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Kml and Its Applications


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Keyhole Markup Language (KML) is an XML notation for expressing geographic annotation and visualization within Internet-based, two-dimensional maps and three-dimensional Earth browsers.

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Kml and Its Applications

  2. 2. What is KML?  KML is type of markup language based off of XML.  Stands for Keyhole Markup Language  Developed by Keyhole Inc. Google  KML files are very often distributed in KMZ files, which are zipped KML files with a .kmz extension
  3. 3. Origin of KML  KML was first known as Keyhole.  KML originally developed for use with Google Earth.  Its development was engineered by Keyhole, Inc which Google acquired in 2004.
  4. 4. Definition  Keyhole Markup Language (KML) is an XML notation for expressing geographic annotation and visualization within Internet-based, two-dimensional maps and three- dimensional Earth browsers
  5. 5. In Other Words  KML is a way of displaying geographical data in an Earth Browser such as,
  6. 6. KML Functions KML includes features that allow it to display:  place marks  Images  Polygons  3D models  Textual descriptions
  7. 7. Example <?xml version="1.0" encoding="UTF-8"?> <kml xmlns=""> <Placemark> <description>New York City</description> <name>New York City</name> <Point> <coordinates>-74.006393,40.714172,0</coordinates> </Point> </Placemark> </kml>
  8. 8. This is the previous script:
  9. 9. KML Applications: KML file types are used by programs such as:  ArcGIS Explorer  Flickr  Google Earth  Google Maps  Google Mobile  Live Search Maps  Microsoft Virtual Earth  Marble (KDE)  World Wind  Yahoo Pipes
  10. 10. Google Maps and KML
  11. 11. KML Elements  Everything is an “Object”. (Everything inherits from the abstract “Object” KML element).  There are abstract elements  Everything is a tag: <Point>…</Point>  The more advanced tags are (usually) for Google Earth.
  12. 12. Google Maps supports a subset of KML… Google Maps supports…  Placemarks  Icons  Folders  Descriptive HTML  KMZ (compressed KML, including attached images)  Polylines and polygons  Styles for polylines and polygons, including color, fill, and opacity  Network links to import data dynamically  Ground overlays and screen overlays
  13. 13. Structure  KML is in XML format  Usually everything contained in Document tag  Can have multiple Folder tags to separate different kinds of data. For example, one folder containing KML to show locations of pictures and another folder containing KML to show your path through the day.
  14. 14. Placemarks/Points/Coordinates  The easiest element in KML.  A simple point on the map. It only needs a name and a location. You can give it a description too.  Placemark tag defines the place mark  A Point tag within it defines where the Placemark will be.  A “type” called coordinate defines the Point.  Coordinates in KML are given long,lat. When typing in coordinates directly into Google Maps, they are given lat,long. Be careful!
  15. 15. Contd.
  16. 16. Descriptive HTML  You’ll probably want to do HTML within the description tag.  You need to use the CDATA tag for this. If you don’t, your HTML’s tags need to use entity references:
  17. 17. Paths  Can define a path using the Placemark tag and the LineString tag instead of the Point tag.  Multiple coordinates. Again by long,lat,alt.  “extrude” tag makes the line go down to the ground  “tessellate” breaks each line into multiple pieces. Good for long lines so they don’t end up underground.  0 = false, 1 = true
  18. 18. Contd.
  19. 19. Advanced KML
  20. 20. Advanced KML  MIME Types  Styles  Screen Overlays  Network Links
  21. 21. MIME Type  KML Servers must follow certain rules  Must return response code of HTTP 200  The type itself is: application/  Can set the type in PHP with: header('Content-type: application/');  Body must contain valid KML data and the XML declaration: <?xml version="1.0" encoding="UTF-8"?>
  22. 22. Styles  Similar to CSS/HTML styles.  In a Style tag. Each style tag can have multiple styles within it: LineStyle, PolyStyle, ColorStyle, etc.  The tag has an “id” so it can be referenced within a file or from another. (A Global KML Style file perhaps?)  Add a styleUrl element to use a style.  HW2 could have different icons based on content? A site that grabs all the Google Map icons:
  23. 23. Contd.
  24. 24. Screen Overlays  Add an image to the Google Maps/Earth window.  Could be used for whatever purpose you like.  ScreenOverlay tag.  overlayXY and screenXY line up the image to the actual map  In this example, (0,1) (in fractions) means 0% of x (all the way to the left) and 100% of y (all the way to the top). The upper-left of the image is lined up with the upper-left of the map. The unit can also be determined by pixels.  Size tag (obviously) controls size of the image. 0 means to maintain aspect ratio, -1 indicate to use native dimension. Using some other value makes the image that value. For example 0.2 with units on fraction makes the image take up 20% of that dimension.
  25. 25. Contd.
  26. 26. Network Links  Allows importing of KML, KMZ, and image files for ground/screen overlays.  Local or remote file  Uses a Link tag  Good way to split up large KML file into much smaller KML files. More manageable.  More interesting feature: can use scripts to generate KML data on the fly. (PHP, Perl, etc.)  Usually uni-direction data flow (server to map) but when using “viewRefreshMode”, the map can pass the script information on what is being viewed (the LatLon box). Google Maps/Earth will call the script with a BBOX parameter. Look at the KML Tutorial for more information.
  27. 27. Contd.
  28. 28. Sources   rks
  29. 29. THANK YOU