GPS Receiver Demonstrates Accuracies with and without Differential Correction

Mark Morgan and Viacheslav I. Adamchuk November 2000

Most people associate precision farming or site-specific management with

the global positioning system (GPS). GPS's primary goal is to locate the

antenna of a GPS receiver in global coordinates that represent the Earth.

This gives one the opportunity to record a set of geographic coordinates

that specify particular locations within the field. Data collected using

GPS technology is commonly referred to as "georeferenced". Processing of

these data is not trivial. Software packages designed for precision

farming applications have built-in capabilities to interpret GPS receiver

output. However, some simple operations could be performed using standard

office software. In this case, it is necessary to know basics behind GPS

data and different coordinate systems.

Has been developed to illustrate georeferenced data processing techniques

assisting in understanding the main principles of spatial data. Although

complex to derive, simple equations in a regular spreadsheet program can

be used to convert Latitude/longitude coordinates into units of Feet or

Meters. This website also illustrates one method to obtain a field

boundary, map yield or soil properties, and compare soil and yield data

using a spreadsheet.

illustrate variations in GPS position data obtained by a receiver whose

antenna is located on the roof of the ABE building (Purdue University,

West Lafayette, IN). Position is recorded continuously every 5 minutes.

Some days the positions were recorded without differential corrections and

others have differential correction from the coast guard beacon.