GPS and its Application in Agriculture

GPS

It is a ''Global Positioning System'' which provides reasonably accurate coordinates to determine user's location on or near the earth's surface.

GPS is a satellite based navigation and surveying system for determining precise position and time using radio signals from satellite in real time or in real post processing mode.

GPS Elements:-

• Space segment

• Control segment

• User segment

Space Segment

• GPS satellites fly in circular orbits at an altitude of 20,200 km with a period of 12 hours.

• Powered by solar cells.

The satellite continuously orient themselves to point their solar panels toward the sun and their antenna toward the earth.

• Orbital planes are centered on earth.

• Orbits are designed so that, at least, six satellites are always within line of site from any location on the planet.

Control Segment

The CS consists of 3 entities:-

• Master Control System

• Monitor Stations

• Ground Antennas

User Segment

• GPS receivers are generally composed of :-

1. an antenna ( tuned to the frequencies transmitted by the satellites'

2. receiver-processors, and

3. highly-stable clock (commonly a crystal oscillator

• They can also include a display for showing location and speed information to the user.

• A receiver is often described by its number pf channels.

3. As of recent, receivers usually have between twelve and twenty channels.

Application of GPS in Agriculture:-

• GPS satellites broadcast signals that allows GPS receivers to calculate their position.

• This information is provided in real time, meaning that continues position information is provided while in motion.

• The uncorrected GPS signals must be compared to a land based or satellite based signals that provides position correction called differential correction.

• GPS applications in precision farming includes soil sample collection, chemical application, control and harvest yield monitors.

• When collecting soil samples, GPS is used to precisely locates the sample points from a predefined grid.

• Based on sprayer's location, system will apply chemicals at right spots with minimal overlap, and automatically adjust their rate.

• This, in addition to increase productivity, ensures that chemical and fuel are used efficiently.