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  EGNOS Goes Operational

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Author Topic:   EGNOS Goes Operational
jimh posted 10-08-2009 09:08 PM ET (US)   Profile for jimh   Send Email to jimh  
The satellite based augmentation system (SBAS) EGNOS, or European Geo-stationary Navigation Overlay System, became operational on October 1, 2009. This SBAS is similar to the FAA's WAAS system. It is similarly transmitted from geo-stationary satellites. EGNOS is using the following psuedo-random noise (PRN) code numbers and satellite locations:

PRN 120 = 15.5° West aboard Inmarsat 3-F2
PRN 124 = 21.5° East aboard Artimis

For users in North America, only the signal from Inmarsat 3-F2 would be usable. From the Midwest, say around Detroit, the look angle to Inmarsat 3-F2 is not particularly good:

Look Angle to satellite at 15.5° West from Detroit, Michigan
Azimuth =105°
Elevation = 7.75°

This is a rather low elevation and long path. Curiously, in August we were several hundred miles to the East, in the St. Lawrence River, and I noticed that my GPS was occasionally reporting reception of a signal from PRN 120. Perhaps it was receiving Inmarsat 3-F2's signal.

For a user on the Eastern seaboard, the EGNOS may offer better availability. The look angle to Inmarsat 3-F2 from the coastal area of South Carolina, for example, will be

Look Angle to satellite at 15.5° West from Charleston, South Carolina
Azimuth =104°
Elevation = 12.5°

Many modern GPS receivers support precision fix augmentation using EGNOS. It would be interesting to hear if any boaters in the Eastern U.S.A are able to utilize EGNOS. Also, reports from European boaters would be equally welcome.

For more information:

http://www.esa.int/esaNA/SEM2HGF280G_egnos_0.html

SJUAE posted 10-10-2009 01:32 PM ET (US)     Profile for SJUAE    
Jim

This application for the IPhone thats free should help locate and see if you can spot them from your location

Satellite Tracker:

"Track satellites as they pass over your location. This application allows you to select any number of satellites and will show the track through the sky of the next pass(es) of each over your location. Frequency information can be added so you know how to tune into the signals. The satellite information is downloaded via the internet, and the iPhone GPS can be used to automatically track your location. Options allow the display of the sun and moon locations and the angle of the iPhone/iPod Touch to indicate to guide where to point your antenna. This application is primarily intended for those who use the Amateur Radio satellites but weather and other satellites can also be tracked."

http://www.uquery.com/apps/306260378

I think I got the three you noted but searching for EGNOS on the app gave me another two:

AOR-E and IOR-W

regards
Steve

jimh posted 10-10-2009 04:44 PM ET (US)     Profile for jimh  Send Email to jimh     
The satellites used for EGNOS are in geostationary orbit. The elevation and azimuth to them do not change with respect to terrestrial observers.
jimh posted 10-11-2009 09:17 AM ET (US)     Profile for jimh  Send Email to jimh     
To calculate the look angle to a satellite in geostationary orbit, you can use this calculator:

http://www.intelsat.com/resources/satellitedata-pas/calc-look-angle.asp

(The calculator is linked from the above resource.)

This calculator is handier than most because you can just enter the geostationary orbit position of the satellite by its longitude. You can also enter your position by latitude and longitude.

SJUAE posted 10-11-2009 02:23 PM ET (US)     Profile for SJUAE    
Jim

This little Iphone app calculates and shows the position ( Range, Az Elv, Alt, Vel) relative to your current location or any other location you choose regardless if they are geossynchronous or otherwise.

So you don't see a track for geosynchronous satellites.

Maybe thier description was a little missleading but this seems a lot easier as all you do is pick your satellite from the large list provided and use the displayed results calculated using your Iphone gps postion or manually selected location, to point to it, if it's above the horizon.

Regards
Steve

jimh posted 10-11-2009 09:00 PM ET (US)     Profile for jimh  Send Email to jimh     
Regarding the naming convention of geosynchronous orbiting satellites, there are three typical designators:

--the orbital station, designated by longitude;

--the position name in a particular constellation for a particular provider; and,

--the individual satellite designator, unique to the satellite and not its orbit or position.

