Cadastral reform in Malaysia: A vision to the 2000s
Wan Aziz., Majid. K, Sahrum, S.
Department of Geomatic Engineering
Faculty of Engineering & Geoinformation Science
University Teknologi Malaysia,
81310 Skudai. Johor.Malaysia
Directorate of Surveying & Mapping,
Malaysia Kuala Lumpur, Malaysia
Cadastral surveying aims at defining and guaranteeing legal property boundaries, and determining coordinates of all measured points to give information on the size and nature of land use. The role of a land registration system like the cadastre is specifically regulated by laws and other administrative rules and guidelines for a uniform implementation of the system. It will not be possible to design a cadastral system suitable for any case and any circumstances, especially the socio-economic basic conditions are different from country to country. The different forms of land tenure and the legal situation in this field will give the framework for a cadastral systems and how to carry out its technical features. On the other hand, the political circumstances are dictating the financial and personnel investment in the cadastral system The cadastral system in Malaysia is a system that provide more secure basis for land and property ownership. It consists of the surveying and recording mechanism in describing the cadastral information, for example boundary line (in the forms of bearing and distance), location and area of a given parcel of land (lot). The demarcation and delineation of the boundaries are also part of a cadastral survey aimed at defining the parcels on the ground and securing evidence for the re-establishment of the boundary if the marks disappeared.
The typical surveying technique adopted for the cadastral survey which capable of bearing (direction) and distance measurements is the survey equipment called total station (digital theodolite & electronic distance measuring unit). However, the main drawback of this conventional technique is that it requires intervisibility between control points, and this has restricted the productivity of the surveyed lots. Several drawbacks as well as the great demand for efficient and effective cadastral management have prompted various surveying and mapping authorities in the world (including Department of Surveying & Mapping, Malaysia - DSMM) to study the concept of 'Coordinated-based Cadastral System - CCS', see Boey and Hill, (1995), Barnes, et.al. (1996), McDaid, et.al., (1997) and Wong, K.S., (1999). The CCS means that 'bearing and distance' are derived legally from the final adjusted coordinates. Realising the needs of integrating the cadastral data with other map based information (all forms of spatial information)for GIS applications, the CCS has to be prevailed in the near future. The emphasis of the CCS concept is the geocentric datum, a single projection system for the whole country and the application of least squares adjustment procedure in the distribution of survey errors. At present, DSMM have already implemented the cadastral system in digital environment: Computer Assisted Land Survey System (CALS), Cadastral Database Management System (CDMS), the Computerized Land Registration System (CLRS) and National Infrastructure for Land Information System (NaLIS). Therefore, by implementing the CCS, it will opening up and integrate the benefits from advances of technologies into reality.
Several performance tests have been shown that the GPS technology efficiently provides users precise positions. Nowadays, by using modern GPS techniques such as Rapid-Static, Stop & Go and Real Time Kinematics (RTK), many points can be observed in a relatively short period of time with good accuracy as those obtainable by conventional EDM/Total Station surveying. These can increase productivity, reduce cost and manpower, and at the same time is capable to challenge the cadastre task. Furthermore, for multipurpose cadastre surveys, GPS positioning is a desirable and adequate method for establishing and strengthening the national and regional geodetic networks. Therefore, a move to introduce multipurpose coordinate-based cadastre using GPS technology has been under way in Malaysia, in recent years. One of the main advantage in CCS is that it facilitates the use of rapid spatial data acquisition, storage, processing procedure and management techniques, even though several issues unique to the GPS technology need also be addressed. This paper is concerned with the feasibility for implementing a nationwide Coordinated Cadastral Surveying (CCS) in Malaysia. Here, the performance of the GPS technology under the controlled conditions of the cadastral system is tested.
Triangulation and GPS Networks
Employing GPS surveying requires well-established regional and global geodetic networks. They are essential for the preparation of consistent regional and global spatial data. In our case, the Malaysian Datum (West Malaysia), adopts the Modified Everest ellipsoid as a reference with its origin fixed at Kertau, Pahang. The first national geodetic network known as Malayan Revised Triangulation (MRT) consisted of 70 trigonometrical points which is geometrically connected by 340 observed angles and 2 geoidal distances. The MRT network serves as a main control for surveying and mapping activities in our country, including cadastral survey (e.g. standard cadastral traverses). Unfortunately, some of the triangulation points have been 'destroyed' and/or not well maintained. Thus, for the past 15 years, in conjuction with GPS campaign, the re-establishment and updating of the triangulation trig points have been greatly demanded in Malaysia. The Malaysian Datum is different from WGS84 that GPS employs as the reference frame. While the request for the coordinates referenced to the existing datum are still large, demands for the well-accepted global coordinate systems have been also growing. Therefore, a move to adopt geocentric datum has been underway in various country, including Malaysia because it can provide unified geographical reference frame, Teng, (2001).
