Is Keyhole Markup Language (KML) becoming the defacto Spatial Transfer Protocol?

With the widespread adoption of Google Earth (GE) – the ‘free’ 3D web visualiser with intuitive navigation – its scripting language, KML, has become an effective means for users to create and share information. This early adoption of KML likely undermines the purpose of the OGC’s complex Geographic Markup Language (GML) protocols being slowly developed by internationally bodies – yet I believe KML is also stimulating a sluggish giant (the geocommunity) into action. The acceptance of KML by the (geo)community has not been missed, over the past year the basic KML specifications have evolved and a plethora of GIS individuals and vendors have provided tools to aid the geo-community to publish via KML.

Google Earth’s KML originated as the XML script for users of its predecessor (Keyhole – a Commercialised CIA Project) to add locations onto their maps and assign bookmarks to the applications display. Today’s KML specifications not only provide display and navigation parameters but also support data and processes previously limited to sophisticated GISystems – lines, polygons, images and textured 3D objects with their attributes and hyperlinks; streaming of very large datasets from remote websites, with “smart” loading of data at multiple levels of resolution; incremental updates with data loaded by NetworkLinks; display of table of content folders; …..

The GIS community has been quick to provide export tools to KML so they could use the ‘free’ GE as a publication media. For example, ESRI ArcGIS Extensions (Arc2Earth , KMLer, Shape2Earth, …) provide professional commercial products to convert layers, data frames, graphics and whole ArcGIS mxd project files into KML and vice-versa; NASA World Wind (‘the free GE for research geeks’) has extensions to do similar; and ESRI currently has its own Google Earth equivalent (ArcGIS Explorer – AGX) in late beta – AGX is officially scheduled for release along with ArcGIS 9.2 in Qtr4 2006 (though I expect a sooner release). Importantly, both the ArcGIS 9.2 and ArcGIS Explorer (AGX) specs say they will read/write KML directly, finally ending Google Earth’s (and recently, its sister Google Maps’) exclusive direct readability of KML and addressing the recent tightening of GE user licensing.

Google Earth’s End User License Agreement (EULA) has recently explicitly excluded the loading of the free GE and inexpensive GE Plus applications on business owned computers. Requiring businesses to purchase the $400/seat Pro or Enterprise GE versions. Note that Google Maps’ EULA appears to still offer its mapping service to businesses for free. If others can interpret the technical legalise of the Google Maps EULA and confirm whether business users can publish KML to GM for their end users (and their ‘business audience’ to freely view the KML in GM) please let us know.

So, will ArcGIS Explorer (AGX) be free? The recent news about its public beta say so, and I suspect it will remain free given ESRI backend applications – which supply much of the data and resources for these popular publishing platforms – will likely be in high demand while it is free to use. The geo-community quickly accepts free software that answers issues such as ‘how can I quickly (and cost effectively) show my maps to the world?’ Let’s just hope ESRI does not do the Google on us.

Has OGC and the International Standards Organisation (ISO) lost its opportunity to implement its well designed GML protocol? Time will tell.

Ciao from Tomt


3 Responses to “Is Keyhole Markup Language (KML) becoming the defacto Spatial Transfer Protocol?”

  1. Carl Reed Says:


    Just happened to find your blog. There is a fundamental confusion in the geo-community mindset regarding the problem domains that KML and GML solve. Yes, there is some overlap in functionality. However, these are not competing standards – and yes, I would suggest that KML has become a de-facto standard.

    The OGC membership discussed the market perception of KML and GML at our face to face meetings last week. There is agreement that we need a document (white paper) that describes the respective roles of GML and KML. Stay tuned for some interesting announcements in this regard!


  2. Tomt Says:


    Thankyou for your interest in my (dated) blog. It was (then) meant to open the eyes of fellow spatial scientists to the likely impacts from Google’s drive into our sphere. I am looking forward to learn how OGC’s ‘Mass Market’ working group is going to join-the-dots between the established spatial information community and the rapidly developing mass geospatial market. ISO I fear is a goliath who may be left behind.

    With NASA’s drive using GEarth as a viewer in coming months, I think it imperative that some cohesive industry stds exist to build our future interoperabilty/integratability initiatives. I turn to OGC for that foundation.


  3. hadid Says:

    i need kml for gis

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