I wish Google Earth would date their images. I know at my home it has been several years since they re-imaged, I can see my pickup in the yard with my car trailer attached and a blue tarp over some building supplies, I therefore know when it was.
My remote property, I have no idea and it is also much lower resolution images.quote]
You might locate an aerial survey outfit nearby and ask them when their last images were ...I did and got a hi-res scanned image and bought several hard copies ...More interestingly, they offered to "fly a mission" for me and the price was surprisingly low (of course, they might resell the imagery many times, but so what...)
Incidentally, I don't mean to start an argument, but 5mm ...millimeters? More like 3-5 centimeters is best one can do ...has to do with how accurately the position of the satellites is known (and that is not constant) and their position is gauged from some well-surveyed ground station's! ...whose antenna feed points are known to about 3cm vis a vis the "center of the earth".
Perhaps you should read this. It may be possible.
Differential GPS
Up to this point, all of the GPS calculations discussed have been concerned with locating a single point in space, but one of the best ways to increase the accuracy of the GPS calculations is to perform GPS observations on two points at the same time, a technique known as differential GPS.
When using differential GPS (DGPS), one receiver is used as a reference station. This receiver is set up over a point with known coordinates. Another receiver is used to determine the location of the unknown point. While the GPS data is being collected at the two points simultaneously, the distance between the two receivers remains constant. Introducing the constant baseline between the two receivers into the GPS calculation increases the positional accuracy significantly. When using the C/A code only, DGPS can achieve accuracy in the range of 30 centimeters. With more sophisticated receivers that use code and carrier to calculate positions can achieve accuracies approaching 5 millimeters.