In surveying work the designation of straightness of elongated objects is done by method of constant straight, which requires an instrument setup over a given point. For the implementation of this task, you can use a plummet properly rectified. The minimum length to the target is a characteristic parameter of each instrument. This value limits location of the measurement points. In the conditions prevailing on the engineering objects it is often not possible to offset the instrument from the test object. At that time the first measurement points can be measured only after setting the instrument at the final point of constant straight. The method presented in this paper to measure the position of points relative to a specific fixed straight uses a light beam emitted by a laser plummet from a Leica TC407 total station. To use laser the beam of the plummet to measure points located at distances from zero to several meters from the position of the instrument by constant straight method additional instrumentation was applied. The additional equipment includes: collimating mirror, CCD adapter and computer. Preliminary research showed that for distances of 1, 2, 4, 8 and 12 m measuring points on the instrument were obtained respectively from 0.03 to 0.08 mm.

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