Keyhole Markup Language

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Keyhole Markup Language
KML
File extension : .kml, .kmz
MIME type : application / vnd.google-earth.kml + xml, application / vnd.google-earth.kmz
Developed by: Google Inc.
Type: Markup language
Extended by: XML
Standard (s) : KML


Keyhole Markup Language ( KML ) is a markup language for describing spatial data . It became known through its use in the Google Earth program (which in its original version was called Keyhole Earth Viewer in allusion to a spy satellite project). KML followed the XML - syntax , available in version 2.2 before and is a standard of the Open Geospatial Consortium .

properties

Geometry elements

KML documents can contain spatial data in both vector and raster form . Vector objects such as points, lines, linear rings, polygons or COLLADA models are modeled as placemark elements and aerial and satellite images are modeled as GroundOverlay elements.

In addition to the geometry, placemark elements can include name, description, predefined style, viewing angle and height, a time stamp , but also any untyped or typed data, e.g. B. from a geographic information system . The same applies to a GroundOverlay element, whereby instead of the geometry, a coordinate section for georeferencing the raster data must be defined.

Example of a Placemark element within a KML document: 

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
<Document>
  <Placemark>
    <name>Zürich</name>
    <description>Zürich</description>
    <Point>
      <coordinates>8.55,47.3666667,0</coordinates>
    </Point>
  </Placemark>
</Document>
</kml>

Geodetic reference system

The World Geodetic System 1984 is used exclusively as the geodetic reference system in KML documents ; H. all coordinates are given with longitude and latitude and, if available, height above sea level . The height refers to the WGS84-EGM96 geoid.

MIME type

The KMZ format is a data-compressed KML file in the ZIP format . It can be read in by the client immediately.

The MIME type for KML files is application / vnd.google-earth.kml + xml or application / vnd.google-earth.kmz for KMZ files.

support

In addition to Google Earth, the free KDE program Marble also supports the KML format for route viewing, but only in OpenStreetMap mode.

history

The term "Keyhole" is derived from the product Keyhole EarthViewer from the California satellite imaging company Keyhole Corp. left over, which goes back to the name of a series of nearly 300 American spy satellites ( keyhole ). The company was taken over by Google Inc., also based in Mountain View , at the end of October 2004.

Google continued to develop KML up to version 2.2, which was recognized as a standard by the Open Geospatial Consortium in April 2008 and has been maintained since then.

See also

Web links

Individual evidence

  1. ↑ Open Geospatial Consortium: KML 2.2 - An OGC Best Practice ( english , PDF) Open Geospatial Consortium. 2007. Retrieved October 7, 2007.
  2. ↑ Open Geospatial Consortium: OGC® Approves KML as Open Standard ( english ) Open Geospatial Consortium. 2008. Retrieved October 8, 2007.