We recently came across this interesting article on the DigitalGlobe blog. It is about using imagery crowd-sourcing site Tomnod to count seals in DigitalGlobe satellite imagery of Antarctica. The very best commercial satellite imagery available today has a resolution of about 30 cm per pixel, with most imagery that we call ‘high resolution’ satellite imagery closer to 50 cm per pixel. This usually means that animals are only a few pixels in an image and difficult or impossible to spot. In the cases where we have seen animals in Google Earth it has typically been in aerial imagery, such as the National Geographic Africa Megaflyover images or areas like the US which have a lot of aerial imagery. And there is, of course, Street View.
Antarctica has the advantage that we are looking for dark spots on a fairly featureless white background, which makes spotting seals possible. Much of Antarctica doesn’t have high resolution satellite imagery but there are some areas that have DigitalGlobe strips of imagery. So, given the tips in the DigitalGlobe blog post, we wondered whether we could find any seals in the imagery.
We aren’t certain if these dark spots are seals, but they do match the description given.
This is rather low resolution imagery but it does look like there might be groups of seals gathered around this crack in the ice.
We are fairly sure this is a positive find and that those are seals.
For the locations above, download this KML file.
Despite looking rather white and boring from a distance, it is well worth zooming in on Antarctica and looking around, as there is a remarkable variety of landscapes formed by glaciers and shifting sea ice. For best results switch to ‘historical imagery’ as it is much easier to find the high resolution patches that way.
We also tried looking for seals with the Tomnod website, but were unsuccessful. Google Earth is a much better interface for this sort of thing as it is much easier to find major features, such as cracks in the ice, then zoom in to them. The actual survey the scientists want, however, has to be done on Tomnod, because Google Earth does not have access to all the imagery that they want searched.