In Malaysia, serious precise surveying by GPS has started with the establishment the national 1st. order GPS network in 1992, providing a consistence set of coordinates in WGS84. The network is consists of 238 GPS stations (and 171 stations in East Malaysia) which formed the backbone of the National GPS Network. Since then, GPS surveying has been practiced for various surveying and mapping activities in the country. Current trend indicates that for the most precise, effective, economical and fast applications, some form of permanent GPS network should be established. In order to realize such requirements, DSMM has started establishing permanent GPS tracking stations or Malaysian Active Satellite System (MASS) at the end of 1998. Currently, MASS network is consists of 17 permanent GPS stations over the country for scientific research purposes, (e.g. crustal movement, unified datum, earth rotation parameters, atmospheric studies, etc. This network is known as the Zero Order Geodetic Network and it complies with international standards to provide the highest precision for positioning in Malaysia. The National 1st Order GPS Network has been successfully connected to MASS network and its coordinates referred to the ITRF2000 Epoch 00.0 with an accuracy of 1 to 3 cm. Thus, it will form the backbone for the national adjustment of the existing GPS stations to defined all coordinates in ITRF system. By doing this, the adoption of geocentric datum will definitely lead to a homogeneous national coordinate datum across the country (including East Malaysia). Subsequently, in order to benefit directly from proposed geocentric datum, a new projection (and associated parameters) has to be developed so as to allow the coordinates to be projected directly from control network snd dstum to the plane grid system. However, the new projection should have the characteristics of conformal and also, at the sane time maintaining minimal scale distortion.
Coordinate system and transformation
The national (local) geodetic coordinate system consists, in principle ellipsoidal coordinates at a defined set of points. In practice, the Kertau Datum of the MRT, is defined in terms of only the horizontal components (f, l) of the Modified Everest Ellipsoidal coordinates: there is no explicit definition of the ellipsoidal height, h. Now, the first and fundamental answer that any GPS users requires is the question where am I on the Malaysian topographic map at scale 1:50,000?". The GPS receiver will yield geocentric coordinate system in the reference frame to which the satellite orbits are referred. It will not produce coordinates in the local mapping system. If geocentric GPS coordinates are to be very useful for local system, there has to be a coordinate transformation process (function, algorithms) whose form will depend on local information about the mapping control system and the shape of the geoid. In our case, datum transformation enables us to combine GPS measurements with the existing conventional terrestrial measurements whereby 32 triangulation points (MRT system) are used to determine 6 transformation parameters between MRT and WGS84 system. The parameters are estimated by least squares methods using model Bursa-Wolf transformation model - see Table: 1.
The existing coordinate systems used for mapping and cadastral survey in West Malaysia is the conformal Rectified Skew Orthomorphic system (RSO) and Cassini Soldner system (CS), respectively. The RSO projection system is also based on the Modified Everest reference ellipsoid while the Cassini Soldner is a plane coordinate system for local cadastral system. The mathematical projection models and associated coefficients for RSO and Cassini coordinate systems can be found in Hotine (1947) and in Richardus and Alber, (1974), respectively. A number of origins have been adopted when establishing local Cassini coordinate system, resulting in each state in West Malaysia using a difference origin.. Since the adjusted GPS coordinates are in geocentric datum, i.e. WGS84, they are need to be transformed into these established local systems. The transformation procedure from global datum to local datum (mapping and cadastral system) involves a lengthy computation steps as followed:
GPS-based cadastral survey
Nowadays, the precision GPS receivers can provide coordinates which are sufficiently accurate for cadastral purposes in rural areas. More importantly, these receivers offer an opportunity to significantly lower the cost and time typically required for cadastral surveys. But, the most fundamental aspects that have to be considered in this study is 'the GPS practice for the use of GPS in cadastral surveying so that is similar to those that already exist for EDM/total station procedures. This will provide means of ensuring the highest quality practices are adhered to which surveys pertaining to land boundaries and title. Therefore, in designing and testing a GPS methodology for cadastral surveying, the following criteria should be adopted, Barne, et.al. (1996).
The SKI adjustment was performed after the completion of GPS data entry (i.e. after download). For the total station traversing, the input data are in terms of bearings and distances (as in the CASE (i)) using a written Fortran program. The output is in the form of adjusted observations, coordinates and information for statistical analysis. For both cases, a set of adjusted coordinates are compared with their corresponding values, i.e. Total Station Values for CASE (i) and CP values for CASE (ii). The comparison between the two sets of coordinates are sumnmarised in Table: 3 and Table: 4, respectively. Figure: 1 illustrates the differences in distance and bearing between GPS derived-values and the corresponding values of conventional traverse, i,.e. CASE (i), while Figure: 2 depicts the similar output for CASE (ii).
