8.1 INTRODUCTION

Engineering surveying is concerned essentially with fixing the position of a point in two or three dimensions.

For example, in the production of a plan or map, one is concerned in the first instance with the accurate location of the relative position of survey points forming a framework, from which the position of topographic detail is fixed. Such a framework of points is referred to as a control network.

The same network used to locate topographic detail may also be used to set out points, defining the position, size and shape of the designed elements of the construction project.

Precise control networks are also used in the monitoring of deformation movements on all types of structures.

In all these situations the engineer is concerned with relative position, to varying degrees of accuracy and over areas of varying extent. In order to define position to the high accuracies required in engineering surveying, a suitable homogeneous coordinate system and reference datum must be adopted.

Depending on the accuracies required and the extent of the area of the project it may or may not be necessary to take the shape of the Earth into account. For small projects it may be possible to treat the reference surface of the project area as a plane, in which case the mathematics involved with finding coordinates of points from the observations associated with them relatively simple. If the shape of the reference surface needs to be taken into account then the process is rather...