Using GPS on phone whilst abroad

pepdavies

Does agps work with WiFi? You could get a fix on arrival in the country this way. I remember buying a garmin handheld from Hong Kong. It took 45 minutes to get its first fix in England. It was fine afterwards.

securityguy

pepdavies wrote: »

Does agps work with WiFi? You could get a fix on arrival in the country this way. I remember buying a garmin handheld from Hong Kong. It took 45 minutes to get its first fix in England. It was fine afterwards.

Yes, AGPS originally was just about getting ephemeris and almanac data, but these days any phone which says AGPS will also try cell-tower triangulation and WiFi SSID location via Skyhook.

Older Garmins, like my 1994-vintage GPS12, allow you to input your rough location (country or US state), which also helps.

This is worth reading, as it defines the various start states for GPS receivers: http://www.gsmarena.com/glossary.php3?term=gps

Cold Starts can easily take 45 minutes: the ephemeris data is only broadcast at a very slow rate, so you have to listen for 30 minutes to get a complete set. After that, you have to try to acquire each satellite in sequence until you identify the set that are in view. As they all broadcast on the same frequency, this isn't quick. I've got a little GPS receiver hooked to a Raspberry Pi that I use as a time reference, and only after a few 45 minute outages realised that as the receiver had no onboard power and I was powering it off the Pi's regulator, every time I power-cycled the Pi the GPS had to cold start. Ah, _that's_ why there's a pad for a battery on the circuit board! A few minutes' soldering and it maintained its clock and data over power cycles and hot-started in a couple of seconds.

RumRat

waterwatereverywhere wrote: »

Hello

Just a a quick message to say many thanks to everyone for all the helpful and detailed replies.

I'm going through these now to try and understand it all.... (not very techie!)

In the meantime I'm downloading Navfree to give that a try. If there are any other free Android Apps like this which are similar or better which I could also try out I'd be grateful for any suggestions.

Thanks again.

Post #4 for another free SatNav recommended.

DCFC79

Another option is to use google maps and download the maps you need or buy co pilot for android and use that which doesn't use a mobile data connection just gps.

poppy10_2

I used Osmand free offline maps for my recent holiday. Worked really well. You download the maps before you go, and then when you are abroad you use the maps offline without any data charges (you can switch on airplane mode if you are worried about the phone using up data).

It's free and open source. There's a paid version that allows you to download more than four countries at a time but that's not really necessary for most people

https://play.google.com/store/apps/details?id=net.osmand