Kirsty,
I would have thought most pilots would have assumed i meant ground speed, and not IAS, as flying into a 30Kn head wind at 90Kn would OBVIOUSLY make a big impact on your Actual time of arrival! So if you have flown say 100 miles to your IP, then you would have an accurate estimation of the prevailing weather conditions, wind included! This is why you only fly the last twenty minutes to your target with reference mainly on your numbers. I also said mark off your chart at 5 mile intervals, and see what is there and cross check that with your map and watch. Trust me it works!
""If I'm flying down the VFR corridor from The Isle of Wight to Cherbourg, I'll have a good 45 mins in the air to assess what direction the wind is blowing from and how it's impacting my ground speeding and heading. So far everytime I've managed to pitch up in France within 5 mins of my estimate and within half a mile of my intended track! "" So you have proved my point! What were you using to navigate accross the sea? I suspect time and heading were much more use than ground features! Or a GPS
Darth Bovine, the reason his gps showed bad info was user error, i n as much as he had the wrong datum for this side of the world! This would probably not have happened had he had training in the correct use of GPS, hence the need for proper training in its safe use!