Evaluation and Implementation of Low Cost Unmanned Aerial Platforms for Rapid Geo-Spatial Data Collection in Pakistan’s Context

Abstract

Use of Geographic Information System in developing countries suffers from ‘data voids’ arising out of capacity and availability issues associated with space based remote sensing, aerial imaging and laser scanning. With advancements in digital imaging, navigation, electronics and computer-vision based photogrammetry, low cost Unmanned Aerial Platforms (UAPs) proffer a potential solution to overcome these ‘data voids’ at local scale. Objective of research is to evaluate and implement use of low cost UAPs for geo-spatial data collection in urban terrain using commercial off the shelf and open source technologies in Pakistan’s context. Research also explores related regulatory framework. After identifying potential hardware and software solutions through literature review, two low cost multi-rotor UAPs were acquired. These were used for acquisition of over-lapped vertical photographs of the selected study areas in main campus of National University of Sciences and Technology, Islamabad. Photographs were processed with ‘Structure from Motion’ algorithms based software. Initial results showed large positional inaccuracies in the generated data vis-à-vis surveyed Ground Control Points. These errors were traced to less precise geo-tagging by internal GPS of the camera. To rectify, a higher precision external GPS was subsequently used. Eight flights over the study area were conducted at a flying altitude of 70 ~ 90 meters above ground level. Over 1100 vertical photographs were processed into digital surface model, ortho-mosaics and 3D models achieving Ground Sampling Distance of 2.1 to 3 centimetres. Once evaluated for accuracy against surveyed GCPs, resultant data had a Root Mean Square Error within 0.5 in X, Y and 0.1 m in Z dimensions while solely relying on direct geo-referencing. Research identified issues related to processing of skeletal objects, occlusion and vegetation. With high resolution and high accuracy geo-spatial data produced at local scale, research demonstrated the utility and cost-effectiveness of UAPs against traditional methods. Research also established the requirement of realigning civil aviation regulatory framework for integrated use of UAPs in research and industry in Pakistan. Identifying immense scope for further application of these technologies in the field of urban planning, agriculture, environmental monitoring and disaster management, research recommends enhanced academic research on UAP technologies in Pakistan.