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Monday, June 13, 2011

precise traversing

precise traversing is theodolite traversing using more refined instruments and devices for linear and angular measurements.more advanced techniques are also used in field work.the theodolite used are special instrument such as the watt's wild,or zeiss theodolite. the accuracy attainable is at least 1 min of arc. its optical features are also superior. micrometer and double reading are invariably incorporated into these instruments. permanent adjustment are checked and ensured. for linear measurement ,a steel tape and steel band may be used ,and it is supported above the ground. the necessary correction have to be applied with due care.
regarding methods/techniques, the method in within included angels are measured at all stations is refereed. however the bearing of at least one of the sides of the traverse has to be measured with great accuracy so that the traverse is correctly oriented with respect to the north. a closed traverse is usually preferred so that all the relevant checks can be applied and closure ensured.
precise traversing is invariably conducted only under favourable atmospheric conditions, so that errors due to natural causes are minimised. the angular error of closure should not exceed "15 min under root N"
where N is the no of angles in the traverse. the limit of linear error recommended is in 10000 and in any case not more than 1 in 5000. precise traversing is primarily used to survey important boundaries, properties limits in urban areas where land acquisition costs are high, and in the location of important roads and railways. it is used only when triangulation is difficult as in the case of thickly wooded areas.

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