# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Measuring (and Calculating) Dip
Date: 2013 Mar 3, 13:31 -0800

Hi Greg

I wanted to separate the effects of a 'bobbing' vessel from the calculation of dip. The effects of the vessel will be related to the wavelength of the predominant waves and to the vessel's angle relative to the wave direction. Additionally, we would need to consider the bouyancy and the inertial mass of the vessel, as it reacts to the wave field. I think this a tremendous complication for right now and so I am measuring from a spit of land that is perhaps 100 feet wide and surrounded by water. For example, wind waves typically have a period of 4 to 6 seconds. I would think Jeremy's vessel would not be bobbing 12 times per minute, since the wavelength of the ocean wave is smaller than his vessel length AND he's hauling massive cargo. Compare that to my surfboard, carrying just me. A complication easily avoided by extracting ourselves to land. I think perhaps we could have a separate topic for this, if someone would start it off!

My estimation of wvhtCorr'n can be easily seen in the linked diagram. I have added waves to the diagram. If you observe by the lable Dip B, you will note the two purple tangent lines. One is to mean sea level, the other to wave crests. It is this small but appreciable angle that I am calculating and removing. (Note: all wave heights are grossly over sized, as is the height of eye. This is just done for illustrative purposes).

Regards

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