Comparative Analysis of Drone-Based and GNSS Surveys in Urban Land Mapping

Thesis Abstract

Urban land mapping is critical for sustainable development, urban planning, and resource management; however, the increasing demand for accurate, cost-effective, and timely geospatial data has led to the exploration of various surveying methodologies. Traditional ground-based GNSS (Global Navigation Satellite System) surveys are widely used but often face challenges related to accessibility, obstructions, and extended data acquisition times in complex urban environments. Conversely, drone-based photogrammetric surveys have emerged as a promising alternative, offering high-resolution data capture and operational flexibility. Nonetheless, comparative evaluations of these methodologies in dense urban settings remain limited, necessitating rigorous analysis to inform best practices. The primary aim of this study is to conduct a comprehensive comparative analysis of drone-based surveys and GNSS-based terrestrial surveys in urban land mapping, examining their positional accuracy, efficiency, cost implications, and operational feasibility within a distinct urban context. Specific objectives include (1) assessing the positional accuracy of drone-derived orthomosaics against GNSS survey data; (2) evaluating the time and cost efficiency of both methods; (3) analyzing the operational challenges encountered during survey implementations; and (4) providing recommendations for optimal methodology selection in urban land mapping projects. The study adopts a mixed-methods research design, integrating quantitative and qualitative approaches. The quantitative component involves a cross-sectional survey of twenty urban sites with varied complexities, selected through stratified random sampling from the central business district of a metropolitan city. Data collection employs high-resolution drone imagery captured using a DJI Phantom 4 Pro equipped with RTK capabilities, and GNSS surveys conducted with Trimble R10 GNSS receivers, following established cadastral survey procedures. The sample size of 200 surveyed points per method ensures statistical robustness. Validation of data involves the use of differential GPS correction data and ground control points, with positional accuracy analyzed through root mean square error (RMSE) calculations and statistical tests such as paired t-tests and ANOVA to compare the methods. Data analysis will employ Geographic Information System (GIS) software for spatial data processing, along with regression analysis to examine factors influencing accuracy. Thematic analysis of qualitative operational challenges will be conducted using NVivo software to identify common issues and success factors. Ethical considerations include obtaining necessary permits, ensuring data confidentiality, and adherence to safety protocols during drone operations. Expected findings include that drone-based surveys will yield comparable positional accuracy (RMSE less than 10 cm) to GNSS surveys in open areas but may be less accurate in obstructed environments due to signal interference. Drone surveys are anticipated to demonstrate higher operational efficiency, reducing total survey time by approximately 30% and lowering costs by up to 25%. However, challenges such as regulatory restrictions, airspace management, and technical limitations in dense urban areas are expected to be significant, requiring tailored operational protocols. This research will contribute new insights into the relative strengths and limitations of drone-based versus GNSS survey techniques in complex urban environments, filling existing empirical gaps. It proposes a framework for context-specific methodology selection, emphasizing practicality, accuracy, and cost-effectiveness. The main conclusion underscores that while drone surveys are promising for rapid urban mapping, their deployment must be carefully managed considering local regulatory frameworks and environmental conditions. Based on findings, it is recommended that urban land mapping projects adopt an integrated approach, utilizing drone surveys complemented by GNSS or terrestrial surveys for critical accuracy requirements, and that policymakers refine UAV operation regulations to facilitate safer and more efficient urban applications. The study’s outcomes will serve informants for geospatial practitioners, urban planners, and policymakers aiming to optimize urban land mapping practices amid technological advancements.