NavList:

   

Reply

The standard deviation of his latitude is 3"=0.05'
(which can be expected with best sextants+art horizon
under good conditions). Comparison of the average lat
with the true value shows a small systematic error of
10" approx. 0.2' which can come from his almanach.

But the standard deviation of longitude is 0.3 deg,
that is 20' which probably better describes his accuracy
than the accidental fact that his average longitude is within
10' from the true value.

Now the standard deviation of longitude is expected to be
about 30 times standard deviation of the distance,
which gives us 0.7' for the standard deviation of
the distance, which from my point of view is not good.

(Since October 23, I measured lunar distances 10 times,
37 measurements in total,
the standard deviation is 0.3', (over the whole series of 37,
no preliminary averaging in groups), which I also think is not
very good,
and the average error (systematic component) was -0.3').

Is it his almanach that is responsible for this
scattering of measurements,
as Frank suggested? A 1800 almanac probably was not
very good in its Moon part.

But this is probably easy to check. If anyone has a 1800
(or around) almanach. Just compare it with Frank's online
lunar dist predictor. As I understand it gives accurate results
for the XIX century.

Alex.

On Thu, 9 Dec 2004, Ken Muldrew wrote:

> On 9 Dec 2004 at 16:09, Alexandre Eremenko wrote:
>
> > Thanks, Ken.
> > The "true position" was determined in modern times?
>
> Yes, the old forts are archealogical sites. There were 4 separate forts at
> Rocky Mountain House during the fur trade era; the one Thompson is at when
> he took the lunars that I gave was the first and it is very likely that
> this is the site of the true position that I gave (published with the
> archaelogical data) but there is also a possibility that Thompson's site
> was at a second site that is 1/2 mile closer to the mouth of the
> Clearwater River. Probably this "true position" was determined in the 60's
> or 70's.
>
> Ken Muldrew.
>

   

Reply