Stages of Survey Operations

Survey operations involves the following:
1. Planning the survey work.
2. Selecting appropriate instruments depending upon the nature of survey.
3. Organizing field survey operations.
4. Collecting and recording data from the field by taking linear and angular measurements.
5. Office work like calculations and plotting.
6. Taking care of instruments through periodic maintenance.
However, the entire survey operation may be divided into three distinct stages:
1. Field work
2. Office work
3. Care and adjustments of the instruments.

1.Field Work

Fieldwork in surveying involves selecting instruments for a particular job, taking linear and angular measurements in the field, and recording data in proper forms along with field notes and sketches. Field work is further divided into three stages:
a) Reconnaissance
(b) Field observationsl
(e) Field record.

(a) Reconnaissance:

While conducting reconnaissance, the surveyor goes over the area to select and fix a number of stations, ensuring necessary intervisibility, to establish a system of horizontal control. A few permanent stations are also selected for an extension of the survey in future.

(b) Field Observations:

The surveyor makes necessary field observations with appropriate instruments for linear and angular measurements. It include determination of differences in elevations between the stations, also establishing points of given elevations. The method of observation depends upon the nature of the terrain, type of the instruments used and the method of surveying.
The following operations should be done by field surveyor during field work:
• Selection of sites and establishment of stations and bench marks in the area.
• Measuring the horizontal distances between stations either by chaining on the surface of the earth or by trigonometrical computation.
• Locating the details with respect to survey lines either by chain surveying or by plane tabling.
•Establishing of elevations of stations and bench marks either by levelling or by trigonometrical levelling.
• Surveying contour of land areas or Digital Elevation Modelling (DEM).
• Determination of longitude, latitude or local time by making astronomical observations to either sun or stars (or) by taking GPS co-ordinates.

(c) Field Record:

Field records are a very important part of the fieldwork. These are the only source of survey data available after the field work is over. Different formats are used for recording field data obtained using different types of Instruments used and different methods of survey. Enough notes and sketches should be made for relating any future work to the surveyed field stations. The competency of a surveyor is judged by his field record.
The following points to be kept in mind while recording field observations:
•Only one field book should be maintained.
• Entries should be made by a sharp 2H pencil, this keeps the field book neat and clean.
• Never erase wrong readings. Rule one line through the incorrect value and record the correct reading above it.
• After completion of each days work, the field notes must be signed

2 Office Work:

After completion of field work, the field record is brought to office and necessary calculations, drafting and designing is done for different purposes. The office work involves the following:
• Analysing the data, making various calculations to check the data and correct the data as per standard practice.
•Prepare plans and maps to standard scale using the collected data.
•Determines the areas and volumes for earth work.
•Locating various engineering structures, and projects in the plans and maps, drawing contours, locating gradient lines, etch.
•Selection of best alignments of roads, railways, canals etc.. on the plotted plans.

3 .Care and Adjustments of the Instruments:

A great care is required to handle survey instruments. A beginner should always be made familiar with care and adjustment of the instruments and its limitations. Precise instruments such as compass, level, theodolite, EDM, other electronic survey instruments need more care than the equipment such as chains, arrows, ranging rods etc. The following points should be noted while using these instruments.
• The manufacturer’s instructions must be carefully studied before using the equipment.
• The procedure for keeping the instrument within the box and taking it out should be carefully followed.
• The instrument should be protected from sun and rain by shading it with a field umbrella.
• While carrying an instrument from one place to the other it should be carried on the shoulder if the distance is short, pu otherwise it should be carried in its box.
•Donot set an instrument on smooth surfaces, to avoid spreading its tripod legs and finally falling of the instrument. In unavoidable circumstances, tripod legs should be inserted in the joints or cracks.
• Many telescopic instruments have lenses, which are damaged by moisture & dust. Proper care should be taken to keep them away from the moisture. Dust can be removed by applying lens cleaning liquid.
•While operating the foot screws and tangent screws, no excessive force should be used. They must be delicately handled.
• Donot leave the instrument on the roads, foot paths or in unguarded locations.