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.[1]
The term comes from the Greek word tetras meaning "four".[2]
Tetrads are sometimes used by biologists for reporting the distribution of species to maintain a degree of confidentiality about their data,[3] though the system is not in universal use.[1]
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.[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]
- ^ a b c "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.