NavList:

John,

I mistakenly assumed that the online distance by vertical angle beyond the horizon calculator applied dip.

http://msi.nga.mil/NGAPortal/MSI.portal?_nfpb=true&_pageLabel=msi_portal_page_145&calcCode=03

A quick compare to Bowditch table 9 shows that it doesn't. The Anacapa Island Peak image distance by vertical angle now more closely matches the charted distance and towers only by 1' moa not 5' moa.

Greg Rudzinski

[NavList] Re: Dip Short Puzzle
From: gregrudzinski---com
Date: 5 Dec 2011 13:24

John,

Yesterday had the air temp at 65 F with the water temp at 53 F. Santa Ana winds can blow in with temps over 80 F at very low humidity. What I noticed after working up distances short and beyond the horizon is that the horizon from a 19 ft. height of eye is low by 1 moa and Anacapa Island peaks are high by 5 moa. This gives the islands a towering look.

It was discovered that the breakwall lights are 10 ft taller than the chart listing (old chart). This threw me for a loop. The jetty lights worked out as expected with the charted heights.

When using the online lapse rate and dip calculator be sure to convert to nautical miles. For some reason the results are in statute miles and kilometers which messes things up for us navigators.

Greg Rudzinski

P.S. Anacapa Peak is measured at 383 px (37.4' moa)

[NavList] Re: Dip Short Puzzle
From: apacherunner---com
Date: 5 Dec 2011 14:02

Greg -

I haven't had time to work it out, but, gad!! that's an amazing photo. So, the conditions are what over the water? I have been reading in the news about the freak Santa Anna winds, and as I recall they're quite hot, so you have very hot air over cold water, which will create some interesting conditions.

Is there a rough air temp and a rough water temp you know of?

John H.

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