On Wed, 12 Dec 2018 22:36:49 -0000, "NY"  declaimed the
following:

>
>That's interesting. I'd have thought that with a good aerial and no
>obstructions so you can see lots of satellites you should be able to get
>very good results.
>
 For ground speed, not air speed... Having a 200kt ground speed with a
100kt tail wind means an air speed of only 100kt.

>My phone varies between about 20m and 5m radius of error for lateral
>movement. Not sure how accurate it is for altitude. I sometimes find that I

 I believe convention is to assume vertical error is 150% of lateral.
Your phone is also most likely using just the C/A signal; airlines may be
able to get decryption keys allowing use of the precision signal. I don't
even know if any consumer level GPS is able to make use of dual frequency
signals yet -- the precision signal is sent over two (or now, maybe four)
frequencies, allowing the receiver to correct for ionospheric delays. C/A
traditionally was sent on one frequency only.


--
 Wulfraed                 Dennis Lee Bieber         AF6VN
 wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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