There are numerous algorithms that calculate the roots of single-variable nonlinear functions. The most popular of such algorithms is Newton's method. The slowest and simplest root seeking algorithm is the Bisection method. This method has the user select an interval that contains the sought root. The method iteratively shrinks the root-bracketing interval to zoom in on the sought root.

PDQ finds best rational approximations, with infinite precision. This means it finds the two smallest integers whose ratio is equal to some target real number plus or minus some desired tolerance. In other words, it finds the simplest fraction in any given interval. Unlike other methods, it always finds the unique best answer, and uses the infinite precision of CAS long integers.

Creates a list with station and elevation information in L0. If a value between the VPC and VPT is entered in "Special Station", it returns data for that station only, if left at 0 the entire curve will be returned at the interval specified.