GPS satellites visible over a location on earth

Hi,

Can anyone please tell me where I can get the information regarding
satellites visible to a receiver given the location of the receiver
and the time.
Thank you in advance.

Regards,
GPS Baseband.

 

http://www.calsky.com/?GPS=

 

Thanks a lot.

 

My many-years-old Garmin eMap does this automatically. Slew the
location cursor anywhere on the globe and it does the same. Your
machine doesn't?

 

You could also look at:

http://www.nstb.tc.faa.gov/RT_WaasSatelliteStatus.htm to see
where each GPS is at the current time.

Slew through the prior day's video to see where they are at a time
other than the current. Positions are 4 minutes earlier every day.

 

Nice page, Tom.

Could you explain why the GEOs are highlighted as NPA?

Regards,
Jon

 

I'm going to guess that the position info of those satellites aren't
used for precision approaches, just the data they transfer for WAAS.

 

The governing spec for airborne WAAS equipment RTCA DO-229
requires the User Differential Range Error (UDRE) to be 15 m or less
before a ranging source is a allowed in a precision approach
(vertical
navigation) solution. The GEOs can be used as ranging source for
Non-precision approach (horizontal only) if the UDRE is 150 m or
less.
The GEOs can also be used any time the UDRE is other than Do Not
Use or Not Monitored in non-safety of life applications.

The WAAS GEOs currently have an artificial UDRE floor of 50 m.
UDRE is a 4 bit number, 50 is the next size after 15. That floor will
be
changed to 7.5m later this summer when the next version of WAAS
software is fielded.


Tom