|
|
|
Cadastral reform in Malaysia: A vision to the 2000s
- GPS Cadastral Survey Test
A GPS cadastral survey on the selected areas (sites) were carried out using rapid-static technique. The test survey is divided into two cases:
CASE (i) A 'new cadastral survey lot' using conventional traverse and GPS observations,
CASE (ii) Adjacent lots which is comprised of existing standard traverse cadastral.
The rapid static field observation criteria adopted for both cases is shown in Table: 2.
Table 2: The Rapid Static GPS Observation Criteria
| ITEMS |
CRITERIA |
| Observation span |
10-15 minutes |
| Recording Interval |
15 seconds |
| Number of satellites |
³ 5 |
| GDOP |
£ 5 |
| Sky coverage |
³ 70 % |
| Mask angle |
15° |
For CASE (i), the survey were done using three (3) Leica dual frequency GPS receivers with two (2) of them remained at base stations and another one is roving receiver. The survey was planned so that all selected traverse stations were occupied successively by the roving receiver. The calibration is performed in order to ensure the correct operation of GPS receivers, associated antennas and cabling, and data processing software, give high accuracy coordinates results (as described in the previous sections). In CASE (i), a sample GPS cadastral control survey has been carried out in UTM campus. The test survey site is comprised of fourteen (14) traverse stations. The conventional traversing method and GPS observations were carried out to determine the coordinates of the traverse points using total station GTS-7 and Leica 300, respectively. Two (2) GPS base stations BC10 and G11, were used as control points for the traverse survey. These stations were previously connected to the National 1st. Order GPS Network. In the processing step, data from 10-15 minutes observation session has been used. The adjustment is being carried out using SKI software with station BC10 and G11 being held fixed. The resulting coordinates were then being transformed into their corresponding values in local MRT, RSO and CS coordinate systems. The area of the traverse survey is also being computed using the adjusted coordinates (in CS system).
For CASE (ii), the test area is chosen closed to the existing cadastral standard traverse. The survey area is comprised of six (6) cadastral lots, namely 2290, 2291, 2292, 2294, 2296 and 2298. These cadastral lots have been surveyed in 2nd. class survey requirements. The GPS control observations is being carried by connecting two standard traverses stations, MC858 and MC904. The corresponding CS system for station MC858 and MC904 is (S59902.881, E60183.967) and (S60989.321, E62460.282), respectively. Since, the spacing between the two stations are less than 10km apart, they are very suitable to provide control for the proposed GPS cadastral survey on the selected lots which will be carried out using rapid static technique. Also, these stations were previously 'connected to the National 1st Order GPS Network' via two (2) standard cadastral traverse stations (KGPB and MC793. Again, as for CASE (i), the surveys were done using three (3) receivers with two (2) of them remained stationary at these base stations. One receiver is roving successively to occupy fourteen (14) boundary marks whereby two base stations are used to provide independent check on the resulting GPS coordinates for each boundary marks. The GPS network adjustment has also been carried out in WGS84 using SKI software with stations MC858 and MC904 being held fixed. To make the GPS coordinates meaningful, they are then converted into a locally useful system, i.e. MRT, RSO and CS systems. From the GPS-derived CS coordinates, the distance and bearing between the traverse legs were computed. The next step is to make the comparison between these adjusted coordinates and the corresponding Certified Plan (CP) values. Further exercise has also been done by calculating the area for individual lot and comparing them with their corresponding values shown on the CP.
|
|
|