I don't know, but I suspect that for some reason, the used definitions of what that means now must be different! As i said higher up in the post, there are several different models of "GPS" Two that can acquire a fix for somebody that can deliver a fix sooner are AGPS and post-processing on another machine. Neither is available to most people 'in the middle of nowhere' say, if they are on a boat, without net access. Then they are either going to leave the GPS on all the time (always a good idea since they take almost no electricity) or wait that time after its turned on, unless by some fluke, they already have the data.
(Edit- the absolute minimum time to download both ephemeris and almanac is stated to be 12.5 minutes for example, below:
https://en.wikipedia.org/wiki/Time_to_first_fix )
Hamster, there is definitely some definitional misunderstanding as to what means what.
I'd like to see more info if you have it.
This only holds for GPS, not other GNSS systems....
To acquire a space vehicle's data, you have to look for each of the 30 or so space vehicle's random number across about 10kHz of bandwidth, at 2048 different phase alignments. Doing this requires up to 2 million attempts to perform an exhaustive search for all space vehicles. This is why a cold start used to take so long....
Once the receiver has acquired the signal, it starts tracking the space vehicle. This gives it access to the 50 bits per second of BPSK data being transmitted.
This data is formed into NAV message frames, - there are five different 300-bit subframes, each taking 6 seconds to transmit.
- Subframe one has the timing correction for the transmitting space vehicle
- Subframe two and three has the precise orbital information
- Subframe four and five have the pages of the almanac. (IIR there is 25 pages in the almanac).
Once you have subframes one, two and three you can calculate the position of a given space vehicle at a given time (within a time window around the transmission time) - you don't really need the Almanac information in subframe four or five to get a location fix.
This is because the orbit information in the Almanac have less precision and are only approximate. However, if the receiver knows approximately when and where you are, you can work out which space vehicles you can see in the sky, and it might also be able to calculate the doppler shift. It can then prioritize these optimize the search to try and find these signals first, speeding up the time to first fix - however it still needs to get the detailed orbital information from the current NAV messages to give a fix.
The upshot is the data in the Almanac speeds up only acquisition of the space vehicles, but doesn't really feed into the tracking or positioning (except for a few correction values that can improve accuracy).
GPS receiver hardware has advanced to the point where the almanac is of little use. For practical purposes you can search for all signals on all channels at once, so the time to first fix with and without the almanac is approximately the same.
As an example. one way to do this is to take the FFT of 2ms of data, then convolve that against the precomputed FFTs of the space vehicle's random signature. This gives you very good information of the power levels, signal phase and doppler shift for all space vehicle in that 2ms of data, allowing you to acquire the space vehicles very, very quickly, with only 2ms of data.