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Kml and Its Applications
KML, or Keyhole Markup Language, is an XML-based language developed by Keyhole, Inc. for geographic visualization in applications like Google Earth and Google Maps. It allows users to create and display elements such as placemarks, images, polygons, and paths in two-dimensional and three-dimensional map environments. KML files can be distributed in KMZ format and support advanced features like style definitions, screen overlays, and network links for dynamic data import.
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Kml and Its Applications
- 1. KML ASHOK BASNET (066BCT505) BIKRAMTHAPA (066BCT508) SUPRITAM RAJ SHRESTHA (066BCT542)
- 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. 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. Definition Keyhole MarkupLanguage (KML) is an XML notation for expressing geographic annotation and visualization within Internet-based, two-dimensional maps and three- dimensional Earth browsers
- 5. In Other Words KML is a way of displaying geographical data in an Earth Browser such as,
- 6. KML Functions KML includesfeatures that allow it to display: place marks Images Polygons 3D models Textual descriptions
- 7. Example <?xml version="1.0" encoding="UTF-8"?> <kmlxmlns="http://earth.google.com/kml/2.0"> <Placemark> <description>New York City</description> <name>New York City</name> <Point> <coordinates>-74.006393,40.714172,0</coordinates> </Point> </Placemark> </kml>
- 8. This is theprevious script:
- 9. KML Applications: KML filetypes 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
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- 11. KML Elements Everythingis 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. Google Maps supportsa 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. Structure KML isin 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. Placemarks/Points/Coordinates The easiestelement 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!
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- 16. Descriptive HTML You’llprobably 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. Paths Can definea 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
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- 20. Advanced KML MIMETypes Styles Screen Overlays Network Links
- 21. MIME Type KMLServers must follow certain rules Must return response code of HTTP 200 The type itself is: application/vnd.google-earth.kml+xml Can set the type in PHP with: header('Content-type: application/vnd.google-earth.kml+xml'); Body must contain valid KML data and the XML declaration: <?xml version="1.0" encoding="UTF-8"?>
- 22. Styles Similar toCSS/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: http://www.visual-case.it/cgi-bin/vc/GMapsIcons.pl
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- 24. Screen Overlays Addan 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.
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- 26. Network Links Allowsimporting 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.
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