Regex Editor & Tester

This regular expression matches strings containing one to three uppercase letters from the set N, E, O, and S. It is specifically designed to validate abbreviations for French compass directions, where 'O' represents West (Ouest) instead of 'W'. It is useful for parsing or validating geographical directional inputs like N (Nord), NE (Nord-Est), or SSE (Sud-Sud-Est) on a line-by-line basis.