Satellite Status Screen and the Altitude of the Sats

[+Iowa Tom]

Does anyone know if the satellite status screen lists all the GPS satellites above the horizon or is there an above 5 degree low limit etc? My Magellan showed one that was, according to CalSky, only 8 degrees above the horizon. It did not show one that was 6 degrees up though.

 

You can check your own GPS screen with the list of what's up for your IP address here?. Simply adjust the Minimum elevation of satellites then hit “Now.”

 

I noticed (for the first time) tonight that just as CalSky starts with the highest altitude sat on top so my Magellan starts with the highest sat on the left in the list at the bottom of the screen.

 

-it

[+HaLiJuSaPa]

Does anyone know if the satellite status screen lists all the GPS satellites above the horizon or is there an above 5 degree low limit etc? My Magellan showed one that was, according to CalSky, only 8 degrees above the horizon. It did not show one that was 6 degrees up though.

 

You can check your own GPS screen with the list of what's up for your IP address here?. Simply adjust the Minimum elevation of satellites then hit “Now.”

 

I noticed (for the first time) tonight that just as CalSky starts with the highest altitude sat on top so my Magellan starts with the highest sat on the left in the list at the bottom of the screen.

 

-it

 

From what I've read, most GPS devices have a 5 degree low limit. But it is based on the idea that below that, the receiver is either not going to get the signal or it will be a very degraded one. But it may not show one that is close (i.e. 6 degrees) if the signal is extremely weak. Some may let you adjust this limit as well.

[John E Cache]

Does anyone know if the satellite status screen lists all the GPS satellites above the horizon or is there an above 5 degree low limit etc? My Magellan showed one that was, according to CalSky, only 8 degrees above the horizon. It did not show one that was 6 degrees up though.

 

You can check your own GPS screen with the list of what's up for your IP address here?. Simply adjust the Minimum elevation of satellites then hit “Now.”

 

I noticed (for the first time) tonight that just as CalSky starts with the highest altitude sat on top so my Magellan starts with the highest sat on the left in the list at the bottom of the screen.

 

-it

Interesting. The bottom four in the list are the optimum constellation for me. If that is always true, the lower the elevation the GPS uses the better the accuracy.

 

The 60csx antenna has gain in a 60 degree cone. Which explains why an external antenna is seems more accurate.

 

Also, elevation for airplane pilots who use an altimeter is different than elevation for ships pilots who shoot the stars with sextant. One is an altitude and one is an angle. I wonder if the altitude of the sats change or if they are in a circular orbit?

[+Iowa Tom]

From what I've read, most GPS devices have a 5 degree low limit. But it is based on the idea that below that, the receiver is either not going to get the signal or it will be a very degraded one. But it may not show one that is close (i.e. 6 degrees) if the signal is extremely weak. Some may let you adjust this limit as well.

 

Thanks HaLiJuSaPa,

 

The screen data is from an ephemeras stored in the software I believe. So what I was seeing was satellites that were "supposed" to be there, regardless of a signal. The number of satellites on the screen doesn't increase when the GPSr starts receiving signals.

 

Here is a picture of the satellite status screen on one of my units during a spectacular aurora over NE Iowa. I was getting full signals from 10 out of 11 satellites on the screen!

 

[+Iowa Tom]

Also, elevation for airplane pilots who use an altimeter is different than elevation for ships pilots who shoot the stars with sextant. One is an altitude and one is an angle. I wonder if the altitude of the sats change or if they are in a circular orbit?

Great stuff John,

 

I just checked and the highest GPS sat in my sky at the moment is 69.9 degrees. It's also 20,436.5 km away. The distance to the GPS sats compared to the elevation within the troposphere should be negligible.

 

Their orbits are called intermediate circular orbits.

Edited March 3, 2007 by Iowa Tom