Describe the method of booking field notes. Explain obstacles to chaining and methods to overcome the same. Explain the methods of plotting chain survey data. Chain surveying is the type of surveying in which only linear measurements are The main principle of chain surveying or chain triangulation is to provide a. Learning Objectives. After studying this unit, the student will be able to understand. • Chain surveying and purpose of the equipment. • Studying the metric chain.
|Language:||English, Spanish, Hindi|
|Distribution:||Free* [*Registration needed]|
Chain surveying is the easiest type of survey is discussed in this post. The procedure of the chain survey, the method of over come when. CHAIN AND TAPE SURVEY GELB TOPOGRAPHIC SURVEYING 3/19/ Department of Geography and Environment Md. Tarikul Islam Chain and Tape. Teacher Notes and Instructions for Chain Surveying Activity. This activity requires a minimum of four children in the active roles but works with groups of eight to.
Try to do the following: Closed Obstacles Pond b. Linear Obstacles River a. Linear Obstacles River b. Linear Obstacles River c.
Flag for inappropriate content. Related titles. Jump to Page. Search inside document. Chain Surveying Dr.
Uneven Ground. Choice of Chain Lines As close as possible to the buildings.
Choice of Chain Lines At least two stations can be seen. Choice of Chain Lines Provide check line possibility. Choice of Chain Lines Avoid obstacles. The Parallel Method.
They are used for making chain length on the ground. Ranging Rods: They are about 10 ft. Long, 1. Offset Staff: They are wooden rods 10 feet long. Each foot is painted black and white alternately. They are used for measuring short lengths.
It consists of a wedge-shaped hollow brass box of about 2 inches sides and 1. Two plane mirrors set at 45 degrees are fixed to the inclined sides of the box.
There are two slits above these mirrors. In using it, a ranging rod is held at an object for. Which an offset is to be taken.
A man is holding the optical square in his right-hand stands on the chain line. He looks towards the front ranging rod on the chain line with the open face of the optical square towards the ranging rod at the object. Now the man looks through one mirror while the other mirror is turned towards the object.
Then he walks along the chain line forwards and backward till he sights the image of the ranging rod at the object in the mirror and the front ranging led in the slit in the same line. The position of the man on the chain line gives the exact point at which the perpendicular from the object meets the chain line. Procedure of Chain surveying: The entire operation of chain survey can be divided into three major groups namely, field work, keeping of records in the field book and plotting of data to prepare maps.
Field work in Chain surveying: In includes reconnaissance. Selection of the station, measurement of lines and taking offsets of different objects in the field. Reconnaissance: This is the preliminary survey in which to the survey party will examine the plot to be surveyed in order to know as to how the works can be executed in the best possible ways. The party will note all details like roads, buildings, canals, ditches, culverts and the difficulties and obstacles that may arise during the carrying out of the work.
The party should locate the suitable points for stations by driving pegs. Sometimes a small triangle or a circle is made around the stations and the pegs are inserted into the centers.
The party should then make a rough sketch of the plot showing the possible stations and from there the arrangement of different lines. It is important to give a north line on the rough sketch and though the sketch is not prepared according to the scale, it should represent the approximate positions of the different things in the plot and hence to be a good guide for further work.
Stations: These are points on the ground fixed by driving pegs. Every station should be located with respect to three permanent objects i. The advantage of taking this measurement is that if in future the peg at the station is lost, then it can be located again by knowing descriptions and distances of these objects.
The selection of a particular station depends upon the fallowing important considerations: The triangle should be a well-defined one, i. Every main station should be visible from the other two There should be a minimum number of obstacles in Ranging and chaining The chain line should run near the boundary of the plot The chain line should be as few as possible The chain line should be over an approximately leveled ground In the case of chaining along the road, it is always better to run chains on one side of the road to avoid interruptions by vehicles.
It is better not to cross the road frequently Offsets should not exceed one chain Check and tie lines should be provided in sufficient number so that all the main lines, of sets and other details, can be checked thoroughly Tie lines and check lines: A tie line is one which connects two points on the two main lines of the triangle. It helps in taking offsets of the objects falling within the triangle and which are too far away from the main line.
A checking line is also a tie line which helps in checking the accuracy of the work after plotting in a drawing sheet. A checking line or tie line is never extended beyond the main lines. Measurement of lines and taking offsets: In Fig the main station A is located with respect to three permanent objects and a ranging rod is fixed to the station. The three rods will be in a straight line when only the intermediate rod is visible if a man looks from A to B. Now measurement of line AB is taken by the chain.
The chain should be properly stretched so that there is no sag in it. In this way, all the lines including tie and check lines are measured and offset taken and recorded in the field book. Advantages and disadvantages of chain Surveying: This type of survey work is suited for a small plain ground It requires simple instruments Plotting of maps is very simple and easy But this type of surveying is not suitable for undulation land where chaining operation is tedious and subject to errors.
This method is not generally recommended for a crowded city with a large number of buildings and obstacles because it cannot be divided.
In the case of route surveying. These obstacles can be avoided in chaining operation by applying some fundamental geometric rules.
Drawing a perpendicular from a point on the chain line: AC is taken 4 units on the chain line XY. But AC is not a traverse because it does not meet in a cone 2 Types of Traverse: i. Open Traverse ii. Then it will be a closed traverse. In chain and tape survey closed traverse is usually done in small areas. Figure 2: Open and Closed Traverse 2.
BO will also act as an arm for OAB. It is not a good practice to measure common arm for different triangles, because an error is carried forward cumulatively. The chain is divided into links, marked off into groups of 10 by brass rings which simplify intermediate measurement.
Each link is 7. The full length of the chain is 66 feet. Gunter's chain reconciled two seemingly incompatible systems: the traditional English land measurements, based on the number 4, and the newly introduced system of decimals based on the number Since an acre measured 10 square chains in Gunter's system, the entire process of land measurement could be computed in decimalized chains and links, and then converted to acres by dividing the results by Each link is 1 ft in a length.
Used in all Engineering surveys. It should be noted here that the first, second, third, fourth and tally from either end of these chains indicate 10, 20, 30, 40 and 50 links respectively. Strands bronze- brass- copper wire woven in the warped face of the tape and coated with a tough plastic for 5 durability. Standard lengths are 50 and ft. Some are graduated in feet and inches to the nearest one-fourth in. Others are graduated in feet and decimals of a foot to the nearest 0.
Metallic tapes are generally used for rough measurements, such as cross-sectional work, road- work slope staking, side shots in topographic surveys, and many others in the same category. Nonmetallic tapes woven from synthetic yarn, such as nylon, and coated with plastic are available; some surveyors prefer to use tapes of this type.
Nonmetallic tapes are of special value to power and utility field personnel, especially when they are working in the vicinity of high- voltage circuits. The trough compass is used for finding magnetic north direction on the ground. They are also used to mark points which must be seen from a distance, in which case a flag may be attached to improve the visibility.
Ranging rods are straight round stalks, 3 to 4 cm thick and about 2 m long.