One objective of precision agriculture is to improve the accuracy of information about soil and crop properties to optimize the management of agricultural inputs according to economically-justified local need. This paper describes the development of a sensor equipped with RTK-GPS technology that continuously and efficiently measures soil compaction at various depths while traversing the field. Laboratory and field tests verified the accuracy of this prototype soil compaction sensor. A hand-operated soil cone penetrometer was compared to this field soil compaction depth profile sensor. To date, this sensor implement has only been tested in one field under one gravimetric water content condition. In this field examination, the relationships between the soil compaction profile sensor cutting force and soil cone index values are assumed to be quadratic for the various depths considered: 0–10, 10–20 and 20–30 cm (r2=0.58, 0.45 and 0.54, respectively). Soil resistance contour maps illustrated its practical value. The sensor provides accurate, timely and affordable information on soil properties to optimize resources and improve agricultural economics.