Comparative Assessment of the Accuracy of the Elevation differences obtained from different Geomatics Techniques and Instruments
This study carried out the comparative evaluation of the accuracy of elevation differences determined from two Geomatics instruments and techniques in part of University of Benin, Ugbowo Campus. Reconnaissance survey was carried out and the two Geomatics instruments (Total station instrument and the Automatic level instrument) used for this study were tested and found to be in good working conditions. In line with the survey regulation, the position of the control stations (UB GPS101and UB GPS102) where the survey commenced were checked for disturbance and the obtained angular and linear measurements proved that the control stations were in situ. The perimeter traversing, using the total station instrument, with closed traverse technique and the perimeter levelling using the trigonometric levelling method and the level instrument with flying level both commenced from the GPS control stations and terminated at the same control stations. The known coordinates of UB GPS102, when compared with those determined with the total station instrument, have some millimetres differences. The difference in the elevation of the GPS control station and the elevation determined for the same control station with the total station instrument was in millimetre. These values were within the specified and acceptable accuracy limits. The accuracy of the tertiary traverse survey, which has satisfied the allowable accuracy limits for tertiary traverse survey, was 1: 41,428.043. The allowable accuracy for third order levelling for the study area was 26mm. Their computed accuracies using the total station and level instruments were 21mm and 13mm respectively. Although the elevations determined from the two Geomatics instruments met the standard accuracy limits for tertiary levelling, the accuracy of the elevations obtained with the level instrument is higher than those obtained with the total station instrument. These results are in conformity with the findings of some researchers on the related subject matter.