ir. W. Baarda who undertook the greater part of the contents, very cleverly
succeeded in making the results of his theoretical research subservient to
practice, this guide that developed into an extensive volume has indeed more
than cadastral significance.
By introducing the concept of relative accuracy of points, Prof. Baarda
comes to a reliable system of determination of points in an already existent
field of points, in which always the accuracy of the location of the given
points is taken into account.
Great attention is paid to the possible and desirable accuracy of the
measurement that ought to be tuned to the accuracy of the idealization of
physical quantities through lines and points and, as far as data are concerned
which Ought to be worked out graphically, into the accuracy of plotting. The
choice of certain methods and the technical execution of the different phases
are by this no longer voluntary but they always aim at reaching premised
relative accuracy, adjusted to the object and to local circumstances.
Great value is attached to the testing of measuring and calculation results
according to modern statistical methods which greatly enhances the scientific
value of this manual.
Theoretical development is only possible if a clear insight in the calculus
of observations can be obtained. An important contribution made to this
subject is the book on calculus of observations by the late Prof. Tienstra
compiled by his friends from his posthumous notes (i).
The methods of transformation are evolved by research of Prof. Baarda (2)
It is noticeable that all geodetic services and institutions make more use
of modern instruments. Not only the methods of indirect distance measuring,
(4) and (5), which among other things are applied by the Cadastral Service,
but also the possibilities of the electro-optical and electronic distance measuring
are studied. For some time the Hydrographic Office Royal Netherlands Navy
is using the geodimeter of Bergstrand.
In the period under review no new surveying instruments for general use
have been developed in the Netherlands. The development of methods and
auxiliary instruments for geodetic astronomy under the leadership of Prof.
R. Roelofs is worth mentioning. A new oscillographic instrument, the time-
signal oscillograph (T.S.O.) was designed; in it the time-signal as the chrono-
metertick are made visible on the screen of a cathode-raytube. Coincidence
takes place with the aid of an adjustable electronic delaying equipment (6).
The well-known sunprism has also been improved (7).
The application of modern aids in geodesy can also be established in
other fields, among other things by research concerning the introduction of
mechanical administration in the re-allotment procedure, the use of elec
tronic calculating machines and the application of tele-communication in
In the field of the surveying technique the results of Ir. P. Richardus who
applies the alignment-method by Van Heel for surveying purposes, are very
remarkable. In this method the pointing at an object is replaced by pointing
at an interference design that is shaped by placing certain diaphragms in
front of a pointed source of light. After laboratory research at Delft he
applied this method to distances till 50 km in the Australian Alps. He obtained
an accuracy nearly twice as great as in the case of normal direction meas
urement with the same instrument (8) and (9).
Among the most important activities of the Triangulation Service (Dienst
van de Rijksdriehoeksmeting) may be reckoned the primary measurements
in the province of Limburg. The purpose is replacement of the first-order
point Klifsberg which is threatened by the mining industry and the deter
mination of some first-order points along the Dutch-Belgian frontier.
However, in these measurements it has appeared that the central point Ubags-
bcrg is subjected to alterations which can only be explained by assuming
tectonic disturbances. Checking measurements are still going on in order to
know more about this phenomenon.