[time-nuts] time-nuts Digest, Vol 130, Issue 27

[Bob Camp]

Hi

The gotcha is that the GPS numbers are related to a geoid model and not to sea level. 
You can indeed find points that are “underwater” based on the geoid, but quite dry in 
real life (and vice-versa). 

Bob
> On May 19, 2015, at 12:26 PM, Demian Martin <demianm.pds at gmail.com> wrote:
> 
> I would buy that (Google Maps being off) except that I'm less than 2 miles from the SF bay and -5M would have me underwater. That may well happen but not for a few years at least. Also the Arbiter does match Google maps pretty closely. It doesn't really matter a lot, just a curiosity.
>     Demian
> 
>> Date: Mon, 18 May 2015 18:12:58 -0400
>> From: Bob Camp <kb8tq at n1k.org>
>> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
>> Subject: Re: [time-nuts] Thunderbolt Height Error
>> Message-ID: <1AE37B6B-35FD-4C5F-95D6-01316D6C4AE1 at n1k.org>
>> Content-Type: text/plain; charset=us-ascii
> 
>> Hi
> 
>> The simple answer is that Google maps may or may not be correct. There are a lot 
>> of examples of them being off by 10M or more. That said, my *guess* would be that the 
>> Thunderbolt is closer to the truth.
> 
>> Bob
> 
>> On May 18, 2015, at 2:34 AM, Demian Martin <demianm.pds at gmail.com> wrote:
>> 
>> I have 2 GPSDO's. A Thunderbolt and an Arbiter 1083A. The Arbiter is old but
>> it works fine (and has a Wenzel 5 MHz streamline oscillator in it). It has
>> the 1995 firmware issue, and I could get new firmware for it ($$) but I'm
>> not using it as a clock, just a frequency source.
>> 
>> 
>> 
>> I just moved and have re-setup both. They share an antenna. I got both to do
>> a self survey. The Arbiter was really close to what Google maps indicate is
>> my location. The Thunderbolt was about the same except it has me
>> underground. The arbiter has the height as +30M. The Thunderbolt as -6M.
>> What setting do I have wrong in the Thunderbolt? Would it affect the
>> operation as a frequency standard in any way?
>> 
>> 
>> 
>> 
>> 
>> Demian Martin
>> 
>> San Leandro, CA 94577
> 
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