When looking around Google Earth in historical imagery, we have noticed an interesting trend with regards to the frequency of satellite imagery updates. It seems that Europe and the USA get significantly less satellite imagery than much of the rest of the world.
Although much of the less populated world has rather poor and infrequent coverage, some population centres seem to get very frequent updates. Here in Cape Town we have recently been getting several updates per month. We were recently looking at an area near Santos Dumont Airport, Rio de Janeiro, Brazil, and it has no less than 12 images so far in 2015. Even the relatively small town of Livingstone, Zambia has had two updates this year. Many large cities in the US and Europe, such as New York, San Francisco, Paris, Berlin and London still have 2014 imagery.
We have been wondering why this is. We will make a few guesses, but would welcome input from our readers too.
The USA and Europe are covered with high quality aerial imagery and thus new satellite imagery, which is of lower resolution, is usually relegated to ‘historical imagery’. Possibly Google, or the satellite imagery providers they source the imagery from, do not see the need for satellite imagery in those regions. Aerial imagery is typically more expensive to gather on a regular basis although we expect this to change in the future with as the cost of drones and high resolution cameras continues to fall.
Google tends to avoid satellite imagery with excessive cloud cover, and most notably, snow cover. So does this essentially mean that much of the Northern hemisphere will never get good coverage over the winter months?
Some of the recent Cape Town images can be explained as a ‘special event’ where imagery has been captured and put in Google Earth because it contains something interesting:
To see general trends up to October last year, this map is interesting. We hope Google updates it at some point to show more recent months.