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2. Benchmark (surveying) - Wikipedia

   en.wikipedia.org/wiki/Benchmark_(surveying)

   An Ordnance Survey cut mark in the UK Occasionally a non-vertical face, and a slightly different mark, was used. The term benchmark, bench mark, or survey benchmark originates from the chiseled horizontal marks that surveyors made in stone structures, into which an angle iron could be placed to form a "bench" for a leveling rod, thus ensuring that a leveling rod could be accurately ...

3. Reduced level - Wikipedia

   en.wikipedia.org/wiki/Reduced_level

   National survey departments of each country determine RLs of significantly important locations or points. These points are called permanent benchmarks and this survey process is known as Great Trigonometrical Surveying (GTS). The permanent benchmarks act as reference points for determining RLs of other locations in a particular country. [4] [5 ...

4. Glossary of levelling terms - Wikipedia

   en.wikipedia.org/wiki/Glossary_of_levelling_terms

   B.S is generally taken on the point of known reduced level as on the benchmark or a change point. [1] Benchmark (surveying) – fixed reference point of known elevation with respect to which RL of other points is determined. Benchmarks can be arbitrary or permanent, the former is used for calculation of reduced levels for small survey works and ...

5. Level (optical instrument) - Wikipedia

   en.wikipedia.org/wiki/Level_(optical_instrument)

   The complete unit is normally mounted on a tripod, and the telescope can freely rotate 360° in a horizontal plane.The surveyor adjusts the instrument's level by coarse adjustment of the tripod legs and fine adjustment using three precision levelling screws on the instrument to make the rotational plane horizontal.

6. Survey marker - Wikipedia

   en.wikipedia.org/wiki/Survey_marker

   Survey markers, also called survey marks, survey monuments, or geodetic marks, are objects placed to mark key survey points on the Earth's surface. They are used in geodetic and land surveying . A benchmark is a type of survey marker that indicates elevation ( vertical position ).

7. Levelling - Wikipedia

   en.wikipedia.org/wiki/Levelling

   The dumpy level was developed by English civil engineer William Gravatt, while surveying the route of a proposed railway line from London to Dover. More compact and hence both more robust and easier to transport, it is commonly believed that dumpy levelling is less accurate than other types of levelling, but such is not the case.