The format is as described in ICAO Doc 8126 section 5.5.2 bullet d):
In the indication of the geographical coordinates of
a location:
- the latitude should be given first;
- symbols for degrees, minutes or seconds should
be omitted;
- two digits should always be used in expressing
values of less than 10 degrees of latitude; and
- three digits should always be used in expressing
values of less than 100 degrees of longitude.
For example, 050735N 0652542W means five
degrees, seven minutes and thirty-five seconds
North, sixty-five degrees, twenty-five minutes and
forty-two seconds West.
What is typical in AIP pubblications is the additional part
of decimal seconds, like 554718.23N.
Details
This format is used in AIP pubblications, for examples for runway threshold
coordinates, stand positions, etc.
This is used also in ALL_FT+ files from NM.
See also
Other coordinates:
ddm2dd(),
dms2dd(),
parse_lon_icao()