Jacob Farms has used Global Positioning Systems (GPS) on our tractors, sprayers, and combines since 2005. There are different levels of accuracy with satellite navigation, and the highest level is called RTK, or Real-Time Kinetic satellite navigation. RTK features sub-inch accuracy pass to pass.
Since going to this level of automatic guidance, we have seen many improvements in yields, reduction of inputs, and increased efficiencies. Having auto-steer also allows the driver to be much less fatigued at the end of the day and spend his time monitoring the planter more closely instead of driving.
In combination with this technology, we also implemented auto row and nozzle shut-off, which allows the planter or sprayer to quit planting seed or applying fertilizer once it crosses into an area previously planted or fertilized. With the high cost of fertilizer and seed, this saves us and our land-owners a substantial amount of money over the planting season by eliminating overlap. Another benefit of satellite guidance is having controlled traffic in the field, which helps to control compaction caused by multiple trips over the field.