It cannot be instantaneous as it is digital not analogue and what's more the satellites transmit in turn. Theoretically you can get a reading at 1kHz but this is totally in the message (PSK) phase noise so there is nearly zero accuracy. Some modules update at 25Hz these days but will need tons of external processing because of the jitter/noise and there is almost certain possibility these modules are working predictively rather than empirically because the source data is simply not there to measure that fast.Again, a GPS module is able to measure instantaneous velocity (vector of speed + direction) relative to multiple satellites by using Doppler shift, actually more precisely than position.
Also nowadays there are modules working at 10 Hz rate instead of traditional 1 Hz, that's far from nonsense.
For 10Hz update you would be limited to receiving 5 satellites because of the 20mS pulse rate of each satellite and the code division multiplexing which is pseudo-randomised (you can't guess which source a single bit comes from), it is also roughly the difference in time between nearest and furthest satellite. 5 satellites don't give you very good noise immunity especially in the vertical axis.
Don't underestimate accelerometers, I've seen drones regularly return to start within 1 inch after 3 minute flights using only inertial navigation (an accuracy which can't be achieved repeatedly using consumer level GPS, you might have the occasional fluke), the faster you read the more accurate the integration will be and most mountings remove any short spikes that could occur between samples. With GPS it is pointless integrating data that has already been predicted and expecting improved real time accuracy, you are drawing ghosts out of yesterday's shadows.
Statistics: Posted by pidd — Sun Jul 13, 2025 5:43 pm