Database Accuracy
No doubt there are things that I don't understand well enough about how the database works, that define some of the problems and which Datum is which, which could affect it. The software is V2.12, the land database V2.0 and the last update was Nov 2002 - so I think it's as current as it reasonably can be - due for an aviation update soon (CAA chart + 6 mnths = August).
I flew over Portsmouth this morning, (Fairoaks - Sandown and back) and whilst the ground features are not spot on (and I am sure the comment about Jeppesen's interest in this is pretty accurate and the main reason for what I observe) for a less than £400 piece of kit, it is good enough for secondary naviational use and (what I used it for this morning - in conjunction with a map and a calculated VFR plan) accurate track keeping whilst dodging round the showers and in and out of bits of low clag. It also agreed with the aeroplanes VOR/DME kit as to where MID was and EGHN was totally accurate, my landing and take-off were straight down the little line of the symbol.
Interestingly the A3M / M27 junction wasn't too accurately represented - by 1/2 mile or so) and I put an extra waypoint in for Ryde from the Pooley's GPS companion which missed the "Ryde" in the Jepp database by about 0.4 mile and the "Pooley's" Ryde brought me nearer the pier than the Jepp one.
All in all my view is that it is just inaccuracies in the land database as it is not uniformly out of kilter and the EPE doesn't affect it much with varying satelite coverage either.
Jeppeson/Garmin ....... 8/10 - could try harder.