Solving a geocache puzzle

A puzzle or multi cache hides its final position behind clues: letters to count, a code to break, a formula such as N 51° 2A.B(C+1) to fill in. These tools cover the usual steps. For a cipher you can’t recognise, start with Solving an unknown cipher.

1. Decode the clues

Most clues turn words into numbers, or hide words in a code:

• Letter values: Number Codes gives A1Z26 (A = 1, B = 2 …), the tap code, phone keypad presses and more, and decodes them back.
• Dots and dashes, written down or in a sound file: Morse Code reads both, and can listen to a recording.
• A keyword or a substitution: Classical Ciphers has Vigenère, Atbash, Playfair, Pigpen and over twenty others, with the key fields each one needs.

2. Work out the formula

Put the numbers in Values in Geocache Formulas, as A=3 B=7 or one a line, then paste the formula from the listing. Brackets are worked out first, the N, S, E and W are read as compass letters, and you get the position in degrees and minutes and in decimal degrees, plus each bracket’s value and the digit sum many checkers ask for.

Check the result has the right number of digits: if A is 12, 2A becomes 212. The tool warns about a bracket that isn’t a whole number, which usually means a value is wrong.

3. Convert the position

Listings use degrees and decimal minutes (N 51° 30.044 W 000° 07.478); a GPS or map may want decimal degrees, an Ordnance Survey grid reference or a Plus Code. Paste the position into the Coordinate Converter to get every form, with links to open it in a map.

4. Sanity-check it

Most puzzle caches must be within a couple of miles of the published position. Put the published position and your answer into Distance & Bearing: if it’s 400 km away, a value is wrong. For a multi cache that says “walk 250 m on a bearing of 70°”, give the start, the bearing and the distance to project the next waypoint.