Experiences in Eurostar with GR230 vs Garmin eMap

Hamie · Regular Visitor Joined: Dec 30, 2003 Posts: 177

On the weekend I went to Disneyland Paris on Eurostar (Out of Waterloo) and took along my new GR230 and my old eMap.

The eMap hadn't been used since I cam back to the UK from New Zealand in November, the GR230 had been used a couple of days earlier in my car & (Should) have had a full almanac & current location (Within 50km).

Leaving Waterloo I placed the GR230 in the window of the carriage and ran up some software on my laptop to watch the GPS status. The GPS was running in SiRF mode @9600bps and spent the next 30 or so minutes continually trying to get a position fix, but was unable to get on until just before Ashford terminal. About 2 minutes before we pulled into Ashford, I suddenly got a 4+ satellite position. This was of course lost for a short whole at Ashford (While the sky was obscured by the station) and then lost completely when we entered the chunnel.

After leaving the chunnel the GPS again wandered around hunting for sats before finally getting a fix once more about half way between Calais and Arras. The GPS fix was patchy between there and half way between Arras & Paris before suddenly dropping the connection completely and never regained it.

This all had me wondering at first if the Eurostar was (Like the TGV apparently is) incapable of recieving GPS signals in the carriages because of metallic coatings on the windows.

However...

In comparison, I finally whipped out my eMap about 5 minutes before Ashford and turned it on for my daughter to watch. After a couple of minutes it realised we weren't in NZ (No sats) and asked whether to keep searching, init from the map or us eindoors. I used the map to tell it we were somewhere within reach of London and it got a lock within 2-3 minutes. The eMap then kept the signal, almost with fail (Except of course in tunnels) all the way to Disney (Marne-La-Valle - Chessey).

On the way back it was pretty much similiar. The GR230 didn't get lock out of MLV-C until almost at Arras. It kept it for about 5 minutes, got it again just before Calais, lost it in the Chunnel and never regained it again. I didn't use the eMap until about Vauxhall (Last station before Waterloo?) and it didn't get a lock then either, but it was a little hopeful about that one).

All in all, I was a little disappointed about the GR230's performance. I didn't see any noticiable improvement between the Pretec CF GPS which uses an older SiRF chipset and the IIe/LP that ythe GR230 apparently uses. Nor did the later (2.3 vs 2.2) firmware make a great deal of difference for the newer unit.

I can't blame window coatings for bad performance as the eMap appeared to have no problems with getting & keeping a lock at 300km/hour within the carriage, despite last being used in Tauranga, NZ at the beginning of November).

YMMV...

Hamish.

lbendlin · Posted: Wed Jan 21, 2004 2:56 pm Post subject:

Thanks for the interesting observations. I think it is still related to the window coating - the german ICE is known to cause the same problems, and the TGV is probably the same. Maybe the antenna types are different . What is the sat ratio when you compare the two devices in clear sky view?
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Skippy · Posted: Wed Jan 21, 2004 6:39 pm Post subject:

Hamie · Regular Visitor Joined: Dec 30, 2003 Posts: 177

Skippy · Posted: Thu Jan 22, 2004 5:32 pm Post subject:

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