Data Collection Mapping and Consulting Precision Agriculture Real Estate Crop Insurance

GPS DATA COLLECTION
A cornerstone of any Precision Agriculture program or Geographic Information System is the collection of data. Whether you are measuring shapes, lines, or points, the following three factors are of utmost importance:
  • The measurements must be taken with an appropriate degree of accuracy.
  • The data must be flexible so that it can be used in a number of applications, manipulated, and updated.
  • It must be collected with low impact on the land and crops.
Harvest GeoGraphics has the people and the equipment to tailor GPS data collection to meet your needs. In order to fully understand the type of collection you will need, it is important to be familiar with the concepts of the Global Positioning System (GPS), and Differential Correction (DGPS).

What is Global Positioning System (GPS):

  • Developed by the Department of Defense at a cost of $12 billion
  • A system of 24 Rockwell Navstar satellites orbiting at 10,900 nautical miles as well as five ground control stations
  • Satellites send a signal to a roving receiver
  • Triangulate ground position based on the distance from at least four satellites
  • Accuracy with this system alone is 10 to 15 meters
  • Errors are based on atmospheric conditions, small changes in satellite position, timing errors, etc.
  • This technology is typically used in "recreational grade" receivers costing a few hundred dollars

What is Differential Correction (DGPS):

  • Combines the GPS satellite signal with a signal from a second source, either satellite or ground-based beacons
  • The second source calculates the current position of the satellite, and the "correct" position of the satellite, then it takes the difference between the two positions to find the correction factor
  • The second source continuously sends this correction information to the roving receiver, which can then correct its measurements.
  • Beacon Systems include Coast Guard Beacons at Appleton, WA, Fort Stevens, OR, and various other sights around the Northwest
  • Satellite Systems include Omnistar
  • Accuracy of this system is much greater, because much of the error in the GPS system alone is eliminated leading to sub-meter accuracy
  • This technology is typically used in "resource" or "mapping" grade receivers costing several thousand dollars


Harvest GeoGraphics utilizes Trimble® GPS Navigation products. The first unit is a Pathfinder Pro XRS. This receiver uses a minimum of four GPS Satellites, and either beacon or satellite differential corrections in calculating its position. The Pro XRS specifications indicate an accuracy of within 50 centimeters.


The Pathfinder Pro XRS is equipped with the TSC-1® data collector shown above. This collector allows for easy two-way communication flow between the receiver and a workstation. It makes it possible to collect and attribute large amounts of data very efficiently. The TSC-1® also allows for real-time display of differentially corrected GPS data. This means that the operator can navigate to predetermined points to update data, or view a real-time display of the data they are currently collecting.

The other two GPS receivers are Trimble® Ag132's with either beacon or satellite differential corrections. These receivers also have accuracy specifications of within 50 centimeters.

In addition to the above units we have added RTK GPS capability for Very High Accuracy GPS applications. (Added 11/3/06)

In the end, the most important part of any GPS data collection project is the people involved. At Harvest GeoGraphics we have practical experience operating the equipment described above. Not only will they complete the project with the data you need, you can be sure that they will take great care to collect the data with minimal impact to the crops or the land.