LECTURE NOTES : WHAT IS SURVEYING?
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Surveying is the branch of applied mathematics which deals with measuring
and recording of the size and shape of any portion of the earth’s surface, and
the delineation of the same in a map or plan.
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It deals with the setting out of works such as roads, railways, waterworks,
drainage schemes etc and the calculation of areas and volumes.
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It may be taken to include levelling i.e. determination of the relative heights
of different points on the earth surface.
TYPES OF SURVEYING
1. Trigonometrical surveying : – This is for the preparation of maps of large
extents of territory
2. Land surveying: – this is ranging from the land division system and extensive
topographical surveys and work for boundary commission to small ones such
as farms and estates.
3. Hydrographical surveying: – ranging from coast surveys to plans for harbour works.
4. Engineering location surveying: – For the construction of highways, railways
and various public works.
5. Preliminary or parliamentary surveys: – This is in connection with a projected
scheme such as the construction of a railway or a waterworks.
6. Exploratory surveying: – This is for geological, engineering and mining
enterprises including archaeological expeditions.
7. Environmental survey: – his is survey carried out for forest and water
parameters.
DIFFERENCE BETWEEN SURVEYING AND LEVELLING:
Surveying consists in making measurements in the horizontal plane while
Levelling is making measurements in the vertical plane.
In surveying, the measurements consist in fixing position of points in the
horizontal plane; 2 points fix a straight line while 3 or more straight lines
determine the plan of a plane figure.
WHAT IS VISUAL SURVEY?
This is also called reconnaissance survey.
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It is the preliminary inspection of an area to be surveyed.
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It is a see-for-yourself walk-over of the ground to be used for a fish pond or a
fish farm. It is first done with a view to visualise the work to be done.
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It is the venture taken to note and identify all the parameters to be measured
or surveyed.
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It is a rough sketch of the field or fields in which all positions and stations
are made in the field book.
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It is preliminary work done whereby the routes of the main chain lines are
noted.
WHAT DO YOU DO DURING VISUAL SURVEY?
(i)
The purposes of the survey should be noted.
This includes (a) is it for pond construction?
(b) Is it for damming? (c) Is it for irrigation purposes; (d) Is it for Hydro-electric power (HEP)? The purpose will determine the extent of the reconnaissance survey.
(ii)
The water parameters to be measured should be noted as from the beginning. Such parameters include : (a) Water level; (b) Geological attributes;
(c) Soil conditions (texture, structure and permeability); (d) Water pH, hardness,
alkalinity, chloride, phosphate, ammonia, sulphide, sulphite, dissolved oxygen
etc
SURVEY IN POND CONSTRUCTION
Through topographic survey, the proposed site is inspected and professionally
approved. The water, soil and other parameters are determined. Using levelling
instrument, the topography of the site is ascertained and the area to be dug/
excavated or filled is pegged out with the use of lines.