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Bill,

I noticed differences in intercepts when using the Nautical Almanac tables vs NC-77 Tamaya and Palm Pilot (ver. 6.9). The NC-77 uses the Radau model. Not sure what the Palm Pilot uses. USNO doesn't provide 0° refraction data :(  Hard to say what qualifies as good on these sunset horizon sights. 

Greg Rudzinski 

From: Bill B
Date: 2015 Apr 07, 16:47 -0400

 

On 3/28/2015 9:06 PM, Greg Rudzinski wrote:
> You may want to try using Neptune's Net position as an assumed position
> to generate an azimuth and intercept. The intercept should be less than
> a mile.

Taxes filed, so it was time to quit having fun and get back to toiling
away on your suggestion :-)

Plotting in Google Earth turned out to be a hassle. When I added a
placemark its displayed lat and lon drifted depending on zoom level.
Adding lines is also a bit bizarre. It does seems to deal OK in nautical
miles or feet, but does not adjust lateral lines for latitude if using
the degrees or arc seconds option. In long range testing it does
generate the great circle route, and properly reports a line bearing at
or close to the initial great-circle course. To avoid attaching too many
images, I'll follow up on that in a subsequent post.

The long and short time-sight COP/LOPs were generated assuming a 50'
height of eye. Bill's Final location is a position (this time on the
coast) where a 50' height-of-eye Ho matches the USNO Hc.

Intercepts were 1!2 and 1!9 depending on height of eye. As the azimuth
of 273.1d was close to lateral, I plotted by multiplying feet or
nautical miles by the cosine of 34d 03'.