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In order to make an intelligent decision in selecting or using a GPS system, there are certain fundamentals that need to be understood. We will attempt present some of those here.
Single Frequency vs. Dual Frequency
GPS today is founded primarily on a "constellation" of satellites, known as Navstar, that is maintained by the United States. These satellites broadcast information on two different frequencies that are called L1 and L2. Single frequency receivers receive only the L1 frequency whereas dual frequency receivers receiver both L1 and L2.
Single frequency receivers are just as accurate as dual frequency receivers at distances less than about 6 miles. This is because the L1 frequency inherently can provide higher accuracy so, when processing the data, the L2 frequency is eventually thrown away when the processing software gets close enough to the solution. The second frequency helps the processing software find a solution faster but, in the end, the solution is calculated from the L1 data alone.
Dual frequency receivers require less time to find a solution due to the fact that they are getting twice as much information in a given data sample as a single frequency receiver. Occupation or "sit times" with a single frequency receiver are typically on the order of 20 minutes whereas dual frequency uses typically 10 minutes.
Dual frequency receivers can be used on baselines extending to 25 miles and more whereas single frequency receivers are limited to about 6 miles when trying to obtain survey-grade (centimeter) accuracy. This is because the two frequencies can be used mathematically to correct for errors that occur as a result of the satellite signals passing through the ionosphere.
Perhaps the biggest advantage of dual-frequency receivers over single-frequency receivers is their ability to recover after losing a "lock" on the satellites when being used in a kinematic mode (more on this later).
Dual frequency receivers are MUCH more expensive than single frequency receivers. Single frequency receiver boards typically cost a few hundred dollars. Dual frequency receiver boards cost several thousand dollars. That is "an order of magnitude" and results from the fact that the L2 frequency is encrypted and the algorithms that are used to get useful information from the L2 frequency are highly proprietary and costly to develop.
A good uses of single frequency receivers is in setting control. Dual frequency's main claim to fame is its ability to provide useful real time positioning.
Static vs. Kinematic
"Static" and "Kinematic" refer to different methods of collecting GPS data. This has nothing to do with the hardware - it is a procedural thing.
Static - The receivers don't move while collecting.
Kinematic - The base receiver remains stationary, but the "rover" receiver (the one you're holding) is moving during collection.
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