OT:ideas for oblique view tide-gauge ?

[N_Cook]

So not directly over tidal water , viewing horizontally the rise and
fall of tidal water over mud flats.
There is a change in light level , excluding fog, between veiwing the
mud and veiwing the water. Night time there is a lot of street-light
spill over , if moonless.
Perhaps a web-cam , with masked off view of a vertical slot with range
of angle from about -2 degrees to the horizontal , to about -50 deg,
with no boats, reed-beds or anything else in the view, just mud or
water. I assume it would be possible to digitally determine the
"terminator" as it moves up and down and initially generate a look-up
table comparing to a proper tide-gauge nearby, for the heights
corresponding to the image.
Any other ideas?

[Andy Burns]

N_Cook wrote:

> Any other ideas?

Rotate a polarising filter in front of the camera, look for differences
in the light reflected by water and mud?

[N_Cook]

Thats an interesting idea, but would that be sunlight only and rather
variable angle during the day?
I'm thinking of that early Viking navigation instrument of 2 slabs of
felspar on a viewing tube, to know the time, by rotating one wrt the other.