Determination of the Mean Sea Level and Establishment of the 1st Order Levelling Network in Bangladesh.

概要

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A fundamental geodetic survey over Bangladesh was carried out by a Japanese Survey team headed by Dr. Tajima with Survey of Bangladesh (SOB) from 1992-1995. Levelling survey and tidal observations were carried out to determine the height of the 461 bench marks along the 2, 386 km leveling route. The mean sea level of the Bay of Bengal was determined through 2 years of tidal observations by a tidal gauge installed at the mouth of the Karunafuri River in Chittagong City supported with observations from an auxiliary pressure type tidal gauge installed offshore of Chittagong. The levelling survey was eecuted with bar-xcode levels on the general surveying route. However, river crossing levelling was carried out by the tilting screw method and reciprocal levelling, depending on the length of sight. Two sites of river crossing levelling done by the tilting screw method were compared with the results by levelling over the bridge constructed afterward and the results coincided very well. Adjustments after the entire all survey revealed that the levelling observation was done very accurately, of which standard deviation for the unit weight (1 km) is as small as 0.9 mm. The height of vertical datum is determined as 6.4292 m from the results of these tidal observations and levelling surveys.
日本測地学会の論文