First published on 17 Nov 2009
In Belagavi there are two GTS (Great Trigonometrical Survey) benchmarks. The first is housed in the St.Mary’s church premises in camp and the second one is placed at the Circuit House.
GTS is the standard is for establishing the elevations of the above mean sea level from a specific reference land surface. This was established in 1907 as 2523 feet above mean sea level.
A G.T.S. (Great Trigonometrical Survey) benchmark is a permanently fixed reference survey station (or point), having known elevation with respect to a standard datum (mean sea level). These are established all over India by the Survey of India department with greater precision. A benchmark value is quite essential at any survey area, especially for the reduction of observed sea level with respect to mean sea level or chart datum (CD).
While carrying out a bathymetric survey of a survey area, the datum referenced values thus obtained are used to compute the final depth contours of the survey area (with respect to CD). So, a benchmark, having known elevation is quite essential at the survey area, without which, preparation of a bathymetric chart is impossible. In some places, GTS benchmarks are available within a kilometer distance and can be easily transferred to the survey area by fly leveling using an automatic Level instrument and a graduated leveling staff.
But in most cases, GTS benchmarks may be at a faraway distance from the area to be surveyed. In these cases, the most common traditional method of transferring the benchmark value using an automatic level instrument is a difficult task, consuming an enormous amount of time and labor. To eliminate this process, a method is suggested in this technical report to transfer the GTS benchmark from any far distance to the survey area.
The latest Electronic Total Station (ETS) is the instrument that can be used for this purpose. The main advantage of applying this method is that a considerable amount of time can be saved while maintaining the required accuracy.