Low cost high tech crop scouting with handheld GPS
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
in handheld global positioning system (GPS) receivers provide growers
with a low cost tool for crop scouting. A satellite based augmentation
system has been developed by the government for the aviation industry to
improve the accuracy and integrity of information signals broadcast by
GPS satellites. This technology is driving down the price and increasing
the accuracy of handheld GPS receivers. The primary commercial market
for these low cost handheld units is for travel and recreational
navigation. However, the technology has many practical applications in
Global positioning systems are not new to agriculture. In fact, they are custom equipment on most combines and large tractors. To achieve the level of precision needed for most agricultural applications, these units typically relied on land-based differential correction signals in addition to the GPS satellite signals. These land-based correction signals are available from several sources including the U.S. Coast Guard beacons, and pay-to-use subscription services. The correction signal, antennae requirements, and correction factor software contributed to the relatively high price of these GPS units.
The U.S. Federal Aviation Administration and Department of Transportation developed a satellite-based correction system called WAAS for “wide area augmentation system.” WAAS uses a system of approximately 25 ground-based reference stations, which monitor GPS satellite data. Two primary stations located on each coast, receive data from the reference stations and calculate a GPS correction signal, which accounts for GPS satellite signal errors from ionospheric disturbances, timing and satellite orbit errors. The correction signal is then broadcast through one of two satellites with a fixed orbit over the equator. The correction signal is compatible with the basic GPS signal structure and is able to be picked up free of charge by any WAAS enabled receiver. Initial WAAS testing, confirmed performance accuracy of three to six feet horizontal and six to nine feet vertical throughout the majority of the continental United States. Handheld GPS units equipped to use the WAAS signal are currently commercially available in the $200 range and are available at most sporting goods and outfitting stores.
How can these handheld GPS units be used in crop scouting? Many applications are possible, and given farmer ingenuity, many new uses will likely evolve over the next few years. The devices can be used to accurately identify the location of insect, disease, weed, nutrient, pH, tile blow-outs and other soil problems in the field observed while scouting. Once the problem areas are marked and electronically stored in the device’s memory, the unit can be used to navigate back to them later on for corrective action. The ability to navigate back to identified trouble spots makes this technology ideal for monitoring the effectiveness of applied treatments, whether they be pesticides, fertilizers or pH adjustments. In addition to marking and navigating, many of these handheld units have the capability to measure distances and even calculate acreage. Since the units measure elevation in addition to lateral position, they can also be used to determine surface drainage patterns. Most units also have a limited memory, which can be used to store shape-files of fields. The possibilities are endless, but perhaps best of all, once the field work is done, you can use the same unit to mark and navigate to your favorite fishing and hunting hotspots.