A tetrad is an area 2 km x 2 km square. The term refers to any of the 25 such squares which make up a standard hectad.
The term comes from the Greek word tetras meaning "four".
Tetrads are sometimes used by biologists for reporting the distribution of species to maintain a degree of confidentiality about their data, though the system is not in universal use.
The tetrads are labelled from A to Z (omitting O) according to the "DINTY" system as shown in the grid below, which takes its name from the letters of the second line.
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
- ^ "DINTY Tetrads". Kent and Medway Biological Records Centre. Archived from the original on 27 May 2011. Retrieved 23 December 2008.
- "Collins English Dictionary". Retrieved 9 February 2024.
- "National Grid References". Sussex Biodiversity Record Centre. 2008. Retrieved 23 December 2008.
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