[time-nuts] Averaging Location for Position Hold

[jmfranke]

I believe that should read WGS 84 not WPS84.

John  WA4WDL

--------------------------------------------------
From: "Chris Albertson" <albertson.chris at gmail.com>
Sent: Tuesday, September 13, 2011 5:03 PM
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Subject: Re: [time-nuts] Averaging Location for Position Hold

> 2011/9/13 Miguel Gonçalves <mail at miguelgoncalves.com>:
>> Hi all!
>>
>> I am installing a timing GPS unit over a new location where I already 
>> have a
>> NMEA GPS with PPS (let's call it unit A). The NMEA GPS is logging every 
>> 16
>> seconds its GPGGA string.
>
> The Oncore UT+ can does it's own site survey automatically.  That's
> the best way.
>
> You can only compare the GPS location with Google if both are using
> the same "system".  The most common one today is WPS84 but you need to
> check.
>
> The problem is that the Earth is not a Sphere and different systems
> assume non-sphere shapes.  Getting this wrongs gives about the size
> error you observed, more or less.
>
> Also, can you really trust Google Earth as an authoritative source?
> I'm not sure.    An interesting test would be to go find a USGS
> benchmark or a section marker near you then enter it's location into
> Google.  See if Google hits the marker.
> -- 
>
> Chris Albertson
> Redondo Beach, California
>
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