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Abstract
A project to establish a system of marine geodetic controls around Japan started in 1980. Since the neighboring seas of Japan are studded with small islands, the planned geodetic control stations on these islands are expected to play a role similar to sea bottom controls. The planned system consists of about 60 island stations that cover an area of 3,000 km × 3,000 km around Japan.
The geodetic framework is defined by the coordinates of the fundamental control stations placed on ten larger islands in a geocentric system such as GRS‐80. That is, the coordinates of these stations shall be determined by laser ranging of Lageos and photographing and laser ranging of the geodetic satellite GS‐1, which is planned to be launched in 1986 from Japan. At the beginning of 1982 a laser‐ranging device was installed at one of our observatories, and observations of Lageos are successfully continuing at present.
About fifty secondary control stations are placed on smaller islands and rocks, and are connected to the nearby fundamental control stations by means of simultaneous observations of U.S. Navy navigation satellites. In 1980 and 1981 observations for this purpose were made on seven islands in southwestern Japan.