Re: [tlug] The Android Has Landed

[Curt Sampson <cjs@example.com>]

On 2009-07-11 07:33 +0900 (Sat), Shawn Brown wrote:

> Is GPS important to you -- for instance, would you want to track a
> child?  If so, you may want to NOT use softbank.  Apparently  GPS
> satellites (of all providers) shift to reposition themselves
> occasionally.  During that time, the GPS information will not be
> accurate.

Someone's fed you a line of total rubbish here.

GPS satellites are constantly shifting position; they're in orbit, after
all. But even when they move from one orbit to another, they always know
where they are, and will always provide accurate information which, if
you have it from four satellites (or three, if you have an accurate time
source), can be used to accurately compute your location. (See Wikipedia
or whatever if you want more details on this.)

The problem is most likely that the handset isn't getting enough good
fixes, which is not a rare thing. It would almost never happen indoors,
and even out of doors, buildings and other landscape features can result
in an insufficient number of fixes. (This assumes, of course, that
you've not done something silly like put it in a bag or pocket when you
want a fix, thus doing a great job of blocking all satellites.) What
handsets do in this case is estimate based on information from nearby
cellular base stations. This estimate can be dozens, or even hundreds
of meters off, which of course means that the indicated direction of
movement might also be wrong.

By the way, for others thinking about doing this, you may want to
consider that the primary purpose of it is not to mitigate an extremely
rare event (there are vastly greater risks to your children that
you ought to be addressing first), but to help parents with certain
emotional problems feel better.

cjs
-- 
Curt Sampson       <cjs@example.com>        +81 90 7737 2974
           Functional programming in all senses of the word:
                   http://www.starling-software.com