By:- Kamaluddin Hj.Talib, Mat Akhir Md.Wazir, Othman Yusof Khairul Nizam Tahar

1. EVALUATION AND DETERMINATION OF COORDINATES UNDER CANOPY USING DUAL FREQUENCY GPS. CASE STUDY: MALAYSIAN NATIONAL PARK (TAMAN NEGARA) By:- Kamaluddin Hj.Talib, Mat Akhir Md.Wazir, Othman Yusof Khairul Nizam Tahar

2. ABSTRACT • The objective of this study is to evaluate the accuracy of dual-frequency GPS receiver in the static-surveying at different forest canopies and environment and to develop a suitable observations technique in order to determine the control coordinates at Taman Negara. Finally, the precision and accuracy of GPS positioning (horizontal and vertical) will be calculated, compared and analysed. Eventually the result derive from the observation (φ, λ, h or bearing & distance) can be used as a reference coordinate (datum).

3. INTRODUCTION Malaysian National Park (Taman Negara) is located north of Pahang bordering the state of Kelantan and Terengganu. The gateway town of Taman Negara is Kuala Tahan and is situated about 220 km away from Kuantan (capital city of the state of Pahang, Malaysia).

4. Taman Negara Environment a) b) Land view Sky view c) Bird view.

5. RESEARCH METHODOLOGY Selection of GPS Station and Control Point Observation Obs. Technique: Radial Static Duration: 2 hrs Sync: 15 sec Elev: 15 deg PDOP: 4 GPS Stations Observation and Heighting Observation Obs. Technique: Static/Fast Static Dual/Single GPS used Duration: 1 hr, 30 min and 15 min Sync: 15 sec PDOP: 4 Data Processing and Analysis. Evaluation by comparing Single and Dual Freq. data Result and Discussion Figure 3.0: Methodology flow chart of observations procedure using GPS technique

6. From Figure 3.0, the GPS Observation station (Stn1) were established from GPS261, Dept. of Surveying & Mapping (DSMM) GPS Geodetic Control Network Station (JUPEM 1994), using Radial Static observation (Sickle 2001) for the duration of 2 hours. Heighting of the station is done by GPS levelling technique (US Army 1998 and Abd Majid et.al 1997) transferred from Government Bench Mark (JUPEM 1994) located about 75 km away. The observation is done in 3 loop (about 25 km spacing) using dual frequency GPS for the duration of 1 hour for each loop (Table 1.0)

7. Table 1.0: Coordinate of Stn1 transferred from GPS261 & BM C3247 (2 hrs. Obs)

8. OBSERVATIONS RESULTS AND ANALYSIS For the purpose of canopy effect study, field observations were conducted. Three (3) GPS points were selected and marked on the ground (Figure 4.0). GPS observation is based the on Differential Radial Rapid Static method (Sickle 2001) using Single/Dual Frequency GPS.

9. a) Stn1 Stn1 with large canopy gap, b) Stn2 Stn2 with small canopy gap c) Stn3 Stn3 with closed canopy

10. Table 2.0: Result of canopy effect from Single (L1) Frequency GPS data From Table 2.0, it is found out that the error in bearing, distance and height increases as the observation duration decreases.

11. Table 3.0: Result of canopy effect from Dual (L1/L2) Frequency GPS data From Table 3.0, it is also found out that error increases as duration of observation decreases. For short distances determination, it seem that, single frequency GPS give a better result than dual frequency GPS.

12. REMARKS AND CONCLUSION In the study, height analysis are based on height above WGS84 ellipsoid, with the knowledge of geoid-ellipsoid separation (geoid undulation), orthometric height can be determine or transfer. Bearing differences are calculated after transformation to MRSO. From the analysis of the data, for observation of short distances (<500m) under forest canopies, either single or dual frequency GPS can be used with at least half an hour duration.

13. Comparing the result, the quantitative analysis represents a useful tool to define the most suitable technique for the determination of coordinates under forest canopies. This data can be used as a guide for researchers and surveyors and also for the general planning of current and future development of the area related to mapping of Taman Negara.

14. REFERENCES • Abd. Majid, A.K., Samad, A. dan Fashir, H.H. 2000. Progress Toward Examination of Datum Transformation Parameters Between WGS84 in Peninsular Malaysia, South African Journal of Surveying and Geo-Information, Jilid 1, No.4, April. hlm.191-204. • Abd. Majid, A.K., Samad, A. dan Shahrum, S. 1997. Preliminary Analysis of Precise Levelling Network for the Southern Peninsular Malaysia, Buletin Geoinformasi, Jilid 1, No.1, UTM. • JUPEM, 1994.GPS Derived Coordinates, Report of the Geodesy Unit, Topographic Section, Department of Survey and Mapping Malaysia. • Rizos. C., 1997. Principle and Practice of GPS Surveying. Monograph 17, School of Geomatics Eng., UNSW. Australia. • Sickle, J.V., 2001.GPS for Land Surveyors, 2nd Edition, Taylor & Francis, New York. • Talib, K.H. 2002. Reliability of High and Low End GPS in Demarcation Survey, 3rd Malaysian Remote Sensing and GIS Conference and Exhibition, Kuala Lumpur. • U.S. Army, 1996.Navstars Global Positioning System Surveying, Department of the Army, U.S. Army Corps of Engineers, Washington, DC. • U.S. Army. 1998, Using Differential GPS Positioning For Elevation Determination, Engineering Manual, U. S. Army Corps of Engineers, Washington, DC. • Wolf, P.R, and Dewitt,B.A.,2000.Element of Photogrammetry with application in GIS, 3rd.edition, McGraw-Hill.

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