Best Practices in Low Altitude UAV Mapping for GIS Applications

Abstract

Aerial data collection for use in GIS has, in the past, been an expensive undertaking and required significant capital expenditures for metric aerial cameras, aircraft purchase, maintenance, fuel, insurance, and not to mention a significant cost for specialized labour. The advent of Unmanned Aerial Vehicles (UAV’s), and their increasing mainstream use, has created an alternative to conventional aerial photography for the creation of Digital Surface Models (DSMs) and orthophotos. The standards of traditional aerial data collection have been spelt out in long-established guidelines by the American Society of Photogrammetry and Remote Sensing. UAV operators, often non-specialist newcomers to the field, have side-stepped these standards and have no means to ensure the quality and reproducibility of their data. I propose a set of simple best-practices that can be adopted both by UAV operators and their clients to establish some measure of Quality Assurance and Quality Control while maintaining the cost-advantage afforded by UAVs. These practices can be grouped into five main areas: 1) proper camera and lens selection, 2) pre-calibration of cameras used for photogrammetric mapping, 3) establishing accurate ground-control across the area of mapping and not relying on consumer-grade GNSS for air stations, 4) pre-flight calculation of flight parameters based on a clear accuracy requirement, 5) flying at a sufficient height to minimize relief displacement so as to create artifact-free orthophotos. It is hoped that a better understanding of the underlying principles of photogrammetry by both UAV operators and their clients will guarantee the proper implementation of UAVs for high-accuracy GIS data collection in the future.