Civil Engineering - Surveying - Discussion

Inside the Great Triangle:

If the plane table station lies inside the triangle formed by the three known points (referred to as the "great triangle"), the fix is generally good. The station is well within the bounds defined by the known points.

Outside the Great Triangle:

If the plane table station lies outside the triangle but not on the circumscribing circle, the fix is still acceptable, though potentially less accurate. The geometric relationship is weaker than if the station were inside the triangle.

On the Circumference of the Circumscribing Circle:
This condition is problematic because the station lies on the circle that passes through all three known points. In this case, the angles subtended by the lines joining the station to the known points can be ambiguous or lead to significant errors, resulting in a poor fix. This is known as the "danger circle" or "danger zone" in plane table surveying.

The correct answer should be 'B', cause when instrument point "nearer to the circumference" of great circle then fix is bad. And when it is "on the circumference" of the great triangle instrument point will be indeterminate.

We draw lines to the three points and draw circle joining these three points.

So if the station is on the circumference then it maybe difficult to calculate area and degree.

And it is 'good' if it lies in the great triangle.

Anyone, please explain this in detail.

Option A is the correct answer.

How it is determine?

Right Answer @Jawad.

Nice, Thanks @Jawad.

Thanks.