Method for inversion of corresponding line mileage and offset by using known coordinate point

A method for inversion of a path mileage and offset by using a known coordinate point, comprising: based on coordinates of a known point P and curve elements of a start location and an end location of a curve element, first segmenting or not segmenting the curve element according to a corner of the curve element to obtain a plurality of curve sub-elements (AiBi), and calculating curve elements of the curve sub-elements (AiBi); taking any curve sub-element (AiBi) to calculate a half chord length S and a straight corner θ, and performing precision determination and convergence correction according to S and θ, the point P being always effective with respect to the curve sub-element (AiBi) in the correction process; and performing cyclic convergence calculation to finally obtain a distance from the point P to any point on a chord line or an arc line as an offset of the curve sub-element (AiBi) corresponding to the point P and to obtain a mileage of the curve sub-element (AiBi) corresponding to the point P. By calculating different curve sub-elements (AiBi), an effective offset and an effective mileage of the curve sub-element (AiBi) corresponding to the point P can be finally obtained. The method is suitable for mileage inversion of curve elements which comprise a large-corner curve element, the calculation process is always converged, the situation that calculation cannot be performed is avoided, and the calculation process is relatively simple.