The message <[email hidden]>
from Martin Rand <[email hidden]> contains these words:
Quoted message said:Quoted message said:Now that we have easy access to GPSRs which can supply grid refs as an estimate to a one metre
"point" (ok, square if you like) plus several metres probable error, the OS convention is
somewhat incovenient and out-dated.
Quoted message said:Not if you're doing biological distribution mapping, it isn't. Whatever precision a grid ref of a
locality is quoted to, it refers to the SW corner of the square at that precision. Apart from the
fact that a change would invalidate the millions of existing records held across many systems, it
would be _less_ convenient, because more difficult to relate easily by sight to the area on a
gridded map. (And even require slightly more mental arithmetic to correlate to a GPS reading.)
You are barking up the wrong tree. GPS references are true co-ordinates unlike the American*
convention belatedly adopted by our OS. (Someone, Dominic possibly, has previously confirmed that
GPS references are rounded, not truncated).
The original system which the OS misguidedly junked could be used to define a square as well as a
point by the simple expedient of clearly stating that the reference was for a square.
Meanwhile those not 'in the know' will continue to take the instructions on a map to make a grid
reference a point at face value while most of the rest of us will continue to treat it as a point
for practical reasons.
On the example used above I can't see that using real co-ordinates would make the slightest bit of
difference. The point quoted is still the SW corner of the grid square and all that would be
necessary would be to
*Yes, I don't actually know that it is the Americans fault but it seems likely that when the
Americans reinvented (borrowed,stole, call it what you will) our system they missed the important
bit that the default reference was a point and took the occasional references to a square as
reinforcing their misunderstanding.
Completely OT (but relevant to the above paragraph) a recent C4 documentary on the sound barrier
highlighted a similar misunderstanding. When the Yanks were given access to the British supersonic
project (M52 IIRC) they tookaway detailed plans which included the key to control though the sound
barrier, the moving tailplane. When the came to build their rocket engined imitation (their jet
engines weren't up to the task at the time) the significance of the moving tailplane was overlooked
and it ended up as a tailplane with adjustable attitude, but not, in its original form, adjustable
in flight.
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Roger Looking North over the Aire Valley (and Marley Gasworks) to Rombolds Moor Top Posters
killfiled on sight