🚀 go-pugleaf

One of the current favorites is the Laser Gyroscope.
I believe these are being used in planes, boats, etc.

Kind of expensive, though.

I'd say, however, that your best bet would be to use
accelerometers in conjunction with a standard gyro.
When you get to a point in your motion that is most
stable while on the ground, you can then use the
accelerometers to tell where down is (gravity looks
like acceration), and use that information to recalibrate
your gyro.

You can also take into account the fact that vertical lines
exist alot in the world, especiall in man-made areas.  Use
a vision system with a simple vertical line detector.

petesk@microsoft.com
My Opinions...