### Surveying notes for GATE, PSUs - Part 8

Hello there,

How have you been? Here is 8th part of one liners for the preparation of the GATE and PSUs.

How have you been? Here is 8th part of one liners for the preparation of the GATE and PSUs.

- A curve tangential to four straight lines and consisting of arcs of different radii is known as
**three centred compound curve.** - The length of the tangent of a curve of radius R and angle of deflection D is given by
**R.tan(D/2).** - The length of the long chord of a simple circular curve of radius R and angle of deflection D is
**2R.sin(D/2).** - Setting out a curve by two Theodolite method does not require linear measurements.
- If r is the radius of curvature at any point of a transition curve and l is the distance from the beginning of the transition curve to that point, then for ideal transition l is inversely proportional to r.
- In a reverse curve, the super-elevation provided at the point of reverse curvature is zero.
- Total angle of deflection of a spiral curve is (spiral angle/4).
- The shape of vertical curve generally provided is parabolic.
- Perpendicular offset from the junction of transition curve and circular curve to the tangent is equal to four times the shift.
- If L is the length of transition curve and R is the radius of circular curve, then the shift of the curve is directly proportional to L^2 and inversely proportional to R.
- The difference in elevation of points between a vertical and a tangent is directly proportional to the square of its horizontal distance from the point of tangency.
- Shift bisects the transition curve and transition curve bisects the shift.
- The maximum value of centrifugal ratio on roads and railways respectively are 1/4 and 1/8.
- Agonic line is the line joining points having zero declination.
- For a circumpolar star, declination must be more than co-latitude.
- For a star at its upper transit, the local sidereal time is equal to R.A. of the star.
- Sidereal year(SY) is greater than Tropical year(TY).
- The limiting minimum value of declination of a circumpolar star having latitude 40 degrees North is (90-40) = 50 degrees.

All information is learned through books and practical exercises.

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