Coddy Posted March 20, 2004 Report Share Posted March 20, 2004 Hi all I checked out my chartplotter the other day to see if it would work on EGNOS and it located a number os satalites. I found a web page saying that they were testing the system and should be switching it on in April 2004. I am no electronics expert by any means but it seems they have been using a different mode for testing. Does anyone understand this system and can advise accordingly. Web page I found was http://www.pocketgps.co.uk/egnos.php Regards Codfather Quote Link to comment Share on other sites More sharing options...
Bob F Posted March 20, 2004 Report Share Posted March 20, 2004 Cod, I don't think they are using a different mode during the testing. Usually, a test signal will use the same mode as the operational signal, but the test signal cannot be relied on for accuracy or consistancy because they will be experimenting with different range and accuracy methods, and checking the error messages, etc. So, the test signal should not be used for applications where safety is paramount (e.g. a fighter pilot flying on autopilot at high speed and low altitude!!!) If the test signal is in operation I believe you should be able to pick it up, but it might not be there all the time. The difference between EGNOS and the old GPS system is in the accuracy (20m vs 5m) and with the messages you will be told the accuracy you are currently getting. The old GPS system uses the US (and Russian) military satellite system. These are self-contained satellites which transmit their signal to earth. EGNOS will still use the information from these satellites but it will use a series for ground stations which interogate these satellites to determine exactly where they are in the sky and then compute the errors due to atmosphere effects, etc. The corrected signal (with error information) is then transmitted from the base stations up to 3 EGNOS satellites which bounce them back to earth. If your GPS is EGNOS or WAAS compatible it is has a much more intelligent receiver in it which is able to decode the EGNOS signal and give you a more precise position fix, along with the error at your particular location, at that time. Your position is updated continually but the fix error is computed every 6 seconds. Not sure if this was what you were asking about?? cheers Bob F. Quote Link to comment Share on other sites More sharing options...
Paul D Posted March 20, 2004 Report Share Posted March 20, 2004 Bob, According to the link they are using a "type 0" test signal which may not be compatible with all GPS receivers. However, this will be a non issue in April when the system goes live. I cannot check if my Garmin is receiving the WAAS test signal yet ( and/or works with it ), because the satellite carrying the correction signal is near the equator and the house is between my boat and this !! Quote Link to comment Share on other sites More sharing options...
Paul D Posted March 20, 2004 Report Share Posted March 20, 2004 Found an even better link - page is still under development, but shows the status of the EGNOS signal. Mode 2 is currently in use, so all OK as of when I typed this !! EGNOS broadcast status Quote Link to comment Share on other sites More sharing options...
Bob F Posted March 20, 2004 Report Share Posted March 20, 2004 Ah, I thought mode 0 had to be read by ALL receivers. It's a basic necessity of the system, isn't it? A WAAS GPS is supposed to work with EGNOS and visa versa, but maybe they are saying some GPS's that are WAAS designed will not work in EGNOS for mode 0, only. And conversely, some EGNOS desgined GPS's will not work in WAAS for mode 0, only. When the system is fully up and transmitting in its' operational mode, all WAAS GPS's will work in EGNOS and vica versa. I think I read somewhere that the new Garmin GPS's work in WAAS or EGNOS no matter which mode is being transmitted. Anyway, Codfather and you were right, it appears they were transmitting in a different mode (0), but are now transmitting in mode 2. Either way, if you have a Garmin GPS, I think you should still be able to get a 3D differential signal (if your signal is not blocked by a house!!!). But I may be wrong. I'm learning new stuff about this all the time. What do you think? Are we a bunch of anoraks or what?? Bob F. Quote Link to comment Share on other sites More sharing options...
shytalk Posted March 20, 2004 Report Share Posted March 20, 2004 you will need to do some serious trailaway to get waas its for usa egnos is for europe Quote Link to comment Share on other sites More sharing options...
