Aeronautics -- Flights; Arctic regions; North Pole
Taking an observation of the sun’s altitude, with a simultaneous noting
of the clock’s striking, can be done most rationally by describing a
tangent from a local circle in the neighborhood of the place where
one believes oneself to be. Such a tangent should be called a local
line. In the neighborhood of the Pole it is easy to find local lines
without scientific calculations. The meridian the sun is in can be
found directly one has calculated the clock’s stroke by G.T.T. The
local circle cuts the meridian in the distance h--d from the Pole,
where d signifies the sun’s declination. This cutting-point we will
call the local circle’s Pole point. If the difference h--d is positive,
this point will be on the same side of the Pole as the sun, should
it be negative it will be on the opposite side. A line dropped on
the meridian which the sun is in, through the local circle’s Pole
point, describes a tangent from the local circle. We will call this
tangent the “Pole tangent.” At a distance from the Pole point equal
to 5° of latitude, the Pole point will represent the local circle
with sufficient exactitude, and can be considered as a local line.
But if the distance increases, the tangent’s divergence from the
circle will be noticeable. Sverdrup explains how, by an easy method,
one can calculate the corrections which have to be made, should one
find oneself within the above-mentioned limits from the Pole. During
our observations in the ice region we were always within the limit,
and had therefore no need for corrections. The method is of course
particularly simple and sufficiently exact because there is so little
difference between the hour-angle and azimuth. I here give a table of
our observations on the night of the 22nd immediately after landing:
Clock readings: 3 h 23′ 3″
Error -1 h 0′ 19″
------------------------------
G.M.T. 2 h 22′ 44″
Time level + 3′ 33″
------------------------------
G.T.T. 2 h 25′ 17″
Converted into
degrees: 36° 3′
Sun’s lower
rim from the
imaginary
horizon measured 35° 58′ 2″
Half of this 17° 59′
Mistakes: 0
Corrections + 13′
-----------
Sun’s center
correct altitude 18° 12′
Sun’s declination 20° 15′ 4″
-----------
h--d: - 2° 3′ 4″
Converted into
nautical miles 123.4
On a chart we drew a line representing Greenwich meridian, and a point
on that was selected as the North Pole. The angle 36° 3′ was set from
north to east and the sun’s meridian drawn through the North Pole. From
the last named point towards the southwest we marked out 123.4 nautical
miles, as the h--d was negative we drew the local line straight up to
the sun’s meridian.
Public-domain text, read in full here on John Shaqi.
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