using a GPS

[GPSGuided]

Forgot to mention this: When the time is sent on a different frequency it is easier to correct for ionospheric delays, this means that 2 satellites near each other but sending on another frequency improve accuracy more.

Rephase:
The ionosphere changes the speed of the signals coming from the satellites, but the amount of delay changes with time and frequency.
An extra GPS satellite in the same part of the sky does little to improve accuracy.
An extra GPS satellite in the same part of the sky but broadcasting at another frequency does a lot more to improve accuracy as it can be used to calculate the ionospheric delay.

Icefest, what did you say you are studying? Professional vacuum of Internet knowledge?

Very interesting. Is this parameter actually used in our consumer level GPS units?

[jonnosan]

just to clarify - my question about what can go wrong between map & compass vs handheld gps is not about what is possible, it's what is more likely.

As an anecdote, I have personally witnessed 2 walks where the leader's compass has failed, and seen 0 failures of a GPS.

[GPSGuided]

Compass failure? That's one very very very very very unlucky guy! LOL

PS. Suggest that you should never follow those "leaders" again.

[icefest]

Very interesting. Is this parameter actually used in our consumer level GPS units?

Some do, I'm not sure which ones.


WAAS and EGNOS achieve the same but require physical infrastructure that Australia does not have. (Leave them disabled to save battery power)
The aviation idustry is hoping to get a system like this up and running in Australia which should improve single band GPS accuracy to >50cm.

Have a read of this segment of this Wiki page: http://en.wikipedia.org/wiki/Error_anal ... ic_effects

[vicpres]

For what it's worth, here is the latest on MAP technology: http://www.youtube.com/watch?v=ZCp-JSVSNZM