Decimal degrees

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Decimal degrees (DD) is a notation for expressing latitude and longitude geographic coordinates as decimal fractions of a degree. DD are used in many geographic information systems (GIS), web mapping applications such as OpenStreetMap, and GPS devices. Decimal degrees are an alternative to using degrees-minutes-seconds (DMS) notation. As with latitude and longitude, the values are bounded by ±90° and ±180° respectively.

Positive latitudes are north of the equator, negative latitudes are south of the equator. Positive longitudes are east of the Prime Meridian; negative longitudes are west of the Prime Meridian. Latitude and longitude are usually expressed in that sequence, latitude before longitude. The abbreviation [dLL] has been used in the scientific literature with locations in texts being identified as a tuple within square brackets, for example [54.5798,-3.5820]. The appropriate decimal places are used,^[1] negative values are given using a hyphen-minus character.^[2] The designation of a location as, for example [54.1855,-2.9857] means that it is potentially computer searchable and that it can be located by a generally (open) referencing system such as Google Earth or OpenStreetMap. The location [54.1855,-2.9857] is that of a 2023 piece of land art 'Out of the ground, a thread of air' by Julie Brook. Four decimal places is usually sufficient for most locations, although for some sites, for example surface exposure dating, five or even six decimal places should be used.

The [dLL] format can be used within publications to specify points or features of interest and within remote sensing to identify ground truth locations within Digital Earth and complying within the FAIR data principles. The format can also be used as a starting point for a traverse or transect.^[3] The American Geophysical Union (AGU) 'Landslides Blog' ^[4] by David Petley uses this georeferencing system. With the increase in scientific papers needing to be searched for words, terms, phrases, authors and data, the [dLL] format can be used to link terms to author name (and by orcid), place-label location and journal or publication.^[5]