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Tetrads
(2km x 2km squares) are referred to by a tetrad-letter. This avoids
confusion with 1-km squares. The notation used commonly by most
biodiversity recorders, is the EJPUZ-DINTY notation (see diagram to see
why it’s called that).
In
Hampshire, all tetrads have a format of SUnnX (or SZn9X along the
coast),
where
SUnn is the 10-km square reference, and X is the tetrad letter.
In the
diagram below, imagine the whole box is a 10-km square. The tetrads are
given letters A, B, C, etc starting from bottom left & moving up. We
leave out letter “O” so as to avoid confusion with zero, and to leave us
with 25 letters. The first two rows now read EJPUZ-DINTY !
So, if
the 10-km square were (say) SU63,
then
tetrad SU63R for example would be the 2km x 2km square with its bottom
left-hand corner at 6-figure gridref SU 660 320.
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