FIVE KEY CONCEPTS

March 23, 2023  - By
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GNSS integrity is key to precision agriculture. (Image: fotokostic/iStock/Getty Images Plus/Getty Images)

 

In the world of global navigation satellite systems (GNSS), there are five key watchwords: accuracy, integrity, availability, continuity and coverage. While all five of those parameters are very important, their priority order depends on the application.

Accuracy: how well a measured or estimated position or time conforms with its true value. If you are a surveyor, accuracy and integrity are your biggest concerns. Accuracy is not to be confused with precision, which is a measure of exactness. It can refer to the number of significant digits reported for a measurement, the rigor of the measuring process, or the agreement among repeated measurements. For example, for locational error a measurement of 9.725m is more precise than 9.7m but may not be a more accurate measure of the error. A measuring instrument is precise if it repeatedly gives similar measurements, regardless of whether these are actually accurate. They could all be off by, say, 5m, due to some bias in the measurement process. In short, precise data may be inaccurate and accurate data may be imprecise.

Integrity: how much the information supplied by the system can be trusted to be correct. This requires the system to provide timely warnings to the user when the equipment is unreliable for navigation purposes—due to obstructions, jamming, multipath or any other event that degrades accuracy.

Availability: the percentage of time that a signal is available to the user. For location-based services, this and coverage are probably the most important parameters.

Continuity: the ability of the total navigation system to continue to perform its function during the intended operation. Continuity is critical whenever reliance on a particular system is high. For a pilot during an instrument approach procedure, continuity and integrity are vital.

Coverage: the area over which a signal is required. For farmers, it is their fields, for ships, the world’s oceans.

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About the Author: Matteo Luccio

Matteo Luccio, GPS World’s Editor-in-Chief, possesses more than 20 years of experience as a writer and editor for GNSS and geospatial technology magazines. He began his career in the industry in 2000, serving as managing editor of GPS World and Galileo’s World, then as editor of Earth Observation Magazine and GIS Monitor. His technical articles have been published in more than 20 professional magazines, including Professional Surveyor Magazine, Apogeo Spatial and xyHt. Luccio holds a master’s degree in political science from MIT. He can be reached at mluccio@northcoastmedia.net or 541-543-0525.