[OSM-talk] Choice of GPS for bicycle use in London

[Richard Fairhurst]

Nick W wrote:

> I've found the eTrex Legend passably accurate in most scenarios. It's
> better in rural than urban areas, but even still I have mapped large
> numbers of streets in residential parts of Southampton and the maps do
> seem to correspond passably well to reality. That said, I have done little
> if any mapping in city *centre* areas.

IMX the eTrex is as good as you could wish for in housing estates and  
other suburban areas.

In city centres, as has been suggested, it has much more trouble. It  
performs very badly on the sort of mapping expedition where you're  
walking/cycling around from city centre street to city centre street,  
making frequent turns. (That's not just concrete canyons - I got  
pretty lousy results doing just that in picturesque, low-rise Ludlow  
at the weekend.)

But...

If you drive along the same streets as part of a "through journey" -  
in other words, in one side, across the city centre, and out again -  
it seems to perform much better. We got a fairly decent track of the  
A44 through Worcester yesterday, even though cycling the same route a  
few weeks ago had produced less than brilliant results.

This makes me suspect that there are two problems with the eTrex in  
city centres:

1. The 'track simplification' algorithm (i.e. record more points  
around corners)
2. Poor initial acquisition time, especially to a decent level of  
accuracy, in areas of reduced visibility (narrow streets/concrete  
canyons)

I would be interested to learn from anyone with configurable tracklog  
recording (as per the Geko, and perhaps the more expensive eTrexs?)  
whether setting it to "every 5 seconds", or so, improves the results.

cheers
Richard