Editing Maidenhead Locator System (section)

==Adoption and use==
Like the QRA system before it, Maidenhead locators were enthusiastically adopted by radio amateurs beyond contesting, and it is now in widespread use.

Maidenhead locators are still used as part of the formulas for scoring in many [[VHF]] amateur radio contests and as the basis of earning awards like the American Radio Relay League's [[VHF/UHF Century Club]], URE TTLOC, etc. operating contests.

Under [[International Amateur Radio Union|IARU]] Region&nbsp;1 rules, VHF distance calculations are carried out between Maidenhead subsquare centres, assuming a ''spherical'' Earth. This results in a small error in distance, but makes calculations simpler and, given the inherent imprecision in the input data used, it is not the biggest error source.
Until the adoption of [[WGS 84]] as the official [[geodetic datum]] of the Maidenhead locator system in 1999,<ref name=QRZ.RU-Locator_System/> operators had usually specified their location based on their local national datum. Consequently, stations very near the edges of squares (at denoted precision) may have changed their locators when changing over to the use of WGS&nbsp;84.

The relatively new [[WSJT (amateur radio software)#FT8|FT8]] narrowband digital mode transmits Maidenhead locator square as part of standard messages, with the 4&nbsp;character locator square being efficiently represented within 15&nbsp;bits of the transmitted string.

In 2019{{Citation needed|date=September 2023}} the [[International Amateur Radio Union|IARU]] clarified the latest position on use of the IARU locator at various levels of precision, including a fifth pair of characters and that all letters should be uppercase.<ref>
{{cite conference
 |first=Andy, G4JNT |last=Talbot
 |date=16–23 September 2017
 |chapter=Clarification and extension of the IARU locator system
 |pages=42–45, 33–34
 |id=Appendix A, paper LA17 C5 17
 |editor-first=Dennis, ZS4BS |editor-last=Green
 |title=Report of the 24th IARU Region&nbsp;1 General Conference
 |conference=24th IARU Region&nbsp;1 General Conference
 |place=Landshut, DE
 |publisher=[[International Amateur Radio Union]] Region&nbsp;1
 |url=https://www.iaru-r1.org/wp-content/uploads/2019/12/GC_2017_Landshut_-Conf-Rep.pdf
 |access-date=19 September 2020
}}
</ref>