Bob F Posted March 20, 2004 Report Share Posted March 20, 2004 Yes, correct, but the beauty of it is that a US made GPS (like Garmin) which is designed for WAAS will work in Europe with the EGNOS system. If only the VHF units were as nicely compatible... Quote Link to comment Share on other sites More sharing options...
Paul D Posted March 20, 2004 Report Share Posted March 20, 2004 Maybe a bit petty Bob, but my Garmin was made in Taiwan !! I suspect pete was referring to my "faus pas" when I stated the WAAS signal was blocked by my house. ( It would be as the satellite is halfway around the other side if the world as well ) Of course I meant the EGNOS signal. Quote Link to comment Share on other sites More sharing options...
Paul D Posted March 20, 2004 Report Share Posted March 20, 2004 Another thought I have just had. My GPS shows a legend stating it is capturing the WAAS signal ( which is really the EGNOS signal ). Does a Garmin GPS bought in this country state that is capturing the EGNOS signal ( ie. WAAS replaced by EGNOS ) ? My money is on it stating WAAS still. Quote Link to comment Share on other sites More sharing options...
Coddy Posted March 21, 2004 Author Report Share Posted March 21, 2004 Hi My point is can we use this new information or is it best to use the standard GPS signals. I am fortunate in that I have still my old GPS unit installed so I suppose I can use both and see if they provide the coordinates. I will try that out on Sunday with the boat on the drive and report back. Thanks for the link Paul, I will keep am eye on it over the comming month Regards Cod Quote Link to comment Share on other sites More sharing options...
shytalk Posted March 21, 2004 Report Share Posted March 21, 2004 standard gps should be more than adequate for us there are very few who need or could tell they had better than 5m accuracythere main difference seems to be with differential the signal is more consistant ie gps should be accurate to 10m or better for 55 signals out of 60 the other 5 could be 20m+ accuracy as the signal are every second the shift in accuracy would be gone in the blink of an eye anyway also for fishing accuracy of better than a boats length is of no real benefit !!!! Quote Link to comment Share on other sites More sharing options...
Bob F Posted March 21, 2004 Report Share Posted March 21, 2004 Cod If you are receiving the differential EGNOS signal it should tell you the accuracy of the signal and any errors, so this should give you enough information to determine if it is usable or not. But, as I understand it, the Test signal cannot be relied on to always be there, so it might suddenly drop out. In that case, does the GPS automatically revert to the standard GPS satellites?? I don't know the answer to that one. Like you said, probably best to have an ordinary GPS backup operating in parallel, or if you only have an EGNOS enabled GPS, leaving it in normal GPS mode until the EGNOS system is fully operational. Bob F. Quote Link to comment Share on other sites More sharing options...
Coddy Posted March 21, 2004 Author Report Share Posted March 21, 2004 Did a check with the boat on the drive today. The EGNOS signal put the position of the boat 0.001 differance. This could be the receiver ariel being slightly to one side of each other. Another question? Do you guys leave the GPS or Chartpotters on Magnetic or True? If you use Admaral charts they give locations in True so what is the best way? Cod Quote Link to comment Share on other sites More sharing options...
Paul D Posted March 21, 2004 Report Share Posted March 21, 2004 In reply to Bob's question. You certainly do not need two GPS's ( one EGNOS enabled and one not ). On the Garmin, you can turn the WAAS ( EGNOS ) off. The only reason you would need/want to do this is when you know the WAAS/EGNOS signal is unavailable/intermittent. Turning off WAAS/EGNOS saves power as when turned on the GPS continues searching for the signal. If the WAAS/EGNOS signal is lost then the GPS reverts to "standard GPS" anyhow. Good question re: Magnetic or True. I have up to now only used a handheld GPS and havent used this to determine my heading. Personally, I think I will use Mag heading so that the GPS will match my compass, unless someone comes up with a good reason why you would not want to do this. Quote Link to comment Share on other sites More sharing options...
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