Precision Agriculture and GPS FAQ's
What is Precision Agriculture?
Precision Agriculture is the application of information technologies, specifically Variable Rate Application, GPS and GIS to the management of farms. The goal of Precision Agriculture is to improve efficiency and improve the quality and consistency agricultural products.
What is GPS and How Does it Work?
You may have heard how the use of GPS is revolutionizing the agriculture industry, from finding your way to the middle of a corn field and accurate field guidance without foam markers, to critical row-crop driving and precise elevation mapping. But what is it? Use the Trimble GPS tutorial to learn how GPS works and how people are using it.
How is GPS used in Agriculture?
GPS receivers use signals from four or more satellites to compute the user’s position, velocity, time, and other data as needed for precision agricultural applications. This data is collected on memory cards along with yield data for use in the office by an agricultural software package. Other agricultural applications of GPS include field mapping, controlling the application of agricultural chemicals, crop scouting, variable rate planting and parallel swath guidance.
How accurate is GPS?
Depending on the design of the GPS receiver and the measurement techniques employed, the accuracy range is from 100 meters to better than 1 centimeter. Many mapping applications use GPS receivers with sub-meter accuracy. In order to obtain better than 100 meter accuracy, differential GPS must be used.
What is Differential GPS(DGPS)?
Differential GPS is used for mapping applications to overcome the effects of SA and atmospheric signal distortions. Depending on the technique and the kind of GPS receivers used, differential GPS can provide a position accuracy of about 10 meters to better than 1 centimeter, and speed accuracy of better than 0.1 mph. Differential GPS corrections are available for both real-time and post-processed applications from a variety of public and commercial sources which will meet the requirements of many mapping users.
What does Repeatability mean?
Repeatability is a term often used in precision agriculture today. This is generally understood to mean the ability of a GPS receiver or GPS guidance system to bring you back to the exact same spot in the field reliably each time you drive into the field, from year to year. Whether absolutely accurate or relatively accurate, agricultural guidance applications often demand good system repeatability. RTK or Real Time Kinematic GPS receivers with centimeter static accuracy are the best at providing high repeatability in an agricultural field. For example, the ability to come back into a field and place seed on top of a fertilizer strip in strip till; the ability to cultivate between crop rows; the ability to avoid ripping up drip tape during tillage between crops.
What are the main features that separate one GPS receiver from another?
There are two kinds of capabilities of GPS receivers: the capability of the GPS engine and the capabilities of the user application software. The differences between GPS engines are sometimes described by the following parameters: time-to-first-fix, number of fixes per second, differential position accuracy, differential speed accuracy, and power consumption. Differences in GPS engine parameters result from a trade-off in the engineering design phase regarding cost and performance, and have measurable effects on the GPS engine performance. Price and performance are related: the lower cost GPS receivers usually have lower performance than more expensive GPS receivers. The difference between the user application software of GPS receivers results in one GPS receiver being well suited for a particular application and another GPS receiver incapable of performing in the same application.
What is the effect of thunderstorms on the GPS signal?
There are a number of possible effects of thunderstorms on the GPS signals and GPS receivers. The largest effect is caused by a direct or near-miss lightning strike, which could permanently damage the GPS receiver. To protect GPS receivers in fixed, base station installations, lightning protection is recommended. The second possible effect of lightning is from the electromagnetic noise generated by the multitude of lightning strikes in a nearby (or maybe not so nearby if it is severe enough) thunder storm interfering with the differential GPS radio link. Using a magnetic loop antenna on the beacon receiver will somewhat reduce the effect of local lightning interference. The medium frequency beacon signals are subject to this kind of interference while there is almost no effect on the GPS or satellite differential signals unless the lightning strikes are very close.
Can GPS be used in the rain or in snow or sleet?
Rain, sleet or snow in the air between the GPS antenna and a satellite will normally have no measurable effect on the GPS signal. Snow or ice, however, may pile up on a GPS antenna and absorb some of the GPS signal reaching the GPS antenna.
Why should I buy Trimble GPS equipment?
Quality, performance, reliability, service and support are all part of the Trimble tradition. Trimble Navigation has been involved in Differential GPS applications from the beginning and is a supplier of DGPS receivers to the U. S. Coast Guard, where they are used in conjunction with the U. S. Coast Guard beacon differential GPS transmissions, one of the main sources of differential GPS. In addition, many manufacturers have recognized the superiority of Trimble GPS technology and have chosen to integrate Trimble GPS boards into their products. With the Trimble AgGPS 122 and 132 you can own the highest performance DGPS receiver available for agricultural applications.