Precision Farming. Modern agricultural management practices are changing from assuming homogenous fields to attempting to address field variability by dividing the field into smaller zones and managing these zones separately. Precision farming can be defined as the gathering of information dealing with spatial and temporal variation within a field and then using that information to manage inputs and practices (Precision Farming: A Comprehensive Approach, Virginia Cooperative Extension (VCE) publication 442-500). Precision farming is made possible by linking computers, on-the-go sensors, Global Positioning Systems (GPS), and other devices. This publication discusses GPS principles and the technology that makes it possible.