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Showing posts with label Engineering Survey. Show all posts
Showing posts with label Engineering Survey. Show all posts

Monday, July 23, 2018

Setting out survey process – Definition and various benefits

Setting survey process is applied to set out the exact position of a projected structure inside the legal boundaries of a plot of land.

The objective of setting out is to set out perfect position & levels of building lines and road alignments for a projected structure as per construction plans by applying different techniques and instruments.

This type of survey is very vital while going to set up any type of construction work.

Generally, a set-out survey comprises of the process for transforming a building design onto the land itself in order that the builders can abide by the process throughout construction. Throughout the process, major points are set up and markers are applied for the progression of the building process and maintain perfectness.

For large scale projects like high rise buildings and developments, multiple set-out surveys are required as the construction advances. This type of survey is mainly undertaken for the earthworks, roads, car parks, sewerage, water and the actual buildings themselves.

Methods of Setting Out Survey


1. Setting out buildings by coordinates
2. Setting out with theodolite and level
3. Examining verticality
4. Setting out and alignment in steel framed buildings
5. Alignment and verticality in form work
6. Control and computation for route surveying
Setting Out Building by Coordinates
A building is set out by adopting referencing from an already established baseline. An asymmetrical building or a building with complicated geometry can also be established by applying the equivalent process. For each corner of the building, a grid line is set up from the baseline.
Examine Verticality - The verticality of points in a building is examined with the following surveying instruments:
1. Plumb Bob (For buildings less than 20m in height)
2. Optical Plummet (A transparent plastic sheet is used as a target for checking verticality of tall buildings)
3. Theodolite
Setting out Survey works also contains the following :-
Calculations and setting out Methods for:
1. Simple Circular Curves
2. Compound Curves
3. Reverse curves
4. Transition curves
5. Vertical curves
To get more details, go through the following video tutorial
Video Source: Finchley College

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Published By
Rajib Dey
www.constructioncost.co
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Tuesday, June 26, 2018

Brief overview of rise and fall table in land surveying

This construction video tutorial is very useful for land surveyor. The tutorial sheds light on the rise and fall table in land surveying. Get some useful tricks to resolve the rise and fall table.

Rise and fall method is applied to resolve the levelling to detect the variation in elevation and elevation of points..


By resolving this table, it is possible to work out the reduced level of each point captured at staff rod with leveling machine. In order to work out the reduced level of an individual point, it is necessary to compute the rise and fall of points. After that, for reduced level, the following formula is applied :-

new R.L = old R.L – Fall
new R.L = old R.L + Rise


The table contains various heads like number, B.S (back sight), I.S (inter sight), F.S (fore sight), Rise, Fall, R.L (reduced level) and remarks.

B.S - Back sight (BS) is the abbreviation for "back sight reading". It means the first staff reading captured by the surveyor as soon as the levelling instrument is arranged and levelled. B.S is normally captured on the point of known reduced level as on the benchmark or a change point. The normally applied datum is mean sea level.

Fore sight (FS) is the abbreviation for "fore sight reading". It means the last staff reading captured prior to modify the instrument to the other position. It refers to the staff reading captured on point whose RL is to be ascertained. This sight is treated as negative and assumed from Height of Instrument to find out RL of the point.

Reduced Level (RL) in surveying stands for equating elevations of survey points relating to a common assumed datum. It refers to a vertical distance among survey point and selected datum plane. Therefore, it is taken as the base elevation that is applied as reference to consider heights or depths of other important places.

To get more detailed information, watch the following video tutorial.




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Published By
Rajib Dey
www.constructioncost.co
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