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Bill wrote:

>> My question was, what are the negative numbers relative to?

Alex replied:
>
> Negative error means that it was an undershot.
> The measured altitude was less that the computed altitude.
>
> In general,
> error=measured value-true value.
> correction=true value-measured value=-error.
>
> Examples: dip correction in the almanac is always negative.
> Lower limb correction is always positive and upper limb correction always
> negative. Index error has the opposite sign of the Index correction.
> And so on.

First, apologies for an earlier post where I transposed the sources of the
"quotes."

Next, I envy your ability to keep things straight when dealing with signs
that are (to me) all but arbitrary in many cases. Words do seem to get in
the way.  Is "towards the body" plus and "away from the body" negative?
Perhaps anchored to how one first learned.

Starting in 229 with Susan P. Howell, the intercept was Hc - Ho.  She did
not pay much attention the the sign of the answer, and pretty much treated
it as an absolute value.  Then she applied an easy and simple to recall test
(for me).  HoMoTo.  Ho More Towards.  No mental gymnastic when rockin' and
rollin' on the water.  One simple test.

Perhaps not the best platform for intermediate or advances studies, but it
works on the water. 

Looking forward to your "sea trials" and photos,

Bill

   

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