Onshore licence coordinates are defined using the National Grid referencing system, which is a metric grid on a Transverse Mercator projection.

National Grid coordinates are expressed as distances measured in metres east and north from the grid origin, which is located west of the Isles of Scilly. The National Grid defines a series of 100km squares, each of which is further subdivided into 10km squares. The 100km squares are identified by two letters, e.g. SE or TL. The 10km squares are identified by the letters of the 100km square within which they lie, plus a number from 00 to 99 as follows:

Onshore licence coordinates
09 19 29 39 49 59 69 79 89 99
08 18 28 38 48 58 68 78 88 98
07 17 27 37 47 57 67 77 87 97
06 16 26 36 46 56 66 76 86 96
05 15 25 35 45 55 65 75 85 95
04 14 24 34 44 54 64 74 84 94
03 13 23 33 43 53 63 73 83 93
02 12 22 32 42 52 62 72 82 92
01 11 21 31 41 51 61 71 81 91
00 10 20 30 40 50 60 70 80 90


Example: If this diagram showed the SE block, then square 46 would be referred to as SE46.

DESNZ refers to each 10km square as a block. A licence may cover a whole block, part of a block, or several blocks or part-blocks.

Map of the UKCS illustrating the relationship between the National Grid and quadrants

Map of the UKCS illustrating the relationship between the National Grid and quadrants

Ordnance Survey website offers further information on the National Grid. 

The system of quadrants and blocks used in offshore licensing does extend onshore, but we only use it for well numbering (see Petroleum Operations Notice 12 for details).