Space exploration from a shirtsleeve environment

Henry Spencer wrote:
In article ,
Alan Anderson wrote:
That gives you attitude fixes, but it doesn't determine location on the
Moon unless you either have some closer reference (like Earth) as well,
or can measure the direction of the local vertical accurately.

Local vertical is easy: it's *down*.

It's easy only if your sensor is absolutely motionless during the
measurement period. This is not that easy to achieve aboard vehicles,
which are one of the major applications of such navigation devices.

Also, when you start wanting to get seriously accurate, you need a gravity
model of the Moon to determine the relationship between (so to speak)
local gravity vertical and local geometric vertical.

I think for lunar vehicles, a combination of inertial gyros, distance
measurement, and terrain contour mapping will be fine and cheap.

The Terrain Contour Mapping will be easy for a powerful enough computer
and some good optics.

An alternative is you shine a light to L1, and the L1 station tells you
where you are.