Civil Engineering - Surveying - Discussion

If the radius of a simple curve is R, the length of the chord for calculating offsets by the method of chords produced, should not exceed R/20.

L = r/20.

Chord length for curve setting is derived from the formula of errors. The greater chord length we take, the greater be the chances of error in measurement because while using the method 'OFFSET FROM CHORD PRODUCED' we take the chord distances whereas we consider them as straight lines. You will see while taking the first chord in the method, we mention that Chord length~arc length. Now, if we use R/10, the error is 1 in 2500, which is pretty significant. But if we use R/20, the error is 1 in 10, 10000 which is considerably low and cannot be seen or detected from a human perspective. Hence R/20 is the correct value.

R/20 is absolutely right.

Anyone can explain?

@Dev.

Length = r/20 = 600/20 = 30.

Please explain the formula clearly.

Well said @Roshika.

Nice explanation. Thanks.

Please derive the formula R/20.