NavList:

Actually, every now & then they use the cameras to do a sextant shot of the sun/demos/phobos to update their position. The rover’s on-board inclinometer serves as the AH.

Paul Dolkas

Hi Lu

You are absolutely right.  The original question was how to navigate on an extra-solar planet.

I think our first exemplar should be the Mars rovers.  They clearly don't use celestial or a GPS variant.  They navigate firstly by mark one eyeballs (binocular cameras if I'm not mistaken) and secondly by counting wheel revolutions and accounting for wheel slip.  So call it reckoning by track made good.  That's how vehicles navigate when not on the earth.  They look around, plan their course and check how they are doing visually.

In fact, for millennia, humans navigated across terra firma by eyeball, reference to landmarks (waypoints) and maps.  It was only the featureless environment of the oceans that required celestial.  Without oceans, no celestial would be required.  Make it easier? Yes!  Required? No!

Brad

: http://fer3.com/arc/m2.aspx?i=126992