CHECK ON CLOSED AND OPEN TRAVERSE FOR COMPASS SURVEYING

CHECK ON CLOSED AND OPEN TRAVERSE

CHECK ON CLOSED TRAVERS

1). Check on angular measurements.

a). The sum of measured interior angles should be equal to (2n-4) x 90⁰ where  n is the number of sides of the traverse.

b). The sum of measured exterior angles should be equal to (2n+4) x 90⁰.

c). The algebraic sum of the deflection angles should be equal to 360⁰.

Right hand deflections are considered positive and left-hand deflection negative.

2). Check on linear measurements.

a). A line should be once each of two different days (along opposite direction). Both measurement should tally.

b). Linear measurements should also be taken by stadia method. The measurements by chaining or by other method should tally.

CHECK ON OPEN TRAVERS

In open traverse, the measurements can not be checked directly. But some field measurements can be taken to check the accuracy of the work. The methods are discussed below.

a). Taking cut-off lines. Cut-off lines are taken between some intermediate stations of the open traverse. Suppose ABCDEFG represents an open traverse. Let AD and DG be the cut-off lines. The length and the magnetic of the cut-off lines are measured accurately. After plotting the traverse, the distances and bearings are noted from the map. These distances and bearings should tally with the actual records obtained from the field (Fig. 12)

b). Taking an auxiliary point. Suppose ABCDEF an open traverse. A permanent point P is selected on the side of it. The magnetic bearings of this point are taken from traverse stations A, B, C, D, etc. If the survey carried out accurately and so is the plotting, all the measured bearings of P when plotted should meet at the point P. The permanent point P is known as the ‘auxiliary point (Fig. 13)

(Next Post on “PLANE TABLE SURVEYING”.)