Geoscience Reference
In-Depth Information
Chapter 2
Geodetic Data Collection Techniques
In order to accomplish the disciplinary tasks of geodesy, various geodetic data need
to be collected extensively. This chapter briefly introduces the methods and prin-
ciples of the data collection techniques that are commonly used in geodetic survey,
such as terrestrial triangulateration, height measurement, space geodetic surveying,
physical geodetic surveying, and so on.
2.1 Terrestrial Triangulateration
2.1.1 Angle Measurement
In establishing national geodetic control networks, it is often necessary to carry out
horizontal and vertical angle measurements. The theodolite is an instrument for
measuring angles with specific observational methods.
Horizontal and Vertical Angles
Horizontal Angle
In Fig.
2.1
, A, P
1
, and P
2
are three geodetic control points on the Earth's surface. Let
A be the point of observation and P
1
and P
2
be the target points. Through point A,
draw a plumb line AV (the direction of gravity) and a plane M, which is perpen-
dicular to AV. The plane M is called the horizontal plane through point A.
The line of intersection Aq
1
between the horizontal plane M and the vertical
plane containing the line of sight (line of collimation) formed by the plumb line AV
and the line of sight AP
1
is called the projection of AP
1
on the horizontal plane,
which is usually called the horizontal line (horizontal) of AP
1
. Similarly, Aq
2
is the
horizontal of AP
2
. The angle
β
between Aq
1
and Aq
2
is known as the horizontal
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