FP2VF: Fortran 90 program to generate a vector field from flowpaths

Many directional properties vary spatially and are related to geologic or other variables (e.g., deposition and erosion controlled by direction of flow in river systems). A vector field is a set of spatially distributed directions that are in the form of an array that contains an azimuth at every node. Vector fields are powerful tools, but generating them manually can be difficult: A flowpath, typically taken from a map, is defined to be a set of connected line segments that indicates the general direction of flow in the area of interest; flowpaths are more easily obtained than vector fields. Program FP2VF uses flowpaths to create a vector field based on the concept that the azimuth at a node should be similar to the orientations of nearby flowpaths. The program calculates an azimuth vector for every node in the array. This paper describes the program, its algorithm, and operating requirements.