[hpsdr] Fwd: 1, 2, 3, 4, 5, 6, 7....

[Glenn Thomas]

Also, keep in mind that the GPS system specification calls for a C/A 
solution accuracy of about 100' CEP. In the lat & long, that doesn't 
seem like very much, however we seem to be a bit more sensitive about 
altitude. - Glenn

On 7/26/2012 8:25 AM, John Ackermann N8UR wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> I don't know if that's true (you may be thinking of the old Selective 
> Availability, which was turned off quite a while ago). As I understand 
> it, the main issue is that the geometry of the satellites just doesn't 
> allow as precise a fix of altitude as it does the other axes.
>
> To get best accuracy in altitude, you'd like a fix that includes 
> reference points both above and below your location.  But the GPS 
> can't see satellites that are below the horizon, so the quality of the 
> fix suffers.
>
> John
>
> On 7/26/2012 11:15 AM, Tim O'Rourke wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>>
>>
>> US goverment keeps some of GPS altidude capability vauge for security
>> purposes.
>>
>>
>>     -----Original Message-----
>>     From: Alberto I2PHD
>>     Sent: Jul 26, 2012 10:58 AM
>>     To: HPSDR list
>>     Subject: Re: [hpsdr] Fwd: 1, 2, 3, 4, 5, 6, 7....
>>
>>     On 7/26/2012 1:42 PM, Simon HB9DRV wrote:
>>>
>>>     I have a Thunderbolt on my balcony; using Lady heather I can
>>>     confirm that my house hasn’t moved by more than a few cms in the
>>>     last year J
>>>
>>     Have you checked the altitude too ? My Thunderbolt tells me that
>>     from the morning to the evening of the same day
>>     my house moved up and down by almost 30 meters.... :-)   and the
>>     antenna is firmly attached to one of the chimneys....
>>
>>     I guess that is one of the reasons why GPS is not used on any
>>     aircraft, at least as an altitude measuring device...
>>
>>     --
>>     /*73 Alberto I2PHD*/
>>
>>
>> Tim O'Rourke
>> W4YN at ARRL.Net
>> Low Power Amateur Radio Rocks
>> Member of Flying Pigs,ARCI,GQRP,RSGB,ARRL Life Member
>> NHRA Life Member
>>
>>
>>
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