https://en.wikipedia.org/wiki/Maidenhead_Locator_System https://en.wikipedia.org/wiki/Maidenhead_Locator_System this is widely in use in the ham radio circle a

https://en.wikipedia.org/wiki/Maidenhead_Locator_System https://en.wikipedia.org/wiki/Maidenhead_Locator_System this is widely in use in the ham radio circle and it works great--if you know phonetic alphabets, it's easily understood over the air, truncation is well-behaved, and so on and so forth. edit: for SAR you probably need 8 characters not the customary 4/6 character version