ISO 6709:1983 "Standard representation of latitude, longitude and altitude
for geographic point locations" a format designed for usage in human
readable compact file formats, protocols, etc. The standard allows
both a minute/second representation as well as a decimal fraction
representation.

Latitude can be represented as

  DD.DD          degrees and decimal degrees
  DDMM.MMM       degrees, minutes and decimal minutes
  DDMMSS.SS      degrees, minutes, seconds and decimal seconds

Prefix with + north of and on equator, and with - south of equator.

Likewise, longitude can be represented as

  DDD.DD          degrees and decimal degrees
  DDDMM.MMM       degrees, minutes, and decimal minutes
  DDDMMSS.SS      degrees, minutes, seconds, and decimal seconds

Prefix with + east of and on prime meridian (Greenwich), and with -
west of Greenwich up to the 180th meridian.

Leading zeros are required for latitude and longitude.

Optionally, append altitude in meters (prefix with + above and on the
geodetic reference datum and with - below it).

If a termination character is needed in the format, / is recommended.

Examples:

  +40-075/
  +401213.1-0750015.1+2.79/
  +40.20361-075.00417/