Dasymetric Mapping Using UAV High Resolution 3D Data within Urban Areas

Rebelo Rebelo,Tenedório Tenedório,Rodrigues Rodrigues

doi:10.3390/rs11141716

Abstract

Multi-temporal analysis of census small-area microdata is hampered by the fact that census tract shapes do not often coincide between census exercises. Dasymetric mapping techniques provide a workaround that is nonetheless highly dependent on the quality of ancillary data. The objectives of this work are to: (1) Compare the use of three spatial techniques for the estimation of population according to census tracts: Areal interpolation and dasymetric mapping using control data—building block area (2D) and volume (3D); (2) demonstrate the potential of unmanned aerial vehicle (UAV) technology for the acquisition of control data; (3) perform a sensitivity analysis using Monte Carlo simulations showing the effect of changes in building block volume (3D information) in population estimates. The control data were extracted by a (semi)-automatic solution—3DEBP (3D extraction building parameters) developed using free open source software (FOSS) tools. The results highlight the relevance of 3D for the dasymetric mapping exercise, especially if the variations in height between building blocks are significant. Using low-cost UAV backed systems with a FOSS-only computing framework also proved to be a competent solution with a large scope of potential applications.

Highlights

In the urban planning of small areas, their characterization and analysis precedes the drafting of intervention proposals
The error associated with each parameter was calculated, using as benchmark accurate vector data acquired by photogrammetric restitution, which included building footprint or building boundary on the ground (Figure 8) and elevations for each building (Figure 6)
The building block area extracted from the unmanned aerial vehicle (UAV) point cloud was overestimated for every building block, because the building blocks extracted include some elements at the rooftop, which were not included in the photogrammetric restitution—used for benchmarking, such as the top of outdoor balconies on the top floor

Summary

Introduction

In the urban planning of small areas, their characterization and analysis precedes the drafting of intervention proposals. The aforementioned urban analysis requires updated information, both for the spatial distribution of the population and for residential buildings This is a common practice of urban planners and urbanists. The geometry of these census tracts has been found to change between two censuses, either by spatial aggregation or by spatial disaggregation This aggregation or spatial disintegration occurs especially when new structures are built or when urban densification processes occur. Urban planners and urbanists can perceive the evolution of the population in these urban areas This evolution of the population is useful to study enclosures, lost spaces, public spaces, proximity, contiguity and urban density [1]. In this context, dasymetric mapping using different geometrical schemes and different types of information becomes useful [2,3,4]

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Conclusion