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

Wednesday, February 13, 2019

Principles of chain surveying

Chain survey belongs to the easiest method of surveying. Under this type of survey, only measurements are captured in the construction site, and the other works, like plotting measurement etc. are carried out in the office. Irrespective of angular measurements, only linear measurements are undertaken. It is mostly effective for small plane areas having very few details. If it is performed efficiently, it provides quite perfect results.

To conduct this survey, the following items are required in job site - Chain, Tape, Ranging-Rod, Arrows, Cross staff

Relevance of Chain Survey - Chain survey can be undertaken for the following purposes:

1. The area required to conduct survey is relatively small
2. The ground is level to some extent
3. The area is open and
4. Details to be gathered are simple and less.


Survey Station - Survey stations are categorized as follow : Main Stations, Subsidiary or tie

Main Stations: Main stations refer to the end of the lines, which manage the boundaries of the survey, and the lines which attach the main stations remind of the main survey line or the chain lines.

Subsidiary or the tie stations: Subsidiary or the tie stations belong to the points chosen on the main survey lines, where it is important to trace the interior detail like fences, hedges, building etc.

Tie or subsidiary lines: A tie line connects two fixed points on the main survey lines. It facilitates to verify the exactness of surveying as well as trace the interior details. The location of each tie line should be adjacent to some features, like paths, building etc.

Base Lines: It is the primary and longest line, which moves roughly through the center of the field. All the other measurements to demonstrate the details of the work are obtained relating to this line.

Check Line: A check-line also called as proof-line belongs to a line that attaches the apex of a triangle to some fixed points on any two sides of a triangle. A check-line is calculated to verify the exactness of the framework. The length of a checking line, as calculated on the ground should satisfy its length on the plan.

Offsets: Offsets stand for the lateral measurements from the baseline to secure the positions of the several objects of the work in relation to the baseline. These are normally set at right angle offsets. It is also drawn by applying a tape.

Chain survey method:
1. Reconnaissance: The initial examination of the area prepared for survey is known as reconnaissance. The surveyor examines the area to be surveyed as well as arranges index sketch or key plan.
2. Marking Station: Surveyor settles the required no of stations at areas from where maximum possible stations can be arranged.


The marking is done with the following processes:

a. Setting ranging poles
b. Pushing pegs
c. Marking a cross if the ground is solid
d. Digging and setting a stone.


3. After that, the surveyor chooses the way for transforming the main line, that should be horizontal and dirt free as possible and should move around through the center of work.
4. Then ranging roads are secured on the stations.
5. As soon as the stations are fixed, chaining should be done.
6. Create ranging wherever required.
7. Work out the change and offset.
8. Enter in the field the book.


Principles of chain surveying

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Published By
Rajib Dey
www.constructioncost.co
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Wednesday, December 26, 2018

Uses and advantages of digital theodolite in surveying & engineering works

In this exclusive civil engineering tutorial, you will learn the step-by-step guidelines for employing digital theodolite.

The surveyors extensively use this tool for conducting topographic survey. With this tool, it is possible to determine both the horizontal and vertical angle. By combining with stateo techniques, it can work out the horizontal distances as well as differential elevations. It is a useful tool for surveying and engineering work.

Theodolites apply caged graduated circles and angular readings are captured with an internal magnifying optical system.

The theodolite comprises of a telescope that can be moved within two perpendicular axes- the horizontal axis, and the vertical axis. The telescope is fixed and an electronic readout screen is applied to demonstrate horizontal and vertical angles. Digital theodolites are user-friendly since the digital readouts substitute the conventional graduated circles and produce more precise readings.

Instructions for use :-

Label the point at which the theodolite is going to installed with a surveyor’s nail or a stake. This point is considered as the base for calculating the angles and distances.

Arrange the tripod. The height of the tripod should be kept in such a way so that the instrument (the theodolite) remain in eye-level. The centrally placed hole of the mounting plate should remain over the nail or stake.

Push the tripod legs into the ground with the brackets on the sides of each leg.

Fix the theodolite by positioning it on top of the tripod, and screw it in exact position with the mounting knob.

Calculate the height among the ground and the instrument. It should be applied as a reference to other stations.

The theodolite should leveled by altering the tripod legs and employing the bulls-eye level. The slight tuning is done with the leveling knobs to secure t it just right.

Alter the small sight (the vertical plummet) available on the bottom of the theodolite. The vertical plummet facilitates you to perform and make sure the instrument is situated over the nail or stake. Modify the plummet with the knobs on the bottom.

Point the crosshairs in the main scope at the point to be calculated. With the help of the locking knobs on the side of the theodolite, retain it aimed on the point. Record the horizontal and vertical angles with the viewing scope available on the theodolite’s side.

Benefits of applying a Theodolite

Given below, various advantages of Theodolites:


  1. Superior correctness.
  2. Internal magnifying optical system.
  3. Reading circles is more accurate as compared to other instruments.
  4. Electronic readings.
  5. Horizontal circles are rapidly zeroed or arranged with any other value.
  6. Horizontal circle readings are captured either to the left or right of zero.
  7. Repeat readings are not required.
  8. Suitable for both flat and sloped ground.
  9. Not affected with wind or other weather factors.
Uses and advantages of digital theodolite in surveying & engineering works

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Published By
Rajib Dey
www.constructioncost.co
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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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