Why does the PI Station reported in geometry reports and horizontal annotation not match the station reported when using the horizontal tracking command?
This difference in the two values is a result of the method in which PI Station is calculated:
The intersection point of a horizontal curve is defined as the Point of Tangent Intersection (PI). The location of the curve's start point is defined as the Point of Curve (PC) while the location of the curve's end point is defined as the Point of Tangent (PT). Both the PC and PT are a distance "T" from the PI, where T is defined as Tangent Length.
By definition, PIstation = PCstation + T.
Because the PI station is calculated in this way and the horizontal tracking is calculated along the length of the curve, the two values will differ.