Google intentially reduce the definition of some of the higher resolution areas on the free google earth system. I know this because recently I was inspecting a presentaltion for a local possible planning application for land at the back of my house. I recognised the aerial photograph - the colour and position of the parked cars, the lack of certain recently added extensions and conservatories and in the bottom rhight hand corner was the copyright Google symbol. However this paid for photograph was of much higher definition than the indentical image I was used to on my computer screen.
P.P.