Sunday, April 5, 2009

The iPhone as a GPS Device

The iPhone is a tantalizingly useful GPS device. First of all, it is being used with one hand tied behind its back, as it were. This is because I've turned off data-roaming for the present. This is because I've exceeded my 7 MG pro-rated quota by a meg or so. I'll have 20 megs as of April 7th, but it is very easy to use 1-2 megs at a time getting a map under the pulsing blue dot.

What is interesting is that the the roaming 3G continues to take GPS fixes via UK Vodophone. I don't think there is an additonal charge for this, but it hasn't shown up in the usage stats or in the ATT wireless online statement (though it runs several days behind). The iPhone mapping app (integrated with Google maps) typically would gather the needed information by wi-fi and display a route over a detailed map. I would often calculate a route (as I did this morning) and then head out.

But with data-roaming turned off and no wi-fi, no map fills in. BUT the blue dot continues on along the route-track! The track will continue, as will the blue dot, off the edges of the known universe, i.e., off of the stored map surface. But the route remains intact, along with distances and turns, just over a gray background. This means the the iPhone does work WITHOUT data roaming turned on. Quite efficiently, too. The battery remains charged for a long period of time.

It's fun, too, to suddenly discover the map filling in under the route! This occured near the Fengchang restaurant when my iPhone captured a free wi-fi hot spot - automatically, as always. Suddently, I had my map overlay (or underlay) in the vicinity of Regent's Park. I could see the park and park features there. Alas, the phenomenon didn't last long and I was back to gray surface, but again with my route track and directions intact. The iPhone would be full-featured as a GPS unit if it passed by a series of wi-fi hotspots (would Panera's ever alternate with Starbuck's -- ah well, Starbuck's is still mostly T-Mobile, which is not free). But the routing feature even over a gray background is still useful.

My Garmin 60Csx, by the way, was quite frustrating on this outing. It was slow and was continually baffled by tall buildings. It was possible to "find" a particular restaurant (though the Fengchang was not in the database) or tube stop, but it requres quite a bit of time inputing the inquiry information and the Garmin doesn't give stable, consistent responses. As a result I had quite a long detour near the East Aldgate underground to which I was directed because of the closing of the Circle, District, and Hammersmith lines this Sunday.

A couple of days ago, I approached the Tower of London from Aldgate and snapped a picture of Traitor's Gate when I got there.

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