GPS World - May 2008 - (Page 28)

BUSINESS OUTLOOK | Agriculture RTK Crops Up in Precision Ag M By Eric Gakstatter ost precision agriculture users have settled for 1-meter accuracy using GPS, made possible with the reliable and convenient corrections provided by WAAS (Wide Area Augmentation System). GPS/GNSS is important to key areas in agriculture, including field mapping, yield mapping, and guidance. Companies such as Hemisphere GPS (formerly CSI Wireless) did very well designing single-frequency GPS receivers for the precision ag market. Hemisphere is also a leading designer of radio beacon (Coast Guard) receivers. Radio beacons, in addition to WAAS, are a free source of corrections for 1-meter accuracy. Trimble was also an early supplier of precision ag GPS receivers and related equipment, offering single-frequency products such as the AG-132. While the real-time kinematic (RTK) technique has been around since the early ' 90s, it didn' t gain wide acceptance in the precision ag industry. The accuracy was great, down to approximately 2 centimeters at the time, but the equipment was clunky. The user had to set up a reference station near the field he was working on. The communication link was complicated, and some types needed Federal Communications Commission (FCC) licensing. Consequently, there were several potential points of failure. Lastly, the cost for a complete RTK system (base, rover, and radios) was upwards of $50,000. It just wasn' t cost-effective. The term RTK network is ambiguous because it means different things depending on the industry. Essentially, the hardware setup is the same no matter the industry. An RTK network is a series of dual-frequency reference stations spaced optimally within a region to provide RTK corrections to subscribers in that region. The network subscriber is assigned a primary reference station. RTK networks for agriculture are single-baseline solutions; the subscriber can only use one reference station at a time. There is no ª network solutionº or redundancy like there is in RTK networks used in the surveying and construction industries. Therefore, when a single reference station goes down, the subscribers in that area are down also. Another major difference between RTK networks for agriculture and RTK networks for surveying and construction is the communication method. The latter primarily use data plans on mobile phones to receive corrections. Either the mobile phone is linked via Bluetooth to the receiver or a cellular modem is built inside the receiver. RTK networks for agriculture, on the other hand, primarily use spread spectrum radios (900 Mhz band) to transmit corrections to the receiver. Spread spectrum radios are free to use and don' t require a license from the FCC to operate. They are limited in their broadcast range, however, typically to two to three miles. To solve this problem, radio repeaters are used to extend the distance. GPS World | May 2008 The Wild, Wild West Bill Henning, real-time specialist with the National Geodetic Survey (NGS), said it best: the recent explosion of RTK networks is like the wild, wild West. They are proliferating so quickly that it' s hard to keep track of them. One of his tasks is to help develop guidelines for RTK network operators, and I think NGS is making inroads into the survey/construction industry with its initiative. People are looking for guidance with respect to RTK network setup, as well as monitoring for the networks once they become operational. RTK networks for agriculture seem less structured than in other disciplines, though, and administrators rely more heavily on vendor recommendations. For example, some are based on the ITRF reference frame, while others are based on some version of NAD83. Some networks hire land surveyors to establish their reference station locations, while others do it themselves using NGS' s OPUS program or other methods. Very few, I think, realize the resources available from the NGS, such as the Cooperative CORS program. One would think that ag and survey/construction would consolidate their efforts, since an RTK network can cover the same area for both fields, and the equipment is virtually the same. But a farmer isn' t going to pay the same RTK network subscription rate that a surveyor or construction company will. A farmer is hesitant to pay $4,500 annually when he can select a service such as OmniSTAR and pay $1,500 annually. Some industry folks say that aggressive subscription pricing is the reason RTK networks in the agriculture market have expanded rapidly in the past few years. The differences between the networks used in agriculture and those in survey/construction are mostly software related. RTK networks for survey/construction offer a true-networked solution, where several reference stations are used to compute a correction, compared to the single-baseline solutions used in ag. OmniSTAR (HP/XP), John Deere (Starfire), and Novariant (AutoFarm) offer GPS-based solutions for precision ag. They are not pure-play RTK solutions like RTK networks, but they do have RTK capability. True RTK networks are capable of constantly delivering ~2-centimeter accuracy day in and day out. These companies going after the precision ag market offer primarily decimeter-level services (1 decimeter being the equivalent of 10 centimeters), and then RTK solutions when needed. It will be interesting to see how pure-play RTK players respond as RTK networks for agriculture continue to expand Ð which they most certainly will. 28 www.gpsworld.com http://www.gpsworld.com

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GPS World - May 2008 Contents Out in Front Letters to the Editor Expert Advice GPS III Contract Award Now a Reality? Near-Space Location Boost RTK Crops Up in Precision Ag Safety Afoot 50+ Leaders to Watch Making a Difference with GPS Product Showcase Advertisers Index & Company Directory Marketplace Classifieds Seen & Heard

GPS World - May 2008

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