Fire up Google Earth this morning and you’re in for a European treat. The base layers for Belgium, France, Spain and Portugal have been upgraded from the default global 15m/pixel Terrametrics TruEarth imagery to Spot Image‘s 2.5m/pixel imagery. Spot Image has a page with updated information about the process that generated the imagery:
One SPOT 5 image at 2.5-metre resolution covers 3600 km2.
We therefore needed over 500 images to cover Belgium, France, Luxembourg, Portugal and Spain.
The images were selected from among the most recent available in our catalogue, according to their quality and with as few clouds as possible.
First the images are put together like a giant patchwork and ortho-rectified so that the North is along the vertical axis and the distortion due to relief and viewing angle is removed, then the coverage is made seamless by defining the cut-lines so that the border between two images is virtually invisible (generally along a riverbank or the side of a building). We also take advantage of the overlap between images to get rid of the remaining clouds. The last step is to balance the contrast globally, so that the colours and contrast are as close as possible to the real landscape. [This text replaces an earlier draft.]
I may be wrong, but to the best of my recollection this is the first collaboration between Google and Spot Image.
I also noticed that several new high resolution DigitalGlobe tiles from 2006 are available in Belgium, where I tend to remember what wasn’t there; probably the same is true elsewhere on the globe [update: I was wrong, see comments], but alas I need to get back to work. Do let me know if you find anything.
[Update 1820 UTC: Here is the official press release from Spot Image and Google: I forgot all about Luxembourg!]