Position, Heading, Timing, Dead Reckoning...

Lost? Use the clue

Of course, you can make a good universal receiver. But it will be an expensive "camel" (a horse made by a committee). As a rule, more specialized options are made based on a single base by making small changes to the hardware and firmware.

Position. The most standard option for outputting coordinates. They come in standard and high accuracy (RTK, PPP), single-frequency and dual-frequency. Example - u-blox ZED-F9P.

Heading: This is used as part of a satellite compass. That is, we place two receivers on a vehicle or vessel and measure the direction from one to the other. As a result, we get the course, roll, or differential depending on the position of the antennas. With three receivers, you can measure the course, roll, and differential. In this configuration, one receiver (base) must be F9P, while the others (rovers) should be F9H. It's better because the F9H firmware is designed for working with a moving base, while the F9P firmware in rover mode is designed for a stationary base. On the other hand, the F9H has fewer features, making it cheaper.

Timing: A receiver for providing accurate time and frequency signals. Let's specifically look at an example with the same chipset - u-blox ZED-F9T and compare it with the base version - F9P. We immediately see that there are two signals instead of one, the frequency range has increased from 10 MHz to 25 MHz, and the standard deviation has improved from 30 ns to 5 ns (or 2.5 ns in differential mode). The most important thing is the jitter. In a regular receiver, the 1PPS system operates at a frequency of about 16 MHz, giving a jitter of ±30 ns, while in the F9T, it operates at 125 MHz, giving a jitter of ±4 ns. This is a real hardware modification, not just marketing tricks. On the other hand, this receiver is much worse for outputting coordinates, its autonomous mode horizontal accuracy is 2 meters CEP50 instead of 1.5 meters for F9P, and the RTK mode for coordinates is either absent or not standardized.

Dead Reckoning: This allows for temporary operation in areas where there is no GNSS reception, such as tunnels. These receivers have built-in gyroscopes and accelerometers, meaning they are capable of not only satellite navigation but also inertial navigation (INS). Moreover, thanks to the INS, such a receiver can provide solutions more frequently than GNSS, making it suitable for fast processes like autonomous vehicle guidance and drones. There are two types: ADR and UDR. It's clear that such a receiver has additional hardware that makes it more expensive.

ADR - Automotive Dead Reckoning: In addition to INS, a high-speed odometer is used, i.e., signals from wheel rotation sensors. This is a car system.

UDR - Untethered Dead Reckoning: This is a system without an odometer, used for drones and ships. 

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