Study on royalty for Sri Lankan quarry mining of industrial minerals using photogrammetric 3D modelling

Abstract

Royalty is a payment made to the owner of mineral rights for the privilege of extracting minerals from the ground on a lease agreement. Globally, there are three main methods used for the royalty calculation; namely unit based, value based and profit based methods. A combination of unit and value based systems is practised in Sri Lanka. However, an explosive based equation without any scientific base is adopted for the determination of excavated quantities of some minerals. The main objective of this study was to find an accurate method to calculate excavated quantity of a rock for calculation of royalty for industrial minerals in Sri Lanka. Initially, a multiple-borehole blast was carried out in a selected 'A Grade' quarry. A total station survey and an Unmanned Aerial Vehicle (UAV) survey were conducted to determine the excavated rock volume. The collected aerial photographs for photogrammetric 3D modelling were processed using Agisoft PhotoScan, Bentley ContextCapture and Drone Deploy softwares. The accuracy of each method was determined by comparing each estimated depleted volume with the value obtained from weighing the blasted tonnage. Photogrammetric 3D modelling gave the least deviation from the actual volume.