Tetrad (area)

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A tetrad is an area 2 km x 2 km square. The term has a particular use in connection with the British Ordnance Survey national grid, and then refers to any of the 25 such squares which make up a standard hectad.[1]

Tetrads are sometimes used by biologists for reporting the distribution of species to maintain a degree of confidentiality about their data,[2] though the system is not in universal use.[1]

The tetrads are labelled from A to Z (omitting O) according the "DINTY" system as shown in the grid below, which takes its name from the letters of the second line.[1]

E J P U Z
D I N T Y
C H M S X
B G L R W
A F K Q V

References[edit]

  1. ^ a b c "DINTY Tetrads". Kent and Medway Biological Records Centre. Retrieved 23 December 2008. 
  2. ^ "National Grid References". Sussex Biodiversity Record Centre. 2008. Retrieved 23 December 2008.