Chain surveying
TITLE: CHAIN MEASUREMENT)
TRAINGULATION
(LINEAR
OBJECTIVE: 1. To prepare overall sketch of the given plot and reference the traverse with sketch. Two way measurement of each traverse legs.(forward and backward) 2. To prepare detailing in chain traverse by linear offsets perpendicular, oblique, etc
INSTRUMENT: 1. Measuring tape 2. Ranging rods 3. Pegs 4. Arrows 5. Plum bob 6. chain
THEORY: Chaining: chaining is one of the method of land surveying. In this system various triangles are measured directly in the field and no angular measurements are taken. chaining is done to secure necessary data for exact description of the boundaries of a plot land, to determine the area of plot, to prepare an accurate plan of land, to divide a plot land into number of smaller units, etc. chaining is suitable when the ground is fairly level and open with simple details, when large scale plans are required such as for factory sites, when the area is comparatively small in extent. The principle of chain surveying is to divide the area into a number of triangles of suitable sides. As triangle is the only simple plane geometrical figure which can be plotted with its sides alone, a network of triangle is preferred to in chain surveying.
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Chain surveying
Principles of chain surveying: Field book: the book in which the chain or tape measurements are entered is called the field bppk. It is an oblong of size about 20cm*12cm and opens lengthwise. The main requirement of the field book are that it should contain good quality stout opaque paper, it should be welled bound and of size convenient for the pocket. The chain line may be represented either by a single line or by two lines spaced about 1.5cm or 2cm apart, ruled down the middle of each page.
Technical terms and their definitions: The important technical terms used in chain surveying are:
1. Main Survey Station: The point where two sides of a main triangle meet is called, a main survey station. Main survey station is a point at either end of a chain line. 2. Subsidiary Survey Station: The station which are selected on the main survey lines for running auxiliary lines, are called subsidiary station. 3. Main Survey Lines: The chain line joining the two main survey stations is known as the main survey lines. 4. Auxiliary, Subsidiary, or Tie Lines: The chain line joining the two subsidiary survey stations is known as subsidiary, auxiliary or more commonly as tie line. They are provided to locate the interior details which are far away from main lines. 5. Base Lines: The longest of the main survey lines, is called a base line. 6. Check Lines: The line which is run in the field to check the accuracy of the field work is called the check line. If the measured length of check line agrees with the length scaled off the plan, the survey is accurate.
PROCEDURE: 1. Select five survey stations A, B, C, D, and E such that from each survey station the other stations are visible in such way that each triangle formed are about well conditioned. 2. Select the longest line as base line and start to take tke forward and backward measurements measurements of each survey lines. 3. Fix the intermediate station points if required. 4. Measure the offsets either oblique or perpendicular to each of the objects and the building in or around the field to the t he nearest survey lines. 5. Take bearing of the base line. 6. Measure the check lines. 7. sketch the field books of each survey lines.
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Chain surveying
OBSERVATION AND CALCULATION: Table No: 2.1 Determination of precision Distance Forward Backward Mean Discrepancy Precision AB 37.711 37.713 37.712 0.002 1:18856 BC 25.536 25.536 25.536 0.000 1: ∞ CD 34.150 34.149 34.149 0.001 1:34000 DA 25.900 25.892 25.896 0.008 1:3200 AE 24.836 24.842 24.839 0.006 1:4100 BE 21.568 21.577 21.572 0.009 1:2400 CE 23.836 23.832 23.834 0.004 1:6000 DE 20.778 20.778 20.778 0.000 1: ∞
CONCLUSION: Hence we can draw the conclusion that by chain triangulation we can plot the overall sketch and field book of the lines and the detailed figure by help of linear offsets perpendicular and oblique etc.
DISCUSSION In this chain surveying we are known to the various types of surveying instruments used in chain surveying. We applied the principles of chain surveying for plotting the given field. However some errors occurred which were under the limit, the errors were mostly due to the wind, people, objects and the instruments. We became familiar to sketch the field book and known to draw the detailed figure of the plot in the scale.
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