Introduction - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 1

Chapter 1
Introduction
Geodesy is a subdiscipline of geomatics and surveying and mapping as well as
geoscience. It plays a pivotal role in construction of the national economy geosci-
ence research, and in the process of social informatization. Advancement of modern
science and technology has allowed geodesy to undergo an epoch-making trans-
formation, to break the temporal and spatial limitations of traditional classical
geodesy, and to enter a new stage of development of modern geodesy, primarily
of space geodesy.
This chapter briefly introduces the disciplinary objectives, applications, history,
and trends in the development of geodesy.
1.1 Objectives and Classifications of Geodesy
1.1.1 Objectives of Geodesy
According to the classical definition given by F.R. Helmert in 1880, geodesy is the
“science of the measurement and mapping of the Earth's surface.” This definition
has to this day retained its validity; it includes the determination of the Earth's
external gravity field as well as the surface of the ocean floor. With this definition,
which has to be extended to include temporal variations of the Earth and its gravity
field, geodesy may be included in the geosciences and also in the engineering
sciences (Torge and M¨ ller 2012; Helmert 1880).
The objectives of geodesy, generated from and partially supplementing
Helmert's definition, can be described comprehensively as, first, to determine
accurately the positions of points on the Earth's surface and their variations and,
second, to study the gravity field of the Earth, the shape and size of the Earth, and
the geodynamic phenomena. The former is generally considered the practical
objective of geodesy and the latter the scientific objective. These two objectives
are closely correlated.