Saturday, September 7, 2013

Surveying - one line statements useful for GATE, PSUs examination preparations -Part 2

1. Theory of probability is applied to accidental errors.
2. Most probable value of an observed quantity available from a given set of observation is the one for which the sum of the square of errors is a minimum. This statement is called principle of least square.
3. For a measured distance L along a slope, the required slope correction is 2L.[sin(A/2)]^2.
4. A 30 m chain was found to be 20 cm too long after chaining 1500 m. Correct length of the total distance chained will be 1510 m.
5. If n observations are taken then the accidental errors are proportional to n^(1/2).
6. If a chain is found too short on testing then it can be adjusted by straightening the links, inserting additional circular links and flattening the circular rings.
7. Permissible limits of error in chaining for measurement on rough or hilly ground is 1:250
8. Position of point can be fixed more accurately by perpendicular offset.
9.  Positive error is caused if  length of chain is shorter than standard, slope and sag corrections in not applied and measurements are made along the incorrectly aligned line.
10. If during a chain survey along a straight line, leader of the survey party has three arrows and while follower has five arrows, then distance of the follower from the starting point is Five chains.

Reference: GK publishers

Solved Example-Distance of a Point from a Line, whose end Co-ordinates are given.

Hi, Problem: The X and Y co-ordinates(in meters) of station Shore are 246.87 and 659.46 respectively, and those for station Rock are 437...

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