GPS for the moon

> If you wanted to set up a GPS for the moon, would it require the same
> number of satellites as for the Earth, or could you get away with less ?

> Was thinking GPS would be useful in Automation and Teleoperation operations.

Until recently the Sun and the stars were used in navigation on the Earth's oceans. From the surface of the Moon the positions of the stars can be measured much more accurately than through the Earth's atmosphere, and they are always visible. Of course the lunar horizon will rarely be flat enough to determine the plane perpendicular to local vertical with any great accuracy. Will mascons prevent the direction towards the lunar center from being accurately known by using gravity?
If you think of a positioning system which within a base area can determine an automated rover's or mining machine's location to within a meter, then navigation by the stars will not be nearly accurate enough. But with such localized operations you can have radio beacons placed around the base area.

Jon Lennart Beck.