Geodetic Activities in Indonesia

Transcription

1 Journal of the Geodetic Society of Japan Vol. 30, No. 1, (1984), pp Geodetic Activities in Indonesia Joenil KAHAR Department of Geodesy, The Institute of Technology of Bandung, Indonesia ABSTRACT Primary triangulation network of Jawa was started in 1862 and completed in This network was computed in a system which was called Genuk System. This network was extended to Sumatera and Nusa Tenggara Isles and the computation in the Genuk System for those area was started in Beside this system there were two other systems, Malayan System for Bangka, Riau & Lingga and Serindung System for West Kalimantan. A unified datum was established after a Doppler satellite observation held in Padang, and the datum was called the Indonesian Datum 1974 (ID-1974). Determination of geoid in the Indonesian Archipelago was worked out by combining a global detailed gravimetric geoid computed by March & Chang (1976) and the oceanic geoid derived from GEOS-3 altimetry data (Rapp, 1979). A new precise leveling network in Jawa has been designed and measured since The measurements of this network will be completed in 1985, so that the measurements may be continued to Sumatera. Principal gravity base stations were established through a joint working between the Geological Survey of Indonesia and the University of New England, Australia. 1. Introduction Before the Second World War the mapping activities (the establishment of the hori zontal and vertical networks were included) in Indonesia were responsibility of the Topo graphical Service of the Netherland East Indies. After the Second world War the Topo graphical Service of the Army of the Republic of Indonesia took over the responsibility. In 1969 the President of the Republic of Indonesia established "Badan Koordinasi Survey dan Pemetaan Nasional" (the National Coordination Agency for Surveys and Mapping), abbreviated BAKOSURTANAL. The main function of this organization is to advise the Republic of Indonesia on matters related to surveys of natural resources and mapping of the national territory. It is the responsibility of BAKOSURTANAL for the production of national topographic base map series including sea bottom topography, the establishment of national geodetic control, the delineation and survey of the international land as well as seaward boundaries and the coordination of hydrographic survey and nautical charting (BAKOSURTANAL, 1980). * Read at 60th meeting of the Geodetic Society of Japan in October 1983.

2 62 Joenil KAHAR 2. Horizontal network Mapping activities in Indonesia started more than one hundred years ago. Jawa island as a densely populated island was given top priority. The primary triangulation of Jawa started in 1862 and was completed in The initial point which was needed for computation of this network was a triangulation point P. 520 at Gunung Genuk in Central Jawa. The parameters of the Bessel 1841 spheroid were used to define geodetic datum. The observed astronomic latitude at P. 520 and astronomic azimuth from that point to a reference object were defined as geodetic latitude and geodetic azimuth. The geodetic longitude, however was obtained by defining the astronomic longitude of P. 126 in Jakarta. The geodetic longitude of P. 520 was found by tranferring the astronomic longitude of P. 126 by triangulation computation. The geoid-spheroid separation at the initial point was defined zero. The geodetic coordinates of P. 520 at Gunung Genuk are latitude : 6ß 26' 53.4" S longitude : 110ß 55' 02.05" E The triangulation network was extended to Sumatera. Until 1931 there were three geodetic systems in Sumatera, these being the West Sumatera System, the East Suma tera System and the South Sumatera System, computed on the Bessel spheroid. Each of them has its own orientation and its own linear basis. Therefore in 1931 it was decided to make a second adjustment, including not only the Sumatera triangulation but also the triangulation of Jawa and Nusa Tenggara Isles. For this purpose a number of Laplace stations were determined, and some new base lines were measured (SCHEPERS & SCHULTE, 1931). The coordinates were computed in the Genuk System. But the computation was not completed yet, because the explotion of the Second World War. In 1960 the triangu lation measurements were extended and computed to Flores in Nusa Tenggara Isles (SOENARJO, 1962). The primary triangulation of Bangka was started in At the end of 1938 this triangulation network was connected to the Malayan System by the triangulation of Riau & Lingga (SCHEPERS, 1939). In 1970, West Kalimantan was started to be mapped. The triangulation network for this purpose was computed on the Bessel 1841 spheroid. A triangulation point at Gunung Serindung in the North of Singkawang was used as the initial point (HAUI, 1975). As the matter of fact, after the Second World War there were many triangulation points damaged. Therefore for the purpose of the Sumatera mapping project, the horizontal control in this island was determined by Doppler satellite positioning technique. Some important decisions made by BAKUSURTANAL were the adoption of the geometric parameters of GRS-67 as the parameters of the Indonesian National Spheroid (INS), and defining a Doppler station in Padang (West Sumatera) as the initial point of a new geode tic system (RAIS, 1975), and it was called Padang System. Later this system became known as the Indonesian Datum 1974, abbreviated ID-1974 (RAIS, 1979). The geodetic

