20
V
*2.
' = -dy,,+ —dy TT + % dc- ds-x'd^c + ---^-da? -(l+ •"—-) edeo - — dt- -dl-
•tr 2 C ^ n ~ K 9 ' « a
., .45° 2 de ç /^4^.° 2 ae „ _
c 10
z
aSl1 _ 'ÆÎ'o'^ 21 ' « vx- + e-
( 18 )
(g-yQ fx' 2 +y' 2 +c‘
S \/x' 2 +c 2
de i2 - (-^
x
\/x' 2 +c 2
limité) de , zlag.3,. de
se ' 22 /—-—^-32 7
s vx" +c
The following notations are used in (is):
^ e l0 = c ° rrec ^i° n to the eccentricity between the projection ray and
the tertiary axis in the y-direction in the projection centre .
de^ = the correction to the eccentricity between the projection ray and
the tertiary axis in the x-direction in the projection centre .
de^Q = the correction to the eccentricity between the primary and secondary
axis in the projection centre.
den = the
correction corresponding
to
de io
below
the projection centre.
fle l2 =
_ tt _
above
_ tt _
de 21 =
_ it _
to
de 20
belo?/
_ tt _
de 22 =
_ tt _
above
_ tt _
de 31 =
_ tt _
to
de 30
below
_ tt _
de 32 =
_ tt _
above
_ tt _
Hot all of these eccentricities are adjustable. Thus they can be regarded
as errors due partly to manufacturing methods. They should not normally,
however, be significant. The solution with these 20 elements ha.s not been
performed but it is possible. If the standard error of unit weight from 11
elements is veiy large it is possible that it may be the result of these
errors. It is known from practical experience that de^ Q can sometimes appear
in AT autographs^ but, normally, significant eccentricity errors in autographs
occur only in exceptional cases. Thus, normally 11 elements can be considered
to be enough. Ho thorough investigations have, however, been performed in
connection with this problem.