Understanding Bench Marks in Surveying
Bench Marks (B.M) serve as fixed reference points with known elevations, essential for starting any leveling work. They can be categorized into GTS, Permanent, Temporary, and Arbitrary types, each serving specific purposes in surveying projects.
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Presentation Transcript
Bench Mark (B.M) It is a fixed reference point whose elevation with respect to some datum is known. It is noted that any leveling work is first started from BM.
Types of Bench Mark 1. GTS (Great Trigonometric Surveying) 2. Permanent 3. Temporary 4. Arbitrary
1. GTS GTS are establish in Pakistan by fedral government department. Survey conduct in all over the country at large interval may be 100- 150 km. These bench marks are highly precise.
2. Permanent This type of bench mark is establish by Irrigation department, Communication & Work department, highway department and Railway department. These are also establish with the help of GTS.
3. Temporary These are establish temporary after on day working. So, next day work can start from there.
4. Arbitrary In many engineering projects the difference in elevations of neighboring points is more important than their reduced level with respect to mean sea level. In such cases a relatively permanent point, like plinth of a building or corner of a culvert, are taken as benchmarks, their level assumed arbitrarily such as 100.0 m, 300.0 m, etc.