3 Geodetic Activities in Indonesia 63 coordinates of the initial point are latitude : 0ß 56' " S longitude : 100ß 22' " E height : meters above INS The center of the INS is translated from the center of the Doppler NWL-9D system by the values X= m Y= m Z= m The above values are obtained by defining the INS and the spheroid of Doppler NWT,-9D system tangential at the initial point. SUTISNA (1982) computed the triangnlation of Sumatera and Jawa in ID-1974 and GEM-8 geoid was used as a reference geoid. In the period of , a 378 Doppler station was established in the Indonesian Archipelago (RAIS, 1977, 1979; THOMSON & RAIS, 1982). They were 15 stations in Suma tera, 87 stations in Kalimantan,133 stations in Sulawesi, 9 stations in the Nusa Tenggara Isles, and 134 stations in Irian Jaya. The determination of a number of Doppler stations in Jawa will be completed at the beginning of Figure 1 shows the main islands of the Indonesian Archipelago. 3. Indonesian geoid Because of the lack of the gravity data in the main islands (except in Jawa), gravi metric geoid of this archipelago is not determined yet. After the launching of GEOS-3 satellite, a global oceanic geoid was derived from the altimetry data of the satellite (RAPP 1979). The accuracy of the oceanic geoid is better than } 1.0 m. The oceanic geoid will, dominate the geoid in the area, so that this geoid may be assumed as the "true" geoid. By using a global detailed gravimetric geoid which was computed by MARSH & CHANG as an approximate geoid, an altimetric-gravimetric geoid in the main islands of the Indonesian Archipelago is determined by adding predicted correction to the approximate gravimetic geoid. The correction is predicted from the difference between the oceanic geoid and the gravimetric geoid in oceanic area. By assuming the accuracy of the MARSH & CHANG geoid is ±3 meters, the estimated accuracy of this altimetric-gravimetric geoid is better than }4.8 m. A complete development of the geoid determination can be found in KAHAR (1981, 1982). Figure 2 shows the Indonesian geoid. To improve the accuracy of this geoid, gravity survey at the whole islands of Indonesia should be completed. 4. Vertical network The precise leveling network of Jawa was started in There was only 4500 km of leveling circuit completed in West Jawa and Central Jawa with total number of points

4 64 Joenil KAHARFig. 1 Indonesia Archipelago.

5 Geodetic Activities in Indonesia 65

6 66 Joenil KAHAR

7 Geodetic Activities in Indonesia 67 was This network was tied to a sea level datum in Tanjung Priok (the harbour of Jakarta) which was derived from tidal observation during Besides the above mentioned network, there were numerous local leveling networks. There was no uniformity of these local networks. Some of them were related to a mean yearly sea level, others to mean high or mean low tides or even to the highest high tide or the lowest low tide. The accuracy of the local networks varies widely. Because of a great number of benchmarks of the precise leveling network were lost and damaged, and the relation between the various local systems were not known, then in 1980 BAKOSURTANAL started to re-measure the precise leveling network in Jawa which will be completed in BAKOSURTANAL has also designed a vertical network for the island of Sumatera. The accuracy of this network will be considered as the second order network, and the measurement will be held after the leveling network of Jawa is completed. Figure 3 shows the planned circuits of the leveling network in these islands. Discussions about the problems which are related to the vertical networks in Indonesia can be found in RATS (1980) and also in MIRA (1980). 5. Gravity survey The gravity survey in Indonesia is responsibility of the Geological Survey of Indo nesia. To date, the survey in the islands of Jawa, Bali and Madura have been completed and results of work in the Nusa Tenggara Isles will be completed soon. The regional base stations were established under a joint program funded by the Ministry of Mines of the Republic of Indonesia and the Australian Goverment through the Australian Research Grants Commission and the Australian Development Assistance Bureau. The program was worked out by the Geological Survey of Indonesia and the Departement of Geophysics, the University of New England, Australia. Primary base stations for the gravity survey were established at Bandung, Jakarta, Denpasar (Bali) and these were directly tied to IGSN'71 gravity stations in Australia and Singapore. Around these primary stations, a network of some sixty-one regional base stations was established. Most of the stations are located in Indonesian airport. A complete report about the regional base stations was written by ADKINS, et al (1978). A gravity survey at Kepala Burung, Irian Jaya was also worked out under the joint program (UNTUNG, 1983). 6. Acknowledgements This paper is prepared under a research program at the Earthquake Research In stitute, the University of Tokyo which is sponsored by the Japan Society for the Promo tion of Science and the Directorate General of Higher Education, Ministry of Education and Culture of the Republic of Indonesia. I would like to acknowledge my gratitude to Dr. Yukio HAGIWARA, Professor in Geodesy at the Earthquake Research Institute, the University of Tokyo, for his valuable contributions on preparing this paper.

