This application allows you to compare two maps easily and comprehensively, using the Google Earth browser plugin. An example use would be comparing two maps of the same place at different times; noteworthy comparisons can be saved as URL links. Movement of the Earths can be synchronized, and features such as buildings, roads and borders added.
Please refer to Google's documentation for guides to Google Earth and its navigation control.
Feel free contact me by email: contact(at)anotherearth(dot)org