was usedfor collecting ground control points and SPOT5 stereopair wasused for generating DEM which were then used in the processof ortho-rectification. Using RS imagery, more parcels can besurveyed in a less time as compared to the old fashioned parcel
boundaries delineation method.
ACKNOWLEDGMENT
We acknowledge Mr. Nouman Shah Jadoon (MBR), Mr.Kifayatullah Khan (DLR), Mr. Ajmal Bhatti (SO) of the Boardof Revenue for their guidance and assistance with datacollection. We also thank Pakistan Space & Upper AtmosphereResearch Commission (SUPARCO), International Institute forGeo-Information Science and Earth Observation (ITC), the
Netherlands, Higher Education Commission (HEC) of Pakistan
and the Netherlands Organization for International Cooperationin Higher Education (NUFFIC) for providing this researchopportunity and funding assistance.
REFERENCES
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