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162 DE TWEEDE NAUWKEURlGHElDSWATERPASSING VAN NEDERLAND
weighting coefficients Qp Refer to table 13; in this table the values of 100 Qv are given, not Qv
itself.
The 67 corrections E, derived from the correlates K, are shown in table 9. Finally the levels of
the nodal points and important intermediate points relative to N.A.P. were calculated using
the corrected rises and falls, starting with R.B. Ouder Amstel3 in loops 7 and 10 (par. 4.3). In
this connection, refer to the schedule of observations and results (table 32) in Chapter 11.
As a final check
and the estimate for the variancefactor
were calculated.
9.3 Calculating the remainder of the network
The lines not included in the main network were fed into it. In the provinces North and South
Holland artd in the North of Friesland a number of loops were adjusted together; otherwise it
was a matter of calculating a number of combined or single lines. Refer to table 32 in Chap-
ter 11.
Finally the levels of the individual benchmarks in all the lines were calculated using the
summary sheets (par. 6.5.2), starting from the adjusted levels of the nodal points.
These definitive levels were entered in the records with the column "connected to" showing
"Amsterdam, N.A.P. 1940".
Chapter .l0 ACCURACY OF LEVELLING AND RESULTS
10.1 Standard deviation of the readings
The following can be derived from the differences in the back and forth levelling in the 1739
sections:
im=
U, = 'h 0.66 mm.
The values of U, in the various years are shown in table 14. The total number of measurements
that did not come within the tolerance, expressed as a percentage, is also shown. A high
percentage indicates that during the period 1926-1930 the tolerance was too small in relation
to the accuracy of measurement, so that the calculated value for U, in this period presents a
too favourable picture.
Various data about the second geodetic levelling were assembled for the I.A.G. General
Assembly at Oslo in 1948.
These data provide yet another way of calculating the standard deviation per kilometre.