BENCHMARK IS A PERMANENT AND TEMPORARY REFERENCE POINT IN SURVEYING. THE TERM IS USUALLY APPLIED TO ANY ITEM USED TO MARK A POINT AS AN ELEVATION REFERENCE.
TYPE OF BENCHMARK
1. GTS BENCHMARK IN SURVEYING
2. PERMANENT BENCHMARK IN SURVEYING
3. ARBITRARY BENCHMARK IN SURVEYING
4. TBM IN SURVEYING (TEMPORARY BENCHMARK)
GTS BENCHMARKS ARE ESTABLISHED BY NATIONAL AGENCIES LIKE THE SURVEY OF INDIA DEPARTMENT AT A LARGE INTERVAL ALL OVER THE COUNTRY ( 100 KM. INTERVAL). THEY ARE ESTABLISHED WITH THE HIGHEST PRECISION. THEIR POSITION AND ELEVATION ABOVE MSL ARE GIVEN IN A SPECIAL CATALOGUE KNOWN AS GTS MAPS.
A PERMANENT BENCHMARK IS A FIXED POINT OR MARK ESTABLISHED BY DIFFERENT GOVERNMENT DEPARTMENTS LIKE PWD RAILWAY, IRRIGATION ETC. THE RLS OF THIS POINT IS DETERMINED WITH REFERENCE TO THE GTS BENCHMARK AND IS KEPT ON A PERMANENT POINT.
ARBITRARY BENCHMARK RLS OF SOME FIXED POINTS ARE ASSUMED(100M), THEY ARE TERMED ARBITRARY BENCHMARKS. THESE ARE ADOPTED IN SMALL SURVEY OPERATIONS.
Temporary Benchmark
WHEN THE BENCHMARKS ARE ESTABLISHED TEMPORARILY AT THE END OF A DAY’S WORK, THEY ARE SAID TO BE TEMPORARY BENCHMARKS. THEY ARE GENERALLY MADE ON THE ROOT OF A TREE, THE PARAPET OF A NEARBY CULVERT ETC.
