Google Earth has just had a makeover. Google has refreshed the global mosaic imagery that you see when zoomed out with newer, better quality imagery. When you zoom in, Google Earth transitions to higher resolution imagery where available, but in places where it is not available, the global mosaic remains. When Google Earth was first released it looked like a patchwork of imagery – essentially the same as it does today when you switch to ‘historical imagery’. Then, in 2012, they released ‘Pretty Earth’ a global mosaic derived from Landsat data which made Google Earth look a lot better. As far as we know, this is the first refresh to the global mosaic since then. The first mosaic was produced using Landsat 7 data. Landsat 7 has faulty instrumentation, which resulted in stripes in the imagery at some locations.
Read more about the new global mosaic on Google’s Lat Long Blog.
Landsat 8 was launched in 2013 and the new mosaic incorporates imagery it has gathered. However, we believe we can still detect, in places, the characteristic stripes of Landsat 7 data, suggesting that the mosaic is not exclusively from Landsat 8.
A location in Venezuela. The squares are roads. The broader, nearly horizontal stripes in the vegetation are almost certainly due to a Landsat 7 image being used.
Also see the Vatnajökull Glacier on Iceland for another location where the Landsat stripes are visible.
Overall, the contrast is higher in the new mosaic and in parts of the US you can see a distinct checkerboard pattern:
The checkerboard pattern is real, being a consequence of the Jefferson Grid.
The mosaic is created by carefully selecting cloud-free and snow-free sections of imagery from the catalogue of Landsat imagery. The resulting, largely cloud-free and snow-free view of the world is actually quite unrealistic. In some cases, such as some mountain ranges and the poles, it has proved impossible to find completely cloud-free, snow-free imagery.
Some clouds are visible in the Falklands.
The northern coast of Greenland hasn’t fared too well with the update, but that is because this is outside of Landsat’s coverage.
Overall, we think the new mosaic is a significant improvement, but without the old one to compare it with, it is difficult to make an accurate comparison.
As far as we know, Sentinel imagery is freely available under similar conditions to the Landsat data. In addition, it is higher resolution than Landsat data. We wonder whether Google has looked into incorporating Sentinel data in the global mosaic.
To find the locations mentioned in this post in Google Earth download this KML file.