storrence

It was just an estimate to explain the area closest to the water surface that I believe contains multiple refractions due to chaotic density variations . I think the effect doesn't get as high as 1.35m or at least is diminished. I'm not aware of another term describing it. I agree it's not very important to the test since it was describing the area obscuring the bottom of the boat and the laser should be higher than that.

Another way to describe it but the beam was above this supposed zone. This zone would be in the 50cm range above the water which is why the bottom of the boat seems to disappear. That is why we were looking for a term to describe what we thought was going on in that area which was a chaotic density zone that would cause chaotic refraction. NUDTZ was just easier to say than NUMRA

The laser was 1.25 above water level. That is above any supposed light bending due to refraction. With the conditions of the morning, refraction would have been up, not down. Air temp was cooler (denser) than water at the time of the measurements.

If you record and plot height against distance then it's not important if the laser is level or pointing slightly up since the data will mirror the shape of the surface when plotted. Are you suggesting this deviance is 1/2 km in 77km? Here is the elevation map of the area.

The laser was leveled using the boat so at 720 meters on the GE model, the beam should have risen from the surface from 1.25 starting height to 1.29. The ended up setting it to 1.32 because moving it in .01 adjustments proved difficult without an appropriate adjustable mount. What they were looking for was either a curve in the data plot against distance or an updward curve in the height data. What the test showed was a straight ascending line. The video shows the leveling at 9 minutes. https://youtu.be/GBhDFO4NMrw?t=9m

I can't show the calculation but from the way I understand it, refraction goes in the direction of higher density and with the measured lake temp higher than the air above, means it would have curved up since cooler air is denser. Sandor will probably post the calculation.

Refraction in this case would have curved the beam upwards. Michael, the 3.3ft on the right is correctly perpendicular to the surface. 14.3 looks like a straight line to me. Why do you think it's curved?