8 68 Joenil KAHAR References [1] ADKINS, J., SUKARDI, S., SAID, H., UNTUNG, M. (1978) : A Regional Gravity Base Station Network for Indonesia. Publikasi Teknik-Seri Geofisika No. 6, Geological Survey of Indonesia. [2] BAKOSURTANAL (1980) : Cartographic Activities in Indonesia Country Report presented at the Ninth U. N. Regional Cartographic Conference for Asia and the Pacific, New Zealand. [3] HADl, S. (1975) : Proses Pemetan Topografi Skala 1: 55,000 di Kalimantan Barat. Paper presented at the Symp. Peranan Geodesi Dalam Inventarisasi Sumber Daya Alam, Bandung. [4] KAHAR, J. (1981) : The Altimetric-Gravimetric Geoid in the Indonesian Region. Aust. J. Geod. Photo. Surv., No. 35, pp [5] KAHAR, J. (1982) : Geoid Determination in Archipelagic Area. Proc. of the General Meeting of I. A. G. Special Issue of J. Geod. Soc, of Japan. [6] MARSH, J. G., and E. S. CHANG (1976) : Global Detailed Gravimetric Geoid. Paper presented at the Fall Annual Meeting of the A. G. U., San Fransisco, California. [7] MIRA, S. (1980) : National Vertical Control Networks in Indonesia. Paper presented at the 2nd Inter national Syrnp. On Problems Related to Redefinition of North American Vertical Geodetic Networks, Ottawa, Canada. [8] RAIs, J. (1975): The Problems of Datum Selection for Surveys and Mapping. Dokumen No. 03/1975, BAKOSURTANAL. [9] RAIS, J. (1977) : The Present Geodetic Activities in Indonesia. Proc, of the International Symp.on Regional Geodetic Networks for the Year 2000, Bandung. [10] RAIS, J. (1979): Doppler Surveying in Indonesia ( ). Paper presented for the I. A. G. at the XVII IUGG General Assembly, Canberra. [11] RAIs, J. (1980) : The Status of and Problems Associated with Vertical Control Networks in Indonesia. Paper presented at the 2nd International Symp. On Problems Related to Redefinition of North American Vertical Geodetic Networks, Ottawa, Canada. [12] RAPP, R. H. (1979): Global Anomaly and Undulation Recovery Using GEOS-3 Altimeter Data. Ohio State University. [13] SCHEPERS, J. H. G. (1939) : Geodetic and Astronomical Operation in the Netherland East Indies. Report to IUGG General Assembly, Washington. [14] SCHEPERS, J. H. G., & F. C. A. Schulte (1931) : Geodetic Survey in the Netherland East Indies. Report to Section Geodesy, IUGG. [15] SOENARJO, J. (1962): Perataan Triangulasi Utama Nusa Tenggara Bagian Barat. Seri B: Publikasi Nr. 1/1962, Dinas Geodesi, Dit. Top. AD. [16] SUTISNA, S. (1982): Perataan Jaring Geodesi Horizontal 1981 Untuk Sumatera-Jawa-Nusa Tenggara Pada Sistin ID Dok. No. 25/1982, BAKOSURTANAL. [17] THOMSON, D. B. & J. RAIS (1982): The Indonesian REAP Doppler Satellite Network. Dok. No. 24/1982, BAKOSURTANAL. [18] UNTUNG, M. (1983) : Private Communication.