What is the hierarchy of positioning sources based on accuracy?

The hierarchy of positioning sources based on accuracy emphasizes the increasing precision provided by various navigation technologies. The correct sequence begins with Differential GPS (DGPS), which offers enhanced accuracy by correcting GPS signals using ground-based reference stations. This makes DGPS superior to the standard Positioning Service provided by GPS Precise Positioning Service (GPS PPS), which, while more accurate than Standard Positioning Service (GPS SPS), does not typically reach the precision level of DGPS due to the lack of corrections for signal errors.

Following DGPS in the hierarchy is GPS SPS, which provides a standard level of accuracy that is generally sufficient for many applications but is less precise than its differential counterpart or the specialized capabilities of GPS PPS. Finally, visual aids and radar, while useful for navigation, generally do not provide the same level of accuracy as the GPS-based systems, especially in poor visibility conditions.

This ordered approach reflects the variations in accuracy offered by different positioning sources, allowing navigators to select appropriate technologies based on their specific needs and circumstances. Each source's reliability and precision inform how navigators assess their positioning data, leading to safer and more effective navigation practices.