Comparison of UAV photogrammetry and conventional GNSS in the estimation of road construction earthworks.

Abstract

The efficiency of volumes determined in various fields of survey; mining, quarry, hydrographic and engineering fields can’t be overemphasized. Conventional surveying method using GNSS has been the most used for volume determination in surveying over the years, despite its long, risky and laborious data collection in sites. Even though, the Unmanned Aerial Vehicle as a platform has been an alternative in surveying, there have been doubts about its efficiency and accuracy. This project compared the applications of two novel surveying technologies of UAV and GNSS data collection platforms for earthwork volume estimation and also compared time spent employing the methods for data collection. For this purpose, an appropriate area (specified chainages) along Busega-Mpigi express way was chosen, two sets of observations were taken. First, the area was mapped by a UAV flight, and secondly measured using a GNSS. Pix 4D Mapper image processing software was used. The results have been analyzed with respect to differences in volumes and project time between the methods for data collection. After detailed analysis and comparison, it was found that both methods yield better and accurate results making both methods comparative for earthwork volume measurement. It was also realized that for this project, GNSS volume differs with that of the actual volume with 2.93% compared to UAV that showed a -0.54%. Consequently, it was also observed that using conventional surveying methods such as GNSS surveying volume estimation is more time consuming and the results are more generalized than using UAV technology where capturing thousands of surface points (i.e., point cloud) takes just seconds. In conclusion, the results show a promising future for UAV in volume estimation and surveying