The entire work stages of survey operation in civil engineering may be divided into the following three stages:
- Field work
- Office work
- Care and adjustment of instruments
The field work consists of the measurement of all the necessary horizontal and vertical distances, horizontal and vertical angles, elevations, etc. and keeping a systematic record of what has been done in a field book. Field work is further subdivided into
(ii) field measurements or observations
(iii) field record.
During reconnaissance, the surveyor examines the area to be surveyed in order to know how the survey work can be performed in the best possible ways. He will fix a number of stations to establish a system of horizontal controls. He will also make a rough sketch of the area showing the stations and some permanent features including the north line. The sketch is not prepared according to scale, but it should represent the approximate positions of different features in the area so that it becomes a good guide for further work.
The surveyor takes all linear and angular measurement with survey instruments. The measurement includes horizontal and vertical distance, horizontal and vertical angles, etc. Method of measurement depends upon the nature of the terrain, type of instruments and the method of surveying.
All the measurements are recorded in a field book. The field records may be numerical values, sketches and explanatory notes. Every care is made to ensure correct entries of all the observations; otherwise the survey may be useless. The competency of a surveyor is judged by his field records.
The office work of a surveyor consists of three types based on the field records.
This process consists of preparation of plans, longitudinal sections and cross-sections by plotting the field measurements to the desired scale.
This process consists of calculating data necessary for plotting and determining the areas and volumes of earthwork.
This process consists of selecting the best alignment of roads, railways, canals, etc. on the plotted plan.
Care & Adjustment of Instruments
A great care is required to handle the survey instruments both in field and office. A beginner should always be made familiar with care and adjustment of the instruments and their limitations. Precise instruments like theodolite, level, prismatic compass, etc. need more care than the equipment such as chains, arrows, ranging rods, etc.