1. A system for detecting a boundary crossing event, the system comprising: a memory; and a processor configured by the memory to perform the steps of: sensing current position; comparing the sensed current position to model zone data to determine presence within a geometric figure constructed around a boundary crossing point; comparing the sensed current position to model subzone data to determine presence within a first portion of the geometric figure; comparing the sensed current position to model subzone data to determine presence within a second portion of the geometric figure; and detecting a boundary crossing event as a result of movement from the first portion of the geometric figure to the second portion of the geometric figure.