The accuracy Df a few centimeters oan be easily obtained in 2drms of the horizontal positions by R. TK − GPS positioning . It is necessary , however , to provide tho carrier phase data丘o 皿 a reference station looated at a known position, to a user rcceiver . It is hard to purchase the expensive GPS receiver for RTK − GPS . So , the RTK − GPS users in Japan have desired the develop 皿 e 皿t of a 皿 ore flexible , wider and less expensive carrier phase data dissemination service fbr a long time . In

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... Japan , the area correction parameter FKP ( flachen −korrectur − parameter ; Geo++ in Germany)method has been well tested and evaluatcd through 皿 any pr〔 ) jects nationwide , such as the mobile ! cellular phone ofthe dual directional communication . Now , using the SuperBj エd geostationary satelli偽 coMml 皿 ication lino , correction data transfer for ・ the user station has tested on the RTK − GPS positioning at a fixed