calculate.txt

(From https://www.dxzone.com/grid-square-locator-system-explained/)


Field Calculation

The world is divided into a 18×18 fields, measuring 20°x10°.  The first
operation is to add to longitude, 180° in order to work with positive numbers,
since we need to determine a non-negative number. Afterward we will divide the
reuslt by 20 (degrees) and we will consider the integer number obtained and its
remainder.  The letter, will correspond to the obtained number. Same
calculation but adding 90 (degrees) and dividing by 10 times for Latitude.

 A B C D E F G H I J K  L  M  N  O  P  Q  R
 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Longitude: 18.388544 degrees
= 18.388 + 180
= 198.388
= 198.388 / 20
= 9 + remainder 18.388
= J (location in 10th zone)

Latitude : -33.931833 degrees
= -33.931833 + 90
= 56.068167
= 56.068167 / 10
= 5 remainder 6.068167
= F (location in 6th zone)

Resulting Field is: JF


Square Calculation

We know that each Field is divided into 10×10 squares, measuring 2° x 1° each.
We will consider the remainders of previous Field calculation.

Longitude = 18.388
= 18.388 / 2
= 9 remainder (0.388)
= 9 (location in 9th zone)

Latitude = 6.068167
= 6.068167 / 1
= 6 remainder (0.68167)
= 6 location (location in 6th zone)

Resulting Square is: 96


Sub-Square calculation

Each sub-square is divided into 24×24 sub-squares, measuring 5 minutes
(0.083333 degrees) x2.5 minute (0.0416665 degrees).

The letter, will be the corresponding number.

 A B C D E F G H I J K  L  M  N  O  P  Q  R  S  T  U  V  W  X
 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Longitude = 0.388
= 0.388 : 0.083333
= 4 remainder 0,097
= E (location in 5th zone)

Latitude = 0.68167
= 0.68167 / 0.0416
= 1 remainder 0.638
= B (location in 2nd zone)

Resulting Sub-Square: EB