Extend QuickGPS data validity?

[hvn99]

I'm going abroard where data costs an arm and a leg... Any way to extend the validity of the QuickGPS datafiles to enjoy fast gps fixes for more than the standard 7 days?.

There will be no access to a computer with active sync on the trip and my phone plan does not provide gprs/umts data abroad. What do I do to avoid that very long fix time without the aid of QuickGPS?

[lthown]

the only way to do that would be to modify the actual satellites orbiting the earth so they move in a more predictable pattern and the ephemeris info isn't needed

in short - no, there's no way to do it. QuickGPS is a shortcut to getting the position data from the GPS sats which send it at a painfully slow rate. The nice thing is - provided you use your GPS for an hour or so every few days, the info is up to date on your device and you'll still get quick locks.

I'd suggest spending some time with http://en.wikipedia.org/wiki/Global_Positioning_System

[Guilf]

I went through this at one point in time. I'll give you the answer that I was given (with the understanding that it could have changed). The reason that QuickGPS updates every 7 days is the ephemeris data is only provided by NGS (http://www.ngs.noaa.gov/orbits/) 10 - 14 days in advance. Not sure if this is a precision thing or a national security thing or if the data file would then become too large, but I was told that it was impossible to get it further out.

FYI - when I was searching, I found this simple explanation of how QuickGPS works. Thought it was interesting.

"Some other posts on the Wiki reference Quick GPS, but seem to mistake what it does, so I thought I'd clear it up, being a professional in the space.

Quick GPS does not "triangulate" using cellular networks, not even close. Let me start by telling you how a GPS gets a fix on its location, and then explain how Quick GPS offers a shortcut.

The GPS chip receives a synchronized timed signal from the satellites (birds) the US DoD launched into orbit. Each bird uses a different channel. With a good signal from three or more birds, GPS starts to get a fix. It does this by calculating the time difference between the reception of the different signals, then calculating the relative distances to each of the birds, then figuring out where it sits in the middle of the birds.

The GPS calculates four spheres, and its located somewhere on the surface of each of these spheres. There is only one point where these four spheres intersect. That's you.

If you're good at geometry, you might think that it needs 4 birds to get a fix, but in fact, if the GPS assumes that you are on earth, that provides another sphere, so it only requires 3 birds to get a decent fix. More adds altitude and accuracy.

But the GPS needs to know where each of the birds is before it can decide where IT is. That information is not calculated, but is available in a detailed download of orbital data provided by the DoD called ephemeris data. It is transmitted...from the bird to your GPS. For a cold start, your GPS needs to download the entire file, without interruptions in the signal - BEFORE it can even start getting a fix. In fact, the GPS may not even know which channels to tune into, since it doesn't yet know which birds are currently overhead. This causes a slow first fix.

Quick GPS, is simple. Ephemeris data is passed thru WiFi or cellular data connection ahead of time, and you never have to wait for it to download over the satellite. Awesome."