Crack the Code


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Image shared by John Martin CCby2.0 


The activity takes learning outdoors to uncover a series of geocaches each of which contains a cipher to decode and perhaps a small treat with instructions to find the location of the next geocache.

Suitable for:  KS2

What you need:

A Mobile GPS device such as the Garmin. Or a iPhone or iPad with 3G and a geocaching app installed.

A selection of coded messages for pupils to decode and solve. Each message reveals a set of coordinates for the next location.  Waterproof containers (caches) to store the messages. The final cache includes a certificate or reward.

What you do: 

Explain to your pupils that they are about to decipher a secret message which has been hidden around the school grounds.  Ideally, they should work in groups of 3 or 4.  Depending on numbers, it might be sensible to create a number of different trails.  Each group must collect 5 hidden caches and use their GPS receiver to move from one cache to another inputting the coordinates of the next location each time they find a cache.  The coded messages must be deciphered in order to receive hints as to the next location. The final cache may include a certificate or reward.


Explore the school grounds to find suitable locations to store each of the caches.  Ideally, these will be hidden from view and a little challenging to find; they could even be camouflaged.  Locate the co-ordinates of each location and record these.  Prepare  the caches to include a coded message which can be deciphered to reveal a location hint and the co-ordinates of the next cache. You could use a a range of coding techniques:

Here are some examples of codes:

Learning benefits:  

Pupils will understand more about encryption and coding and learn to relate this to the computing curriculum.  They will work in teams and learn how to collaborate, listen and respect the views of others.

Taking it further:

Geocache trails may be linked to key computer scientists in history, giving opportunities to refine their research skills and to validate their findings.  More complex codes such as binary, hex, and ascii could increase the challenge for more able learners.

Useful links:

Geo-caching guide from the National Trust

Background to the Enigma Machine and World War 2 codebreakers




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