adafruit/Adafruit_GPS

Сalculating velocity vectors by NMEA protocol

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brightproject commented

You could say that I am new to using GNSS and the NMEA protocol.
gps-nmea-0183_img01

There was a need to determine speeds in the cardinal directions and down or up.
The UBX protocol makes it possible to obtain such data

velN
velE
velD

NED_velocity
But in the NMEA data format I found the only mention of direction and speed, this is the $VTG parameter.
VTG_NMEA

But despite my little knowledge of the NMEA protocol, it seems to me that $VTG is simply a duplication of information from the $RMC.
That is, the $VTG sequence is redundant information of the $RMC sequence.
I could be wrong and actually I need to find a solution - how to get the speed and direction of vectors from the GNSS module.
As far as I understand, protocols - be it NMEA or UBX - are just a “mechanism” for transmitting data from the GNSS satellite to the information user.
Consequently, the GNSS receiver receives all the necessary information for calculations.
I am sure that the ability of the UBX protocol to produce data on speed and vectors is due to a proprietary function.
But theoretically and mathematically, how can vectors and velocities be calculated from GPS data?