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.

• 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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