I have a very good experience with Garmin eTrex Legend HCx –
here and here they write that HCx has a very sensitive chip, that works in forest, deep valleys and in cities – and I can only confirm – with HCx I was able to get my position in plane!
How sensitive is eTrex 30, related to HCx? Have you been able to catch satellites in room / plane / in a narrow street? eTrex 30 doesn't say to be that sensitive at garmin website.
(Could HCx then be more precise/usable in these conditions despite eTrex 30 supporting GLONASS?)
Best Answer
I guess it depends where you are located, as the precision of the etrex 30 will depend on how many satellites (GPS and Glonass) you can see. As far as I know (but I might be wrong), the Glonass constellation is not so dense over northern America, but better in Asia and Europe.
From my experience the sensitivity of the etrex30 is much much better than the one of the Legend. In the house where I am now, I get an (horizontal) accuracy of less than 10 meters. Outside, I almost always have 3-5 meters. In cities, with narrow streets, I haven't ever lost a signal so far, same in a forest. Haven't tried in a plane yet.
Also, the battery seems to last much longer than the Legend . Finally, it doesn't have the rubber problem of the etrex Legend.
I do not work for Garmin, but I would warmly recommend this one!
Hope that helps!