[time-nuts] altitude difference between two gps

[Norman J McSweyn]

James R. Gorr wrote:
> Yes.  The pending leap second has me very scared.  It is the Y2k bug of 2008.  :-)
> 
> Sorry, that is a tilde, not a negative sign.  Meant as "approximately" 791 meters, although I may be using it completely wrong.  The real value (mean average) is 790.83 meters for the Sure Electronics GPS.
> 
> Sorry for the confusion.  
> 
> --- On Sat, 12/27/08, Richard W. Solomon <w1ksz at earthlink.net> wrote:
> 
> From: Richard W. Solomon <w1ksz at earthlink.net>
> Subject: Re: [time-nuts] altitude difference between two gps
> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
> Date: Saturday, December 27, 2008, 7:24 PM
> 
> -800 meters ??
> Live in a mine ??
> How can that be ?
> 
> 73, Dick, W1KSZ
> 
> -----Original Message-----
>> From: "James R. Gorr" <n3toy at yahoo.com>
>> Sent: Dec 27, 2008 9:26 PM
>> To: time-nuts at febo.com
>> Subject: [time-nuts] altitude difference between two gps
>>
>> Hello everyone!
>>
>> I have a tbolt that I am monitoring with tboltmon.exe and some off-brand 12 channel GPS (I bought from Sure Electronics on eBay) that I am monitoring with VisualGPS.  Both are fed from the same GPS antenna through a symmetricom splitter.  There is a 30 meter difference in the altitude readings between the two.  My tbolt says my altitude (after a self-survey) is ~761 meters and the 12 channel Sure Electronics GPS says my altitude is ~791 meters after 7,500+ readings.  I took my hand held Garmin 12XL outside and it says my altitude is ~790 meters at street level.
>>
>> Anyone have an idea why my tbolt might be reading different from the other two devices?  I am assuming the tbolt is reading low. 
>>
>> Jamie
>>
>>
>>       
>>
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> 
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>       
> 
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My m12+t and Thunderbolt were doing the same thing (non agreement in 
height). They do share the same antenna. By setting the antenna mask 
angle to the same value on both gps units, the difference was less than 
one meter.
Norm n3ykf