A Procedure for River Crossing in Precise Leveling.
DEFENSE MAPPING AGENCY HYDROGRAPHIC/ TOPOGRAPHIC CENTER WASHINGTON DC
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A procedure for transferring precise level across a river based on simultaneous measurement of vertical angles to targets mounted on level rods, with a Wild T-3 theodolite, and successfully employed on the Senegal River Basin Survey Project, is described. Different methods available for computing the difference in elevation from observed vertical angles are discussed, and various checks in the intermediate and the final computed results are pointed out. The results of a test comparison of the distance computed from observed vertical angles with one measured with EDM equipment is also reported. It is apparent that the instrument pointing error and the atmospheric conditions play the key roles in river crossing. The results obtained using this procedure with a T-3 theodolite are comparable to those achievable through other methods commonly used for river crossing. Author