Application of UAV and GNSS Technologies in Topographic Mapping for Urban Management and Planning in Vietnam

Vietnam's rapid urban transition is generating an urgent demand for topographic information that is accurate, current, three-dimensional, and sufficiently detailed for planning, infrastructure management, construction control, environmental assessment, and disaster-risk reduction. Conventional total-station and leveling surveys remain indispensable for legal control networks and high-precision engineering tasks, but they are often too slow and spatially sparse to support frequent city-scale updating. This article examines the application of unmanned aerial vehicles (UAVs) integrated with Global Navigation Satellite System (GNSS) technologies for large-scale topographic mapping in support of urban management and planning in Vietnam. The study adopts an integrative evidence-synthesis approach, combining peer-reviewed empirical studies conducted in Vietnam, national legislation and technical regulations, official geodetic-infrastructure information, and international standards and research on UAV photogrammetry, direct georeferencing, LiDAR, and three-dimensional city models. Vietnamese case evidence shows that UAV-GNSS workflows can achieve centimeter- to decimeter-level positional accuracy under favorable conditions. A 165 ha survey in Thanh Son District produced a 1:2,000 topographic map from 590 images with a 2.3 cm ground sampling distance and reported northing, easting, and vertical errors of 1.8, 1.4, and 4.7 cm, respectively. A 40 ha construction-monitoring study in Ho Chi Minh City generated multi-epoch orthomosaics and digital surface models with root-mean-square errors below 10 cm. A 1:500 quarry survey reported horizontal and vertical errors below 8.2 and 10 cm and a 60% reduction in field time. These findings demonstrate strong technical potential, while also revealing limitations associated with vegetation, urban canyons, reflective roofs, occlusion, datum transformation, quality control, computing capacity, data governance, privacy, and flight authorization. The article proposes a standardized UAV-GNSS production workflow, an accuracy-based decision framework, a governance architecture, and a phased implementation roadmap for Vietnamese cities. It concludes that UAV-GNSS mapping should be institutionalized as a complementary component of the national geospatial data infrastructure rather than treated as a stand-alone replacement for conventional surveying. The greatest value will arise when high-resolution UAV products are linked to authoritative control networks, cadastral and planning databases, Building Information Modeling, web GIS, and open geospatial standards.