Lots of work you have done there. Just wanted to let you know as someone who formerly worked in photogrammetric mapping and studied (to an extent) in this area, so by no means an expert, my observations is this: digital images must be “warped” to the shape of the earth and the focal distance must be corrected in correlation, the images must be overlayed to accomplish this- when working with aerial images. One cannot expect to lay a high resolution map on a lower resolution map and have it line up with any more precision the lowest res map has. Your interest in impervious surfaces has me laughing, coming from an area where they tax property owners extra for driveways and roof square footage, for rainwater runoff that goes into the sewer, supposedly causing expense–even though sewer treatment needs a source of water to process it… It is part of the new green deal ideology but stems from areas of the world where water is scarce and they fight over ownership of water rights. I can only think that your interest in driveways, roofs and little tunnel buildings and decks is related to planning a proposal for a new tax scheme. Funny you are on the other side of the Atlantic looking into the back yards of someone with such scrutiny. Do you own property at this site or are you doing land management for others?