2 char OS GB grid conversion

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2. Travel & Local

A flow for people in mainland Great Britain to convert between the initial two letters of the normal Ordnance Survey Grid Reference and the numbers that start the all numeric Full Grid Reference. The latter being more normally used when converting to other grid reference systems such as Latitude and Longitude. It is not valid in the Orkneys or Shetland as the all number Full Grid there is of a different length, and I am not expecting to be there in the near future.

There are two potential starts to this flow, being different ways of creating the key conversion array. The active one has the reference data entered as a text string in a "Set variable" block the alternative (non active) part at the start was to load from a simple data file with each pair of characters entered on a separate line. It is no longer necessary but shows how I created the text now pasted into the "Set variable" bloc, which makes the flow more portable.

Produced by me to practice use of arrays etc. and prepare for a more complete coordinate transform package.