I like real maps, but mobile phones can be vital in an emergency

‘A phone screen is too small to see the wider terrain,’ writes Joe Oldaker. Photograph: Alamy

Having rambled for 65 years with Ordnance Survey maps and a compass, I agree with John Harris about using GPS in the wild (We now leave navigation to our phones. The result: more of us are getting hopelessly lost, 27 April). A phone screen is too small to see the wider terrain. But having carried an emergency whistle and pocket heliograph, I have to admit that phones can be a lifesaver in a real emergency.
Joe Oldaker
Nuneaton, Warwickshire

• I can’t be the only one to think that if you can afford to quaff champagne on a regular basis, that would tend to lead to a more positive outlook and greater life chances generally (Drinking champagne could reduce risk of sudden cardiac arrest, study suggests, 29 April).
Deirdre Burrell
Mortimer, Berkshire