After three years of field use, this project's Arduino software has not needed any modification. The membrane keypad failed quickly, and was replaced with an identically faced click-buttton type which has performed faultlessly:-

https://www.ebay.com.au/itm/4-x-4-Matrix-Array-16-Keys-4-4-Switch-Keypad-Keyboard-Module-for-Arduino/282610223614?hash=item41cce1c9fe:g:YAkAAOSwi2lZkS3X

Some features of the accompanying Excel based spreadsheet were found to be unnecessary, and the main function of converting the SD data from the Arduino into Garmin POI files was the mostly used function.

The original Excel spreadsheet was not released with this project and I am now preparing a version suitable for public release, which will enable the primary function of
preparing Garmin POI files from the SD data produced y the GPS.