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Frank wrote:

> Bill you wrote:
> " I recall someone like own  FER mentioning something similar.  Of
> course I will not state that  someone like FER stated that or recommended
> that, as that might be construed  as an endorsement. "
>
> Indeed I have said that a little side error  can be a good thing. You have
> quoted me correctly! ;-)
>
> I think you're  joking here because I commented that I didn't recommend a
> pair of constants for  Bowdich Table 15 after you made a post listing "Frank's
> constants". I've been  thinking about writing all that up again since
> anomalous
> dip is a topic of  interest to list members again. My strong sense from the
> last run through was  that you didn't get my point, so I must have been
> unclear
> on this topic  previously (the discussion did sprawl over several months and
> one list outage).  I was not saying back then that there is a BETTER pair of
> constants than the  ones in the explanation to Bowditch --I was saying that
> the
> constants are not  constant. And furthermore that the variability in these
> parameters is generally  dependent on a quantity which the navigator cannot
> measure, namely, the lapse  rate in the lower layers of the atmosphere.

I do believe I understand/understood you.  Lapse rates, thermal inversions,
temperature and pressure, ducting and whatever make impossible to nail down
a "constant"  The "constants" are not constant. In essence, "Your mileage
will vary."

Let's replace "constant" with "starting point" or any other word(s) of your
choosing.  What I was doing was comparing lift from terrestrial refraction
between the Bowditch T15 starting point, the starting point you posted, and
the starting point used in the web site you pointed out, then experimenting
with those three starting points to see which got me closest under a variety
of conditions.  No initial value judgement on better or best.

Facts

Smallest lift:                   Bowditch
Considerably more lift:          0.15' per nautical mile
Largest, a bit more than 0.15':  Web site

Now before anyone calls the above "wooly" or "warm fuzzies," they are.  I
will be happy to send the MS Word file of my notes and calculations off list
if anyone is interested in specifics.

In LIMITED trials with the three starting points as well as application to
your beach shots, at the moment the starting point derived from the 0.15'
per nautical mile comes the closest to the GPS reading in my trials.

I have very few data points, so I encouraged others to run trials and report
them.  Perhaps my apparent systematic errors are skewing my results from an
undersized data pool.  I won't know until they are extensively tested.

Bill






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