This chart helps to understand the naming for Inmarsat satellites:

http://www.marinetelecom.net/Inmarsat-Satellite-System.html

For example, satellite at 15.5-degrees West is called AOR-E (for Atlantic Ocean Region East) and is currently provided by the Inmarsat-2 F2 satellite.

The satellite oribiting at 64-degres-East is referred to as IOR (for Indian Ocean Region), and is currently provided by the Inmarsat-3 F1 satellite.

jimh posted 10-11-2009 09:09 PM ET (US)     Profile for jimh  Send Email to jimh     
Most GPS receivers, at least the ones used on small boats, do not have an antenna that requires pointing or tracking to receive signals from satellites. The GPS receiver antenna just needs a clear view of the sky. The GPS satellites orbit in a non-geosynchronous manner, and their position is constantly changing with respect to a ground station. The geosynchronous satellites do not change orbital position with respect to a ground station, unless of course the ground station's GPS receiver is moving. However, at the rate of speed which a small boat can move, the look angle to a geosynchronous satellite will change only very slightly, so you can consider the look angle to be more or less constant for a particular area or region.

As I mentioned early in the discussion, I did see some recent attempt by my GPS receiver to receive a signal from a source with PRN 120. The signal would come and go, which I attribute to the low elevation angle and marginal strength. I am still interested in hearing of reports of recreational marine GPS receivers getting a position fix augmented with EGNOS. If anyone has a GPS and has received the EGNOS augmentation signal, please let us know by joining this discussion.

jimh posted 10-17-2009 02:15 PM ET (US)     Profile for jimh  Send Email to jimh     
The footprint of AOR-E coverage is seen in the linked graphic below:

http://continuouswave.com/whaler/reference/graphics/AOR-E.png

The cutoff for the coverage plot is an elevation angle of 5-degrees. The area within the yellow box is the area for which precision fix augmentation is provided by EGNOS.

SJUAE posted 10-17-2009 06:48 PM ET (US)     Profile for SJUAE    
I found this colour one by chance

http://i707.photobucket.com/albums/ww76/SJUAE/Stern%20and%20misc/ egnos-footprints.jpg

Shame I did not have a modern portable marine gps to try out for you, as I'm on my way to Brazil via UK

Regards
Steve

Chuck Tribolet posted 10-17-2009 08:53 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Jim's yellow rectangle is important. EGNOS doesn't have an
differential ground stations on this side of the pond, so
EGNOS isn't going to do East-Coast Americans any good.

WAAS on the other hand, has about 38 ground stations in the
US (inc. Hawaii, Alaska, and Puerto Rico), Canada, and Mexico.
WAAS is the way to go in North America.


Chuck

jimh posted 10-18-2009 11:38 AM ET (US)     Profile for jimh  Send Email to jimh     
Also, to make clear a point which may not be fully understood, the precision fix enhancement provided by EGNOS is for augmenting and enhancing the precision of the U.S. Department of Defense's NAVSTAR satellite navigation system (or "GPS" as everyone calls it). EGNOS is not its own, separate satellite global navigation system. It is just a precision augmentation for GPS for the European region, just as the FAA's WAAS is a precision augmentation for North America.
jimh posted 10-18-2009 11:51 AM ET (US)     Profile for jimh  Send Email to jimh     
I am a bit confused about the Indian Ocean EGNOS satellite. The graphic mentioned above shows NMEA ID 44 which implies PRN 131. The website of EGNOS mentions PRN 126, which implies NMEA ID 39. The best source of authority on PRN code assignments is

http://www.losangeles.af.mil/shared/media/document/AFD-090206-044.pdf

Using the Air Force publication as a guide, there seems to be some confusion about which satellite is active:

PRN 126 = NMEA 39 = IND-W =25°E =Inmarsat 4-F2

PRN 131 = MNEA 44 = IOR = 64°E = Inmarsat 3-F1

As a result, I removed my initial reference to this third satellite until it can be more correctly identified.

Chuck Tribolet posted 10-21-2009 09:36 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
WAAS also covers Hawaii, which would be Oceana, not North
America.
jimh posted 10-21-2009 09:39 AM ET (US)     Profile for jimh  Send Email to jimh     
Chuck--Thank for mentioning that WAAS covers Hawaii. This does not conflict with my statement that WAAS covers North America. WAAS covers both.

Have you any reception of EGNOS to report?

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