ISO 6709

Key takeaways

ISO 6709 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect ISO 6709 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of ISO 6709 from memory before moving on to harder problems.

Reference excerpt

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 (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 (ISO 6709:2008). There was a short technical corrigendum (ISO 6709:2008/Cor 1:2009) released in 2009. The third edition ISO 6709:2022 was published in 2022. 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. 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. 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. However, there is no published XML schema at the time of writing (August 2011).

String expression (Annex H) A string expression of a point consists of latitude, longitude, height or depth, CRS identifier, and trailing solidus (/) without any delimiting character. When height or depth is used, there must be CRS identifier.

Latitude Latitude is a number preceded by a sign character. A plus sign (+) denotes northern hemisphere or the equator, and a minus sign (-) denotes southern hemisphere. 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.

Longitude Longitude is a number preceded by a sign character. A plus sign (+) denotes east longitude or the prime meridian, and a minus sign (-) denotes west longitude or 180° meridian (opposite of the prime meridian). Rules about the number of digits are the same as for latitude.

Height or depth

When height or depth is present, CRS identifier must follow. Positive direction and units are defined by CRS. Negative number does not necessarily mean position below reference level. Positive is up for height, down for depth.

CRS identifier

The CRS identifier begins with "CRS". There are three styles:

When a registry provides online resolver, CRS<url> When a registry is offline, CRSregistry: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

References

External links

Standards Catalogue entry for ISO 6709:2022 (Edition 3) Final draft of ISO 6709:2008 (archived) Profile by W3C GeoXG

Implementations Point Location 6709 - an open-source Java parser and formatter on GitHub Point Location 6709 - an open-source JavaScript implementation on GitHub C# Implementation Archived 2011-08-20 at the Wayback Machine at Codeplex Objective-C Implementation on GitHub

Illustrations

Worked examples

Example 1 — a first encounter with ISO 6709

Start with the simplest possible case. Write down what ISO 6709 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to ISO 6709 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about ISO 6709 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of ISO 6709

In research: ISO 6709 appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses ISO 6709 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: ISO 6709 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geographic coordinate systems, ISO/TC 211, ISO standards, so understanding it makes those chapters shorter.
In everyday life: Look for ISO 6709 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study ISO 6709 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what ISO 6709 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain ISO 6709 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is ISO 6709 in simple terms?

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 (ISO 6709:1983) was developed by ISO/IEC JTC 1/SC 32.

Why does ISO 6709 matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study ISO 6709?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on ISO 6709.