View source for ISO 6709

{{short description|International standard for representation of geographic location}}
{{One source|date=July 2020}}
{{Update|reason=was written before current (third) edition of the standard|date=May 2023}}
{{Geodesy}}

'''ISO 6709''', ''Standard representation of geographic point location by coordinates'', is an [[international standard]] for representation of [[latitude]], [[longitude]] and [[altitude]] for geographic point locations.

The first edition ({{Nowrap|'''ISO 6709:1983'''}}) was developed by [[ISO/IEC JTC 1]]/SC 32.  Later the standard was transferred to [[ISO/TC211]], ''Geographic information/Geomatics'' in 2001.  The committee completely revised the second edition ({{Nowrap|'''ISO 6709:2008'''}}). There was a short technical corrigendum ({{Nowrap|'''ISO 6709:2008/Cor 1:2009'''}}) released in 2009.<ref name="Corrigendum2009">{{cite web|title=ISO 6709:2008/Cor 1:2009 -|url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=53539|website=ISO|access-date=8 June 2016|archive-date=4 August 2016|archive-url=https://web.archive.org/web/20160804221255/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=53539|url-status=live}}</ref>
The third edition {{Nowrap|'''ISO 6709:2022'''}} was published in 2022.<ref>{{cite web |title=ISO 6709:2022 |url=https://www.iso.org/standard/75147.html |website=www.iso.org |access-date=26 May 2023 |language=en |archive-date=26 May 2023 |archive-url=https://web.archive.org/web/20230526125505/https://www.iso.org/standard/75147.html |url-status=live }}</ref>

The second edition consists of a main part and eight annexes (Annexes A through H).  The main part and Annexes A and C give encoding-independent general rules to define items to specify geographic point(s).  Annex D suggests a display style for human interface.  Annexes F and G suggest styles of [[XML]] expression.  Annex H suggests string expression, which supersedes the first edition of the standard.

== General rules ==

=== Items ===
A geographical point is specified by the following four items:
* First [[horizontal position]] coordinate (''Φ'' or ''y''), such as latitude (negative number south of equator and positive north of equator)
* Second horizontal coordinate (''λ'' or ''x''), such as longitude (negative values west of Prime Meridian and positive values east of Prime Meridian)
* [[Vertical coordinate]], i.e. height or depth (optional)
* Identification of [[coordinate reference system]] (CRS) (optional)

The first three items are numerical values called coordinates.  The CRS gives the relationship between the coordinates and a point on the earth. The identification of CRS could be a full description of properties defined in [[ISO 19111]]; only an identifier given by some registry (such as [[EPSG]]) is used in most cases, since only such identification is enough for most information exchange purposes.

=== Order, sign, and units ===
Order, positive direction, and units of coordinates are supposed to be defined by the CRS. When CRS identification is missing, the data must be interpreted by the following conventions:
* Latitude comes before longitude
* North latitude is positive
* East longitude is positive
* Fraction of degrees ([[decimal degrees]]) is preferred in digital data exchange, while [[sexagesimal]] notation is tolerated for compatibility

There is no such interpretation rule for vertical coordinates.

== Representation at the human interface (Annex D) ==
When there is no guideline given from the user community, the following styles are suggested:

# Coordinate values (latitude, longitude, and altitude) should be delimited by spaces.
# The decimal point is a part of the value, thus must usually be configured by the operating system.{{efn|Probably the intention is that the locale environment should not be overridden.}}
# Multiple locations should be represented by multiple lines.
# Latitude and longitude should be displayed by sexagesimal fractions (i.e. minutes and seconds).
# When minutes and seconds are less than ten, leading zeroes should be shown.
# Degree, minutes and seconds should be followed by the symbols ° ([[U+00B0]]), ′ ([[U+2032]]), and ″ ([[U+2033]]), without spaces between the number and symbol.
# North and south latitudes should be indicated by ''N'' and ''S'' following immediately after the digits.
# East and west longitudes should be indicated by ''E'' and ''W'' following immediately after the digits.
# Units of elevation or depth should be given by symbols, immediately after the digits.{{efn|This is different from SI style guides.{{disputed-inline|date=May 2023}}}}
# Elevation below [[zero-level reference]] or depth above reference level should be indicated by a minus sign − (U+2212).

Examples:
* 50°40′46″N 95°48′26″W 123.45m
* 50°03′46″S 125°48′26″E 978.90m

The standard does not specify how coordinates at the [[equator]], [[prime meridian]] or [[antimeridian]] should be written.

== XML representation (Annex F) ==
The XML representation based on the conceptual model of Annex C uses XML namespace http://www.isotc211.org/2006/gpl{{dead link|date=November 2017 |bot=InternetArchiveBot |fix-attempted=yes }}.  However, there is no published XML schema at the time of writing (August 2011).

