INTRODUCTION This chapter describes the various heighting procedures used to obtain the elevation of points of interest above or below a reference datum. The most commonly used reference datum is mean sea level (MSL). There is no such thing as a common global MSL, as it varies from place to place depending on local conditions….
The basic concept of errors in the data captured by the surveyor may be likened to target shooting. In the first instance, let us assume that a skilled marksman used a rifle with a bent sight, which resulted in his shooting producing a scatter of shots as at A in Figure 2.1. That the marksman…
It should now be apparent that position fixing simply involves the measurement of angles and distance. However, all measurements, no matter how carefully executed, will contain error, and so the true value of a measurement is never known. It follows from this that if the true value is never known, the true error can never…
The system most commonly used for the definition of units of measurement, for example of distance and angle, is the ‘Système Internationale’, abbreviated to SI. The basic units of prime interest are: Length in metres (m) from which we have: Significant Figures Engineers and surveyors communicate a great deal of their professional information using numbers. It…
In surveying nothing is ever absolutely certain. The product of surveying may be thought of as being in two parts, that is, the derivation of the desired quantities such as coordinates of, or distances between, points, and the assessment and management of the uncertainty of those quantities. In other words not only must the survey…
In the past, detail would have been plotted on paper or a more stable medium such as plastic film. However, today all practical ‘plotting ‘is computer based and there is now an abundance of computer plotting software available that will not only produce a contour plot but also supply three-dimensional views, digital ground models, earthwork…
Establishing control networks and their subsequent computation leads to an implied rectangular coordinate system over the area surveyed. The minor control points in particular can now be used to position topographic data and control the setting out of a construction design. The methods of topographic survey and dimensional control will most probably be: (a) by…
The establishment of two- or three-dimensional control networks is the most fundamental operation in the surveying of large or small areas of land. Control networks comprise a series of points or positions which are spatially located for the purpose of topographic surveying, for the control of supplementary points, or dimensional control on site. The process…
· It is a surveying method used to determine the level of points/objects with reference to the selected datum. · It is also used to set out engineering works. Uses of Levelling: · To determine the difference in levels of points/Objects · To obtain contour map of an area · To obtain cross section of roads, canals etc., · To determine…
Solution : Line PA lies in 1st quadrant. Quadrant Bearing of PA = N 35o 15’ E Solution : Line PB lies in 2nd quadrant. Quadrant Bearing bearing of PB = S 50o 00’ E Solution : Line PC lies in 3rd quadrant. Quadrant Bearing bearing of PC = S 30o 15’ W Solution : Line PD lies in…