Guidelines for Accurate Surveying

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Surveying, Even though it is of diverse nature, there are some basic guidelines which are common to all branches of surveying. These guidelines have proved over the years to be vital if accurate surveys are to be conducted.

Guidelines for Accurate Surveying

There are four most important guidelines which are to be followed to get accurate results of surveying.

1. Initial Framework
2. Planning
3. Checking
4. Safeguarding

1. Initial Framework

Providing initial framework before spotting and setting the detail of a survey is the vital guideline of accurate surveying. The framework of survey means establishment of control points and subsidiary points. The control points should be established with higher accuracy than subsidiary points. By fulfilling this guideline, accumulation of inevitable errors can be eliminated and the occurred errors can be controlled within the framework. This process is also called as providing control.

2. Planning

Planning is the second most important guideline of surveying. Most of the surveys are conducted without proper planning which results uneven effects on the cost of the project. In surveying cost and accuracy relationship is not linear. For example, if a length of 500 m is to be determined to an accuracy of either 5 mm or 0.5 mm, the cost ratio of respective accuracies may be the order of 1:300. Hence, increase in accuracy will have unbalanced effects on cost. With proper planning, one can choose required techniques, proper instruments for survey. By careful observation of the area, most suitable method for given topography can also be known. These all comes under planning. Time spent on planning and reconnaissance is never wasted.

3. Checking

To eliminate or minimize the errors, sufficient independent checks at every stage of surveying is recommended. Every stage refers from field work to the final plotting. Checking means not only taking repeated measurements of the given line or area but also applying cross checks. The checking system should be independent and involved at all stages of surveying. Some examples of independent checks are as follows. Fieldwork Checking

• Check the distance of lines in both directions.
• Measure angles using theodolite
• Measure the diagonals of a quadrilateral.

Computation Checking

• Summation check on angle observations of formed geometrical figure of area. For example summation of interior angles equal to (2n-4) x 90^o.
• Apply cross checks for levelling measurements.

Final Plotting Check

• Using angles and distances plot the important points of survey also use co-ordinates for accurate position of points.

4. Safeguarding

Safeguarding measurements, field observations and survey markers is another important guideline to be noted. Every survey point established is marked with respect to the permanent reference or witness point within the vicinity of that marked point. If by any chance marked point is damaged or missed from the observation, then this reference points will help to find an established point. This situation arises mainly in road surveys where there is big gap between initial survey and final setting out. The permanent survey points marked in this surveys may become overgrown with vegetation and difficult to locate.  In this situation reference points play crucial role to reestablish the permanent survey points. Field observations should also be safeguarded by maintaining field book. Field book is used to record the observations at every stage. Major results of surveying like rounds of angles, mean distance etc. can be calculated by summarizing the abstract sheets of field book. The field book should be stored carefully. Read also: Surveying Principles and Methods in Civil Engineering