Maidenhead Subgrid Parameters, Paul Goble (ND2X/5)

Maidenhead Grids is an alternative system for expression of position on the earth. Paul discusses the system and how to convert between Maidenhead and longitude/latitude coordinates.


 
Introduction:

Each 4-digit, 1 degree in latitude X 2 degrees in longitude, maidenhead grid division is divided into 24 X 24 = 576 6-digit subgrids. Each subgrid is 2.5 minutes in latitude X 5 minutes in longitude.

Whereas the distances represented by these lat-lon divisions are fairly constant for the latitude dimension, the longitude distances vary with latitude. As an example, the southern edge of EL16 (26 deg N lat) is 124.4 miles (200.2 km) across, while the northern edge of EN18 (49 deg N lat) is 90.9 miles (146.3 km). This affects the diagonal distances, of course, as well.

The table below shows the variation in grid and subgrid width as well as in the diagonal distances across each.


To download an exellent program to convert between lat-lon and maidenhead grids, and to calculate bearing (including reverse) and distance in miles or kilometers, go to the W4SM site; scroll down to and select "New Improved" WinGrid Ver4.1 (wingrid.exe).


Grid Latitude (deg N) Grid width (mi / km) Subgrid width (mi / km) Grid diagonal (mi / km) Subgrid diag. (mi / km)
(  )L06 26 to 27 124.4 / 200.2 5.18 / 8.34 141.7 / 228.1 5.9 / 9.5
(  )L07 27 to 28 123.3 / 198.5 5.14 / 8.27 140.8 / 226.5 5.87 / 9.44
(  )L08 28 to 29 122.2 / 196.7 5.09 / 8.2 139.8 / 225 5.83 / 9.38
(  )L09 29 to 30 121.1 / 194.8 5.04 / 8.12 138.8 / 223.3 5.78 / 9.3
(  )M00 30 to 31 119.9 / 192.9 5 / 8.04 137.7 / 221.7 5.74 / 9.24
(  )M01 31 to 32 118.7 / 191 4.95 / 7.96 136.7 / 219.9 5.7 / 9.16
(  )M02 32 to 33 117.4 / 188.9 4.89 / 7.87 135.6 / 218.2 5.65 / 9.09
(  )M03 33 to 34 116.1 / 186.9 4.84 / 7.79 134.5 / 216.4 5.6 / 9.02
(  )M04 34 to 35 114.8 / 184.7 4.78 / 7.7 133.3 / 214.5 5.55 / 8.94
(  )M05 35 to 36 113.4 / 182.5 4.73 / 7.6 132.1 / 212.6 5.5 / 8.86
(  )M06 36 to 37 112 / 180.3 4.67 / 7.51 130.9 / 210.7 5.45 / 8.78
(  )M07 37 to 38 110.6 / 178 4.61 / 7.42 129.7 / 208.7 5.4 / 8.7
(  )M08 38 to 39 109.1 / 175.6 4.55 / 7.32 128.5 / 206.7 5.35 / 8.61
(  )M09 39 to 40 107.6 / 173.2 4.48 / 7.22 127.2 / 204.7 5.3 / 8.53
(  )N00 40 to 41 106.1 / 170.7 4.42 / 7.1 125.9 / 202.6 5.25 / 8.44
(  )N01 41 to 42 104.5 / 168.2 4.35 / 7.01 124.6 / 200.5 5.19 / 8.35
(  )N02 42 to 43 102.9 / 165.6 4.29 / 6.9 123.3 / 198.4 5.14 / 8.27
(  )N03 43 to 44 101.3 / 163 4.22 / 6.79 121.9 / 196.2 5.08 / 8.18
(  )N04 44 to 45 99.6 / 160.4 4.15 / 6.68 120.5 / 194 5.02 / 8.08
(  )N05 45 to 46 97.9 / 157.6 4.08 / 6.57 119.1 / 191.7 4.96 / 7.99
(  )N06 46 to 47 96.2 / 154.9 4.01 / 6.45 117.7 / 189.5 4.9 / 7.9
(  )N07 47 to 48 94.5 / 152 3.94 / 6.33 116.3 / 187.2 4.85 / 7.8
(  )N08 48 to 49 92.7 / 149.2 3.86 / 6.22 114.9 / 184.9 4.79 / 7.7
(  )N09 49 to 50 90.9 / 146.3 3.79 / 6.1 113.5 / 182.6 4.73 / 7.61

Calculations are not +/- 1%, but they are close. The distances showing two digits after the decimal point should most likely be rounded off, e.g. call "5.18" 5.2, "5.14" 5.1, etc.

Note for 25 to 59 degrees latitude:

Designators and calculated distances are for subgrids from EL16 northward through EM17 to EN18. Dimensions are same for DL16, DM17 and DN18, as well as CL16, CM17 and CN18 or FL16, FM17 and FN18, etc., respectively.
 
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