Is it just me, or has the server gone and mixed up the order of the posts, and given my answer before Iain had finished answering the question?
Monocock, you are quite right in pointing out that 610m is 2001'. However, you failed to notice that the ISA temperature at 3000' is actually 9 degrees, not 11 degrees!
So - second attempt. The actual temperature is ISA minus 19 degrees, so the correction to the altitude of 3001' is 7.6%. 3001' plus 7.6% is 3229'.
FFF
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PS - Yes, I'm bored.
PPS - Yes, I did have to look up the temperature correction formula!
But that only shows just how bored I am!
PPPS - Happy Birthday, Monocock!