There was a card trick that has always intrigued me. Called spell the cards. You separate out any suit of cards you like. Arrange them in a special order then. Remove a card from the top placing it on the bottom and say,"A", then another card from the top and put it on the bottom, say "C" then repeat say "E" and flip the top card laying it face down on the table and it is the "ACE". (or ONE works). Repeat this spelling all the cards through Q-U-E-E-N and the king is left.
Well this is an abbreviated version of that. Use the cards Ace to 10. Arrange the cards in that special order, WHICH YOU MUST DISCOVER. When the cards are arranged properly the first card is to be "A", and the second "B", the third "C" and so on. In this case 10 will be treated as if it is a zero.
Then the coordinates are North AI:DE.GHH West BE:HA.FHF