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What is the Importance of Benchmark Shifting in Land Surveying?
Bench marks are permanent markers set at a recognized elevation to be used as a basis for determining other topographic points' elevations in surveying. A spot height refers to an elevation that is marked on a map but not physically marked on the ground.
Benchmark shifting entails referencing an old recognized point to determine the level of a newly situated point.
Basically, a benchmark is a reference point from which one can calculate something. Bench marks in surveying are permanent posts or marks that are set at a certain elevation and used to calculate the elevation of other points on the ground.
Construction Process of Benchmark
An angle iron is set into horizontal chiseled marks that surveyors make in stone structures to create a bench for a leveling rod, so that it can be properly repositioned at the equivalent spot in the future.
Thus, the name bench mark, or benchmark, was derived from chiseled horizontal marks created by surveyors in stone structures. A chiseled arrow is generally carved under the horizontal line to point to these marks.
As a reference to elevation, the term is usually applied to anything that marks a point. In order to provide a secure position for elevation, bronze or aluminum disks are often embedded in stone or concrete, or on poles driven deeply into the earth.
Define Benchmark Shifting
In land surveying, benchmark shifting refers to the adjustment of an elevation on a benchmark, which is a permanent reference point used for determining heights and elevations.
A benchmark shift is the process of determining a new point's level based on an old known point. The shift of benchmarks should only be performed by qualified and experienced surveyors to ensure accurate and reliable measurements.
Benchmark Shifting Causes
Changing Vertical Datums
When it comes to the surveying of land, benchmark shifting may be required for a variety of reasons. Changing vertical datums, which are used as a reference surface to measure elevations, account for one of the reasons.
As surveying technology improves or the Earth's surface changes due to natural or manmade factors, the vertical datum may change. Whenever the vertical datum changes, benchmark elevations must be adjusted to ensure that all survey measurements are accurate and consistent.
Benchmark Physical Location Change
The physical location of a benchmark can also cause benchmarks to shift. The benchmark may be disturbed or destroyed as a result of construction or development projects. To ensure consistency with the old benchmark, a new benchmark may need to be established and its elevation may need to be adjusted.
Benchmark shifting is typically carried out by measuring the elevation difference between the old and new benchmarks using a process called differential leveling. Add or subtract the difference in elevation between the new benchmark and the old benchmark to adjust its elevation to match.
Importance of Benchmark in Land Surveying
The height of the land and the height of the sea level should be taken into consideration by surveyors when creating floodplain maps. In order to assess whether the land changes over time, it is beneficial to use the same benchmark for successive surveys. To tell insurance providers what plans are more susceptible to damage, you can notice if the earth is shifting.
With specific datum measurements taken from the same site, you can determine erosion, earthquake prone areas, flood danger areas, mudslide danger areas, and much more.
Understanding what type of survey to conduct, where to conduct it, and when to conduct it will help us create better construction surveys, property boundary lines, dam designs, and ensure our measurements are consistent.
To get more details, go through the following video tutorial.
Lecturer: Engineer Boy
To achieve the highest level of accuracy and safety, benchmarks and datums must be used properly.
Providing accurate measurements and reliable data is crucial to keeping construction crews and service people safe. It is necessary for a surveyor to know how to utilize these things to their best advantage.
