I want a way to get accurate time into a project I’m working on, so I’m thinking of using a GPS receiver.
But all the GPS units I’ve found provide position, and hence require at least three clear signals, right? But for time I’d only need one (and hence not need to wait for a lock).
Does such a thing exist as a GPS time module?
Thanks for any advice.
There are indeed “GPS” units designed strickly for time. The Trimble Resolution-T comes to mind. This unit will provide time accurate to 20 nanoseconds with about a 50 nano second jitter (if memory serves me right).
You can get time with just one SV but you need to tell the unit exactly where it is located (lat/long/elv). The whole thing with GPS is that you have four variables you are trying to solve for: Lat, Long, Elv, and TIME. You therefore need four equations to solve for your four variables. These equations are created from signal propogation from four SVs. If you know where you are, then you only need one equation to solve for time.
The question is, how good a time do you need? Do you want the closest year, month, day, hour, minute, second, millisecond, microsecond, nanosecond, or picosecond.
The other thing is that most GPS receivers do output a time hack message. Read up on your unit’s output messages.
SV = Satelite vehicle