Computed area for GPS Survey = 44323.82 m2
Computed area for Conventional method = 44335.67 m2
Difference = 11.85 m2
Figure: 1 The differences in distance and bearing for CASE (i)
From Table: 3 and Figure:1, it is apparent that the average difference in distance between the GPS cadastral survey and conventional cadastral survey is less than 3 mm. The minimum and maximum differences in distance is occured at traverse legs S3-S4 and P5-P7, respectively. The linear misclosure is also being computed for the corresponding line. All traverse legs have shown that they are fulfilled the 1st order (class) of the cadastral survey requirement with the exception of traverse legs S1 - S2 and P5 - P7. In our country, we adopted the ratio of better than 1: 8000 as a 1st. class cadastral survey. However, the linear miclosure for the traverse leg S1 - S2 is still within the range of 2nd. Class requirement for cadastral survey (i.e. better than.1: 4000). The traverse leg P5 - P7 shows the lowest accuracy in terms of linear misclosure. This may due to the GPS observational factors (biases) such as multipath, the antenna centering error, atmospheric effect, etc. Similarly, it can be seen that the minimum and maximum values of bearing differences between the GPS survey and the total station methods is -8" and 42", respectively. In general, the results show that for shorter traverse legs, the differences in bearing is quite significant. Furthermore, one may also noticed that the differences in distance and bearing between these two techniques is not consistence due to some biases in GPS observations (e.g. setting errors, multipath), conventional survey values (e.g. Bowditch adjustment) or in the coordinate transformation processes (e.g. coefficients). The area for the test site is also being computed for both the GPS and conventional surveys. The result has shown that there is no significant difference in computed area between areas computed from the GPS coordinates and the conventional traverse (i.e. 0.12%). Therefore, it is believed that the differences of less than 1% could be achieved for lot area of less than 5 hectares.
Figure 2 . The differences in distance and bearing for CASE (ij)
From Table: 4 and Figure: 2, it is seen that the difference in distance is less than 2cm, having a minimum and maximum value of 0mm and 18mm for traverse leg M6-M11 and M8-M9, respectively. The overall results show that longer distance between stations (in conventional cadastral traverse) produced a significant distance errors. On the other hand, it seems that the magnitude of errors in bearing (angular measurements) could be large for a shorter distance, see traverse legs M10-M11, M11-M12 and M13-M14. This is due to the fact that for a shorter distance, the pointing errors is quite large compare to longer distance. Also, one may noticed that the differences in distance and bearing between the GPS values and CP values is not consistence thoroughout the traverse legs. Agains, some errors may occured in GPS observations, for example multipath, observational noise, setting errors, and/or errors in coordinate transformation processes (e.g. coefficients), errors in conventional traverse surveys, e.g. theodolite setting/pointing errors, Bowditch adjustment, etc. The size of area for the test site is also being computed for both GPS and conventional surveys, see Table: 5. This table indiactes that in general differences of less than 1 meter squares could be achieved for lot area of less than 1 hectare.
The results from this test shows the potential of using GPS (rapid static) in cadastral survey in Malaysia. But, it has to be recognised that in order to use GPS technology for cadastral surveys, GPS measurements must be legally traceable, i.e. calibration procedures, GPS field control survey and office procedures. Apart from this, several aspects should be taken into account for the conception, and this may include the underlying features of a coordinated cadastre as indicated by DSMM and the future direction of the cadastre.
The technical design of a cadastral system in a developing country likes Malaysia needs a precise definition of the requirements and aims at such a system. A cadastral system is not a monolithic block. It should be designed to fulfil the changing legal demands and demands of administration and the private sector. Appropriately, it should be able to develop it into a great variety of multipurpose (modern) cadastre and flexibility for planning, environmental protection etc.. Here, it is crucial that a more efficient method of cadastral surveying should be implemented, and that the standards, specification and procedures for cadastral surveying give a high priority to speed, cost and an accuracy level. Also, at the same time, it does not jeopardize the effectiveness of the land registration system. It is therefore, the ' creation' of CCS in Malaysia is a major long-term undertaking which can systematically be implemented either in phased or incremental approach.
The procedures for both GPS test calibration gives a solution which we feel offers legal traceability and quality control checks. However, it is important to remember that the coordinate values are merely evidence as to the "legal" position indicated by the original physical monument.. Also, it should be kept in mind, the GPS method will not work in every situation. Therefore, in order to be effective, it needs to be integrated with current techniques and equipments, for example, using Total stations where GPS doesn't work (under trees or near buildings). One of the shortcomings of the proposed GPS methodology is that it cannot easily be used for setting out new points at predefined locations. Finally, to conclude this paper, we believe that the GPS technology will offer a very viable alternative to cadastral surveying approaches, such as aerial photography or total station techniques, typically adopted in large scale land administration, titling and registration projects.
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