GovHack 2014: Landsat Timelapse

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Australia has a vast archive of satellite imagery stretching back many years. This data has been processed to correct for variations in weather and sunlight and represents a unique opportunity to reach back and see how this country has changed over time. Landsat Time Lapse Journey seeks to enable easy viewing of historical Landsat data all across Australia. Simply enter an Australian postcode, and hit Go to find imagery data for your location. A timeline appears at the bottom of the application, showing where you are in time. As the day a Landsat image was captured approaches, the image fades in, becoming fully opaque for that day before fading out again. While it vanishes, the next image fades in, producing a blending effect.

Once you’re done hit Go Again! to continue exploring.

View the app online here: Landsat Timelapse Journey

Technology

  • Cesium JS
  • Node.js
  • HTML5
  • jQuery and JavaScript
  • XML
  • Web Services

API Reference

Australian Reflectance Grid 25 (ARG25) ARG25 data is accessed in a two-stage process. First, the catalogue service is queried using the base URL http://eos.ga.gov.au/geonetwork/srv/en/csw?service=CSW, with the desired bounding box sent as POST data. The catalogue responds with a list of URL endpoints that can be queried to retrieve image data.

These URLs have base form http://eos.ga.gov.au/thredds/wms/LANDSAT/2008/10/LS7_ETM_NBAR_P54_GANBAR01-002_115_079_20081021_BX.nc, to which is appended the colour layer desired and bounding box coordinates. The result of this request is an image of the specified location at a particular point in time. In this example, the LS7_ETM_NBAR_P54_GANBAR01-002_115_079_20081021_BX part is retrieved from the catalogue request, and specifies a particular satellite and global region.

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