[time-nuts] iGPS?

Bob Camp kb8tq at n1k.org
Tue May 19 10:49:32 UTC 2015


Hi

If we’re talking about a corrected survey receiver, you can get a *lot* better than 1 M. Single
frequency corrected (WAAS etc) fixes from multiple systems (GPS + GLONASS + …) are
indeed doing ~ 1 M (horizontal) in urban environments. The correction data is often applied via remote
acquisition (cell tower or what ever). For $10 you can get a multi system USB stick from China. 
That’s a setup that will fit into a cell phone. 

You can check and see if you are off by 50M fairly easily. Things like bridges and cross roads are
fairly easy to spot. The “put me on the road” algorithm has very little to do with their location. If you are 
off by 1/4 block, you’ll notice. 

Unless Apple *buys* them ( => iRidium), I don’t see them going for anything other than subscription 
plans for their service. They simply have to much ongoing overhead. That’s been the problem
since Motorola was involved and it’s their problem today. 

Bob

> On May 18, 2015, at 10:59 PM, Chris Albertson <albertson.chris at gmail.com> wrote:
> 
> Yes GPS can do => better than 50M but we are talking about a single fix
> from a cell phone in a moving car not a survey receiver.  .  The
> displayed location is better because the phone applies a filter to the
> location data.  Some thing like a Kalman filter.   I doubt the iPhone
> can get within 10M from a moving car.
> 
> As for Iridium being an expensive for pay service.  But that is
> because most users SEND data.  This new service is broadcast and costs
> do not depend on the number of users.   Apple has sold 130,000,000
> phones already just in this half of 2015.  A one time payment of about
> $1 per phone might cover the costs.
> 
>>> hmmmmm……I do believe the marketing boys have been playing with the
>>> numbers. You would have to start
>>> from a >50 M error to get them to make much sense based on what they are
>>> doing.
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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