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 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.
A geographical point is specified by the following four items:
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, 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:
There is no such interpretation rule for vertical coordinates.
When there is no guideline given from the user community, the following styles are suggested:
The XML representation based on the conceptual model of Annex C uses XML namespace [www.isotc211.org][permanent dead link]. However, there is no published XML schema at the time of writing (August 2011).
<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>
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 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.
|6||deg, min, sec||±DDMMSS.S||+401213.1|
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.
|7||deg, min, sec||±DDDMMSS.S||-0750015.1|
The CRS identifier begins with "CRS". There are three styles:
The example of original Annex H always use "CRSWGS_84".
Sas sign characters, but gives no examples.
Was sign characters, but gives no examples.