3 ms·
It seems that GPS signals can be used for higher accuracy if the receiving equipment uses two frequencies instead of one. This can freely be done by civilians,
by MikeDelta 3y ago
It seems that GPS signals can be used for higher accuracy if the receiving equipment uses two frequencies instead of one. This can freely be done by civilians, but requires more expensive equipment. Perhaps this solution with SBAS requires a cheaper setup?
https://www.gps.gov/systems/gps/performance/accuracy/ https://www.gps.gov/systems/gps/performance/accuracy/
- nradov 3y agoMulti-frequency GPS is already available in many inexpensive civilian devices such as smart watches and cell phones. It improves accuracy a little, primarily when the device doesn't have a clear view of the sky like when next to buildings. But it's still not as precise as SBAS.
- michaelt 3y agoThe highest precision GPS receivers require dual-frequency reception and perform "carrier differential GPS" - any time people are talking about GPS with 2cm accuracy, that's what they're talking about. The GPS signal has a digital signal (with a wavelength of ~300m) modulated with a sine wave (with a wavelength of ~20cm) - you can measure the 20cm signal much more precisely than the 300m signal, but it's 'ambiguous' because it repeats every 20cm and you don't know how many waves of the sine have passed. If you can receive two frequencies, giving you two slightly different sine waves, you can multiply them together and get a sine wave with a longer period, which (together with some clever maths) lets you bridge the gap between the unambiguous-but-imprecise digital signal and the precise-but-ambiguous sine wave. You also need a fixed base station at a known location - or access to a commercial network of such stations.