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Hurricane Followspot Animations

October 2nd, 2007 Leave a comment Go to comments

From top to bottom: hurricanes Florence, Gordon and Helene, 14th September 2006, in Google EarthGoogle Earth time animations of Atlantic hurricanes from 2006 – Ernesto, Florence, Gordon, Helene and Isaac.

One drawback of using animated sequences of picture overlays in Google Earth is that they tend to result in large, often memory hungry files.  With that in mind, I’ve been experimenting with some Python scripts that dynamically crop small regions out of large map images, then wrap them in KML.

This one is a quick mashup of hurricane tracking data from the National Oceanic & Atmospheric Administration (NOAA), and satellite imagery from the global cloud archive.  Rather than using a sequence of large rectangular(ish) overlays stuck over one area, every hurricane has its own set of circular image overlays, each centred on the eye of the storm.  When played back as a time animation in Google Earth  the satellite images move along with the weather feature.  The video shows it in action:

It comes in two versions:  opaque (GIF images) and one with transparency (PNG).  The GIF version contains higher detail imagery. Download either file here:

2006 Hurricanes (GIF) 7MB

2006 Hurricanes (PNG) 7MB

Note, you can change the transparency of either file using the slider in the Layers panel. It can take a while for everything to load into memory first time the file is opened.

A coupe of  noteworthy things about this:

  • For an animation using the full-sized global cloud PNG maps over the same time period,  the filesize would be 320MB! – that’s 40 day, 8 maps per day, 1MB each. 
  • Although not apparent in GE,  each image overlay is a slightly different shape to take into account spherical projection.