I use oziexplorer and have just today finished creating and calibrating a huge number of detailed goldfield maps whilst locked in with covid restrictions.
Ive been using the online state geological maps (australia based) which have a lot of data such as old mines, geology ,topography etc. but have used google earth overlays too and that worked well.
found it fastest to take a screenshot of GE image or map and , edit the map in ms paint, then calibrate it with Oziexplorer.
Its pretty accurate ,but there may be better stuff out there. works well on my android phone n tablet