Bench Mark

A bench mark (BM) is a fixed (permanent) reference point of known elevation. This bench mark is used as a base associative to that the elevations or levels of different points in a survey are measured. This could be

(a)        GTS bench marks

(b)       Permanent bench marks

 (c)       Temporary bench marks

(d)       Arbitrary bench marks

GTS bench marks are building precisely and accurately and are used as base for all levelling exercises, particularly when large areas are to be surveyed. Reference bench marks fixed in a field on permanent structure are known as permanent benchmarks. These are used for reference and future surveys to give continuity. In little levelling works, the decreased level of a well defined reference point is supposed as arbitrary benchmark of levels. During the levelling exercise, while there is a break of work continuity, temporary bench marks are build to give continuity while the survey is resumed.