Looking at the FAQ (https://github.com/google/open-location-code/wiki/Evaluation-of-Location-Encoding-Systems#maidenhead-locator-system-mls https://github.com/g

Looking at the FAQ (https://github.com/google/open-location-code/wiki/Evaluation-of-Location-Encoding-Systems#maidenhead-locator-system-mls https://github.com/google/open-location-code/wiki/Evaluation...), it appears that Plus Codes are very similar to the Maidenhead codes, except in these respects: - Maidenhead codes contain vowels, which the Plus code designers didn't want to use in order to avoid having codes spell words (which might have negative associations or be profane). - The addition of the "+" character is felt to make it easier to autodetect addresses when provided to Google Maps or similar systems.