I would be extremely surprised if they were actually doing that, because a lot of effort has already been put into doing it a better (and more interesting) way:

I would be extremely surprised if they were actually doing that, because a lot of effort has already been put into doing it a better (and more interesting) way: cloud detection and mosaicing. Landsat captures several spectral bands, and due to atmospheric transmission rates, some bands can act as really good cloud filters [0]. This is what they're actually using, or something very close to it, for clouds [1]. [0] http://landsat.usgs.gov/ldcm_vs_previous.php http://landsat.usgs.gov/ldcm_vs_previous.php [1] https://github.com/USGS-EROS/espa-cloud-masking https://github.com/USGS-EROS/espa-cloud-masking