Accuracy of waste stockpile volume calculations based on UAV Photogrammetry

R. Künnapuu¹*, K. Kokamägi² and N. Liba³

¹Ministry of the Environment, Environmental Management Department, Paldiski rd 96, EE13522 Tallinn, Estonia
²Estonian University of Life Sciences, Institute of Agricultural and Environmental Sciences, Chair of Environmental Protection and Landscape Management, Kreutzwaldi 5, EE51006 Tartu, Estonia
³Estonian University of Life Sciences, Institute of Forestry and Rural Engineering, Chair of Forest and Land Management and Forest Industry, Kreutzwaldi 5, EE51006 Tartu, Estonia
*Correspondence: raunokunnapuu@gmail.com

Abstract:

In environmental supervision, it is necessary to measure waste piles volume to determine whether the activities of the waste manager comply with the established requirements. The aim of this research is to determine whether the model, formed from images collected with low-priced unmanned aerial vehicle (UAV) – not with Real Time Kinematic Global Navigation Satellite System (RTK GNSS) capability – is sufficiently accurate to carry out waste-related surveying. Data collection took place in spring 2021 at the Aardlapalu transhipment station in Tartu County. The objects of the research were an unscreened composting pile and a covered composting pile. In the fieldwork, terrestrial laser scanning and photogrammetric flight were carried out. The reference value was the volume of the model formed from the data of laser scan. The volumes of all models formed by the photogrammetric method were within the permissible difference of 10% provided by law. The most accurate results were obtained from the covered composting pile with an overlap of 70% × 70% and 21 ground control points (GCPs). Using these parameters, the absolute error of the model was 1.48 m³ and the relative error was 0.65%. The most inaccurate results were obtained from the unscreened composting pile with an overlap of 80% × 80% and 21 GCP-s. The research confirmed the hypothesis that sufficient accuracy to calculate waste piles volumes can also be achieved by using a cheaper UAV and camera and with software not specially designed for photogrammetry, design, and drawing.

Key words:

3D modelling, digital image, ground control point, mean square error, photogrammetry

UAV photogrammetry for volume calculations

K. Kokamägi¹*, K. Türk² and N. Liba²

¹University of Life Sciences, Institute of Agricultural and Environmental Sciences, Chair of Environmental Protection and Landscape Management, Kreutzwaldi 5, EE51006 Tartu, Estonia
²Estonian University of Life Sciences, Institute of Forestry and Rural Engineering, Chair of Geomatics, Kreutzwaldi 5, EE51006 Tartu, Estonia
*Correspondence: kaupo.kokamagi@student.emu.ee

Abstract:

This research assesses the suitability of UAV (Unmanned Aerial Vehicle) photogrammetry for calculating stockpile volumes and analyses the compliance of the accuracy of results to current laws. In addition two different UAV’s and two different objects are compared and the necessity of using GCP’s (Ground Control Points) is investigated. The time spent on each work stage is also evaluated. Data used in this study was collected in two sites, where the objects differed in shape, colour and texture. The investigated objects were a regularly shaped peat stockpile and an irregularly shaped gravel stockpile. Data was collected with a terrestrial laser scanner, a GNSS (Global Navigation Satellite System) device and two different UAVs. Volume of the models calculated from different data was compared to the volume of the models based on laser scanning data for accuracy assessment. Relative errors of all of the photogrammetric models compared to the laser scanning based model were under 4%. It was concluded that the advantages of UAV based photogrammetry become apparent as the complexity and size of the measured objects grow. Results of the study show that using UAV photogrammetry to determine stockpile volumes is sufficiently accurate with both of the tested UAVs. The results show that without using GCPs (Ground Control Points), sufficient accuracy was still achieved. Nevertheless accuracy was increased by using GCP’s. It was concluded that using UAV’s can significantly reduce the time spent on collecting data for volume calculations, especially when GCP’s are not necessary.

Key words: