Chainage of Simple Curve Starting Point

This problem asks us to find the chainage of the starting point of a simple curve, given the tangent length and the chainage of the point of intersection.

In highway or railway surveying, when designing curves, several points are important:

• Point of Intersection (PI): The point where the two tangent lines intersect if the curve were not present.
• Starting Point of Curve (PC): Also known as the Point of Commencement or Tangent-Curve (TC). This is where the curve begins.
• End Point of Curve (PT): Also known as the Point of Tangency or Curve-Tangent (CT). This is where the curve ends and transitions back to a tangent.

The tangent length is the distance along the tangent from the Point of Intersection (PI) to the Starting Point of Curve (PC), or from the Point of Intersection (PI) to the End Point of Curve (PT). For a simple curve, these two tangent lengths are equal.

The chainage is the cumulative distance measured along the center line from a starting reference point.

To find the chainage of the Starting Point of Curve (PC), we need to subtract the tangent length from the chainage of the Point of Intersection (PI), because the PC is located before the PI along the survey line.

The formula is:

\( \text{Chainage of PC} = \text{Chainage of PI} - \text{Tangent Length} \)

Given:

• Tangent Length = 10 m
• Chainage of Point of Intersection (PI) = 344.465 m

Now, we can substitute the given values into the formula:

\( \text{Chainage of PC} = 344.465 \text{ m} - 10 \text{ m} \)

Performing the subtraction:

\( \text{Chainage of PC} = 334.465 \text{ m} \)

Therefore, the chainage of the starting point of the curve is 334.465 m.