Hurricane Followspot Animations
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:
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.