"Graculus" wrote in message
...
(No, GPS isn't accurate enough to say if its on the up fast/down slow/etc
track.)
Should be - I get accuracy down to about a metre on a very old hand-held GPS
box. It's certainly good enough to work out the difference at Clapham
Junction because 12-car trains don't get held up when they call on the fast
line platforms, and I've seen it work correctly when a 12-car gets diverted
to the slow platforms. The SDO system just reverts to plan B if it finds
itself somewhere (like the SN platforms at Victoria) where the GPS isn't
good enough.

ISTR reading somewhere that the 377s going to the FCC route are having their
SDO modified to allow for better running between Blackfriars and Kentish
Town.

D A Stocks