about googleMap and googleEarth

The image from googleMap or google earth is very clear, and sometimes you can see you roof of your build, even your car.

From this point, the precision of google map should be very high. But the truth should be different.

The root cause is something related to how those images are created, generally they are taken by aviation remote sensing through a moving airplane or a satellite.

The earth itself is not plane, and the image quality also is affected by how camera is set. Actually everything in the remote sensing image is contorted. Although it looks very clear, the actual position however is not right.

Suppose you are driving in car, you can clearly catch everything in the mirror of your car, and you definitely know everything is contored in your convex mirror. Similarily, google map is just like that.

Of course, the data provider should do some data collection for the raw image, however the resule should be very course. If you want to get a very clear and very precise image, you should correct everything in very small area.

It is just personal view, you know, I have no enough time to do such check.

Anyway, it is funny that you can find your root throught those picture.