How to Choose GPS/GNSS Accuracy

Kurt LawtonGPS, Guidance, Satellite, University

If you’re just starting to look at more advanced precision agriculture practices on your farm such as auto steer, take a look at your operation to see which signal is right for you. Jonathan Hall, a grad assistant at Auburn University, offers some tips on the Precision Ag Blog.

After exploring all of the equipment that can be purchased, you will find that there are three basic options for GPS accuracy:

1. A free signal, known as Wide Area Augmentation System (WAAS), provides pass-to-pass accuracy of about ±6 to 13 inches and has a potential GPS drift of ±4 to ±7 ft. WAAS is managed by the Federal Aviation Administration (FAA).

2. A “corrected” signal that requires a paid subscription can provide a pass-to-pass accuracy between ±2 and ±13 inches and has a potential GPS drift of ±1.7 to ±3 ft depending on the correction service.

3. A real-time kinematic (RTK) system that provides pass-to-pass accuracy of ±1 inch and a potential GPS drift of ±1 inch. This system requires the purchase of an RTK base station if an RTK network, such as CORS, does not already exist in your area. The Continually Operation Reference Station (CORS) network is a free RTK signal operated and monitored by the National Geodetic Survey (NGS). If CORS is not available in your area an annual subscription for a proprietary RTK network can be purchased.

It is important to keep in mind two terms relating to GPS/GNSS accuracy when evaluating signal options. Pass-to-pass accuracy is the accuracy of the GPS/GNSS receiver over a 15 minute time-frame and pertains to short-term operations such as spraying or fertilizing fields. GPS drift is the accuracy of the GPS/GNSS receiver over an extended period of time. GPS drift is more long-term and becomes important when planting or harvesting.

Check out his piece to learn more.