Basic Questions

[thebixman]

I have a GPSlim 236, HP1945, and iGuidance 2.1. Everything works perfectly, but I'm curious....

1) What is Hot/Warm/Cold start, and how does this impact the iGuidance performance? If I select Hot start in my GPS testing software, will it work better than a Cold start? I understand there's a difference in timing between the 3 starts (different "seconds"), but haven't a clue what it all means.

2) Is one baud rate better than another? The Holux manual references 38400 as a testing value, but within iGuidance if I go from 4800 to 115000 will I notice anything?

Thanks

[Sven Johannsen]

The differences between the types of starts refer to the initial conditions provided to the algorithms that calculate your position. To figure out where you are the unit needs to solve four equations with four variables. The typical way of doing this in a computer is assuming some values and calculating the others iteratively until you zero in on a solution. If you are close to begin with, the process doesn't take as long. A cold start is when the GPS has no clue where it is and has to calculate from scratch. A warm or hot start is when you give it a clue, either by entering a starting point, like your state, or you aren't far from the last time you calculated your position.

Some will likely disagree, but I don't expect you'll see much difference based on the data rate. The GPS calculates lat, long, elev, time and provides the GPS display software those parameters along with some satellite info via text strings. Pretty much the best update rate you see on GPS displays is once per second. Whether you go 4800B (NMEA standard) or 115KB, the minimal amount of data can get to the display (PPC. Smartphone) much faster than the 1 sec update.

[thebixman]

Thanks Sven.