<syntaxhighlight lang="xml">
<gpl:GPL_CoordinateTuple xmlns:gpl="http://www.isotc211.org/gpl">
  <gpl:tuple srsName="urn:ogc:def:crs:EPSG:6.6:4326">
    35.89421911 139.94637467
  </gpl:tuple>
</gpl:GPL_CoordinateTuple>
</syntaxhighlight>

== String expression (Annex H) ==
A string expression of a point consists of latitude, longitude, height or depth, CRS identifier, and trailing [[solidus (punctuation)|solidus]] (<code>/</code>) without any delimiting character.  When height or depth is used, there must be CRS identifier.{{efn|Height without CRS identifier was allowed in the first edition, but not today. Ending with longitude is still allowed.}}

=== Latitude ===
Latitude is a number preceded by a sign character.  A plus sign (<code>+</code>) denotes northern hemisphere or the equator, and a minus sign (<code>-</code>) denotes southern hemisphere.{{efn|Annex H allows letters <code>N</code> and <code>S</code> as sign characters, but gives no examples.}}

The integer part of the number is a fixed length. The number of digits in that part indicates the units, thus leading zero(es) must be filled when necessary. The fractional part must have the appropriate number of digits to represent the required precision of the coordinate.

{| class="wikitable"
|-----
! num. digits || units || format || example
|-----
| 2 || deg || ±DD.D || +40.20361
|-----
| 4 || deg, min || ±DDMM.M || +4012.22
|-----
| 6 || deg, min, sec || ±DDMMSS.S || +401213.1
|}

=== Longitude ===
Longitude is a number preceded by a sign character. A plus sign (<code>+</code>) denotes east longitude or the [[prime meridian]], and a minus sign (<code>-</code>) denotes west longitude or 180° meridian (opposite of the prime meridian).{{efn|Annex H allows letters <code>E</code> and <code>W</code> as sign characters, but gives no examples.}}

Rules about the number of digits are the same as for latitude.

{| class="wikitable"
|-----
! num. digits || units || format || example
|-----
| 3 || deg || ±DDD.D || -075.00417
|-----
| 5 || deg, min || ±DDDMM.M || -07500.25
|-----
| 7 || deg, min, sec || ±DDDMMSS.S || -0750015.1
|}

=== Height or depth ===
{{further|Vertical position}}

* When height or depth is present, CRS identifier must follow.
* Positive direction and units are defined by CRS.{{efn|This is different from the 1983 edition.}}
* Negative number does not necessarily mean position below reference level.
* Positive is up for height, down for depth.

=== CRS identifier ===
{{further information|SRID}}
The CRS identifier begins with "CRS".  There are three styles:

# When a registry provides online resolver, CRS<''url''>
# When a registry is offline, CRSr''egistry'':''crsid''
# When the data creator provides full definition of CRS using ISO 19111, CRS<''CRSID''>

The example of original Annex H always use "CRSWGS_84".

===Examples===
* [[Atlantic Ocean]] +00-025/
* [[France]] +46+002/
** [[Paris]] +48.52+002.20/
*** [[Eiffel Tower]] +48.8577+002.295/
* [[Mount Everest]] +27.5916+086.5640+8850CRSWGS_84/
* [[North Pole]] +90+000/
* [[Pacific Ocean]] +00-160/
* [[South Pole]] -90+000+2800CRSWGS_84/
* [[United States]] +38-097/
** [[New York City]] +40.75-074.00/
*** [[Statue of Liberty]] +40.6894-074.0447/

== See also ==
* [[List of geodesic-geocoding systems]]
* [[LOC record]]
* [[Geo (microformat)]]

== Notes ==
{{Notelist}}

== References ==
{{Reflist}}

==External links==

=== Standards ===
* [https://www.iso.org/standard/75147.html Catalogue entry for ISO 6709:2022 (Edition 3)]
* [https://web.archive.org/web/20111009145601/http://www.xyz.au.com/members/intelligence/pdf_files/ISO_FDIS_6709.pdf Final draft of ISO 6709:2008 (archived)]
* [http://www.w3.org/2005/Incubator/geo/Wiki/LatitudeLongitudeAltitude Profile by W3C GeoXG]

=== Implementations ===
* [https://github.com/sualeh/pointlocation6709 Point Location 6709 - an open-source Java parser and formatter] on GitHub
* [https://github.com/sualeh/pointlocation6709-js Point Location 6709 - an open-source JavaScript implementation] on GitHub
* [http://coordinate.codeplex.com C# Implementation] {{Webarchive|url=https://web.archive.org/web/20110820003848/http://coordinate.codeplex.com/ |date=2011-08-20 }} at Codeplex
* [https://github.com/TechSmith/ISO6709Location-objc Objective-C Implementation] on GitHub

{{ISO standards}}

[[Category:ISO standards|#06709]]
[[Category:Geographic coordinate systems]]
[[Category:ISO/TC 211]]