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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Get some useful tips to conduct your leveling survey at home

While going to layout something for road, bridge, dam or pipe line, land surveying plays an important role. Surveying is done to find out the legal boundaries among the parcels of property, the position of current infrastructure, the topography as well as slopes of the land.

Traditional measurement tools like a tape measure and protractor are not suitable for accomplishing large civil structures and public works projects.

In this construction video tutorial, Mr. Grady shows some useful tips which will help you to conduct your own topographic or leveling survey at home with fairly elementary and cost-effective tools. You don’t require any knowledge with sines, cosines, or tangents.

To learn the complete process, go through the following video tutorial.

Video Source: Practical Engineering

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Published By
Rajib Dey
www.constructioncost.co
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How verticality of structure is checked during construction

It is essential to verify the verticality while building up the construction at various phases like setting up vertical formworks of columns and transmitting levels up succeeding floors of multi storey structures.

Different types of processes are used to manage or verify verticality works throughout building construction which are explained below :-

The following processes are followed to verify or manage verticality works:

1. Plumb-Bob Technique: Plumb-bob comprises of a weight having pointed tip on the bottom connected with the end of a string. The heavy weight will suspend under gravity and provide a perfect vertical line that is known as plumb line.

This process is useful for examining or managing vertical line of structural elements specifically indoors like lift shaft. With the addition to that, it gets the ability to manage verticality of foundation, walls, and columns.

The wind force affects the plumb line or vertical line of plumb-bob and it’s perfectness can’t be retained. Small to medium lateral movement of plumb-bob can be decreased favorably by moistening it in oil or water.

If structural member’s height is extensive, then the string can be substituted with a long wire, but persistent cautions should be plasticized to get rid of imposing risks to the personals working below.

2. Spirit Level Method: This tool is very suitable for managing verticality of small scale works as for instance verifying formworks and door frames. If spirit level is applied for approximate checks, then it becomes essential to examine the verticality with more precise technique.

3. Theodolite Method: Theodolite is considerably robust instrument that can be utilized to verify the verticality works throughout construction by maintaining exactness and correctness.

It is undertaken for examining or managing verticality of towers, wall, foundation and columns; specifically huge number of columns along a one grid line.

The slope out of plumb line of the member can be calculated with Theodolite in conjunction with a tape.

The following methods are applied to examine the verticality of column:

a. Arranging the digital Theodolite to the center on a peg that installed 500 mm from the column grid.
b. Once set up is completed properly, the laser beam will be activated and concentrated it to the steel tape that is retained to the formwork.
c. Obtain the reading of the steel tape via the telescope.
d. Obtain the readings of two positions at the equivalent level on both top and bottom levels of the formwork. With two readings at the equivalent level, it will be possible to recognize any curvature on the surface.

4. Optical Plummet Method: It is a useful tool that sight directly down or directly up. There is an automatic compensator in optical plummet that enhances its precision drastically concerning other methods applied for managing verticality.

Article Source: theconstructor.org



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Published By
Rajib Dey
www.constructioncost.co
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