engleski

Determination of Temperature Extension Coefficient of Invar Levelling Staves

The determination of heights using the method of geometric levelling belongs to the most precise geodetic measurements. The majority of errors in geometric levelling can be eliminated in the most part by testing and rectification of instruments, by selecting an appropriate measuring method and the most convenient external conditions and the time of the day and the year. The errors that cannot be eliminated in filed conditions are the error of staff scale, the error of irregularly attached staff scale and the error of determining the temperature extension coefficient of invar levelling staff. These errors can be determined only by testing and calibration in the laboratory. There is a comparator for calibration of invar levelling staves and measuring tapes in the Laboratory for measurements and measuring techniques at the Faculty of Geodesy, University of Zagreb. The calibration of invar levelling staves implies the comparison of standard length and the length of operation scale. Special software interface in Visual Basic has been created for the automation of invar levelling staves calibration and measuring tapes on the comparator enabling the determination of temperature extension coefficient of invar apart from the calibration. The procedure of determining the temperature extension coefficient of three invar levelling staves originating from various manufacturers on the comparator in the Laboratory at the Faculty of Geodesy has been described in this work (centimeter graduation, 5 mm graduation and coded). For each of these levelling staves the measurements were made at the temperatures of approximately from 6 °C to 32 °C. In the precise geometric levelling it is necessary to correct the reading on the staff taking also the value of the temperature extension coefficient of invar levelling staff into consideration.

calibration; comparator; invar levelling staff; temperature extension coefficient of invar; geometric levelling

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