Just spent some time down at the Antarctic festival. There was a neat display of the way they track the seabirds with miniture tags that record
ambient light and temperature against time over a few years.
The results are post processed when the tags are recovered from the nesting areas to give a length of day type calc, using two methods, old school
length of day, and using the shape of the curves for morning and evening.
This infomation is combined with the temperature data and DR calcs to give about 60NM resolution from a device about the size of my fingernail. Pretty impressive.
I cant help comparing it to this case of emergency navigation