Surveying

Volume-I

Introduction:

• Surveying is defined as “taking a general view of, by observation and measurement determining the boundaries, size, position, quantity, condition, value etc. of land, estates, building, farms mines etc. and finally presenting the survey data in a suitable form”. This covers the work of the valuation surveyor, the quantity surveyor, the building surveyor, the mining surveyor and so forth, as well as the land surveyor.

• Another school of thought define surveying “as the act of making measurement of the relative position of natural and man made features on earth’s surface and the presentation of this information either graphically or numerically.

The process of surveying is therefore in three stages namely:

(i) Taking a general view:
This part of the definition is important as it indicates the need to obtain an overall picture of what is required before any type of survey work is undertaken. In land surveying, this is achieved during the reconnaissance study.

(ii) Observation and Measurement:
This part of the definition denotes the next stage of any survey, which in land surveying constitutes the measurement to determine the relative position and sizes of natural and artificial features on the land.

(iii) Presentation of Data:
The data collected in any survey must be presented in a form which allows the information to be clearly interpreted and understood by others. This presentation may take the form of written report, bills of quantities, datasheets, drawings and in land surveying maps and plan showing the features on the land.

Types of Surveying

On the basis of whether the curvature of the earth is taken into account or not,surveying can be divided into two main categories:

Plane surveying: is the type of surveying where the mean surface of the earth is considered as a plane. All angles are considered to be plane angles. For small areas less than 250 km2 plane surveying can safely be used. For most engineering projects such as canal, railway, highway, building, pipeline, etc constructions, this type of surveying is used. It is worth noting that the difference between an arc distance of 18.5 km and the subtended chord lying in the earth’s surface is 7 mm. Also the sum of the angles of a plane triangle and the sum of the angles in a spherical triangle differ by 1 second for a triangle on the earth’s surface having an area of 196 km2.

Geodetic surveying: is that branch of surveying, which takes into account the true shape
of the earth (spheroid).

Classification of surveying

Surveying is classified based on various criteria including the instruments used, purpose,
the area surveyed and the method used.

Classification on the Basis of Instruments Used.

i) Chain tape surveys
ii) Compass surveys
iii) Plane table surveys
iv) Theodolite surveys

Classification based on the surface and the area surveyed

1) Land survey

Land surveys are done for objects on the surface of the earth. It can be subdivided into:

(a) Topographic survey: This is for depicting the (hills, valleys, mountains, rivers, etc)
and man made features (roads, houses, settlements…) on the surface of the earth.

(b) Cadastral survey: is used to determining property boundaries including those of fields, houses, plots of land, etc.

(c) Engineering survey: is used to acquire the required data for the planning, design and
Execution of engineering projects like roads, bridges, canals, dams, railways, buildings,
etc.

(d) City surveys: The surveys involving the construction and development of towns including roads, drainage, water supply, sewage street network, etc, are generally referred to as city survey.

(2) Marine or Hydro graphic Survey: Those are surveys of large water bodies for navigation, tidal monitoring, the construction of harbors etc.

(3) Astronomical Survey:
Astronomical survey uses the observations of the heavenly bodies (sun, moon, stars etc)
to fix the absolute locations of places on the surface of the earth.

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