Evaluation of satellite-derived building height extraction by CFD simulations: A case study of neighborhood-scale ventilation in Hong Kong

Abstract Computational fluid dynamics (CFD) techniques, such as large-eddy simulation (LES), are widely used in urban ventilation studies. Unfortunately, realistic building data required in CFD studies are not always available. In this study, LES of urban ventilation is used to assess building height extraction from different satellite images. As a case study, three sets of digital elevation data extracted from satellite images in an urban area of Mong Kok, Hong Kong, are assessed. Simulations of velocity ratio from the LES model are first validated by wind tunnel measurements, yielding a recommended local roughness length of 0.02 m. Wind characteristics in urban elevations extracted from two single satellite images and the fused result are then compared with those from realistic data in the same area, using identical LES settings. It is found that building height data retrieved from the WorldView-2 optical (stereo) images are of poor quality, as they underestimate higher buildings, which are deemed to be more important for pedestrian-level velocity ratios. The TerraSAR-X synthetic aperture radar (SAR) image and the fused results of SAR and stereo images are sufficient for CFD simulations of urban ventilation. This fusion provides a slight improvement over SAR images alone in reproducing urban geometric parameters, and it is superior in simulating more accurate wind profiles in the urban canopy.

[1]  Edward Ng,et al.  Urban climatic map studies: a review , 2011 .

[2]  E. Johansson,et al.  Influence of urban morphology and sea breeze on hot humid microclimate: the case of Colombo, Sri Lanka , 2006 .

[3]  Jin Duan,et al.  Assessment of pedestrian wind environment in urban planning design , 2015 .

[4]  Siegfried Raasch,et al.  A Large-Eddy Simulation Study of Thermal Effects on Turbulent Flow and Dispersion in and above a Street Canyon , 2012 .

[5]  Manabu Kanda,et al.  The Effects of Inner- and Outer-Layer Turbulence in a Convective Boundary Layer on the Near-Neutral Inertial Sublayer Over an Urban-Like Surface , 2011 .

[6]  Manabu Kanda,et al.  Large-Eddy Simulation of Coherent Flow Structures within a Cubical Canopy , 2012, Boundary-Layer Meteorology.

[7]  Hui Lin,et al.  Fusion of WorldView-2 Stereo and Multitemporal TerraSAR-X Images for Building Height Extraction in Urban Areas , 2015, IEEE Geoscience and Remote Sensing Letters.

[8]  Edward Ng,et al.  Large-eddy simulations of ventilation for thermal comfort — A parametric study of generic urban configurations with perpendicular approaching winds , 2017 .

[9]  Mats Sandberg,et al.  Numerical and experimental studies of wind environment in an urban morphology , 2005 .

[10]  Sandra Eckert,et al.  Comparison of Automatic DSM Generation Modules by Processing IKONOS Stereo Data of an Urban Area , 2010, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing.

[11]  V. Cheng,et al.  Urban human thermal comfort in hot and humid Hong Kong , 2012 .

[12]  Siegfried Raasch,et al.  PALM - A large-eddy simulation model performing on massively parallel computers , 2001 .

[13]  E. Ng.  Policies and technical guidelines for urban planning of high-density cities – air ventilation assessment (AVA) of Hong Kong , 2008, Building and Environment.

[14]  Edward Ng,et al.  Improving the wind environment in high-density cities by understanding urban morphology and surface roughness: A study in Hong Kong , 2011, Landscape and Urban Planning.

[15]  Nicolas Trouve,et al.  Performance of Building Height Estimation Using High-Resolution PolInSAR Images , 2014, IEEE Transactions on Geoscience and Remote Sensing.

[16]  János Unger,et al.  Intra-urban relationship between surface geometry and urban heat island: review and new approach , 2004 .

[17]  A. Arnfield.  Two decades of urban climate research: a review of turbulence, exchanges of energy and water, and the urban heat island , 2003 .

[18]  J. Tukey,et al.  Variations of Box Plots , 1978 .

[20]  Xiang Zhou,et al.  Seamless Fusion of LiDAR and Aerial Imagery for Building Extraction , 2014, IEEE Transactions on Geoscience and Remote Sensing.

[21]  M. Kanda,et al.  A New Aerodynamic Parametrization for Real Urban Surfaces , 2013, Boundary-Layer Meteorology.

[22]  E. Ng,et al.  Urban heat islands in Hong Kong: statistical modeling and trend detection , 2016, Natural Hazards.

[23]  Bert Blocken,et al.  CFD simulation of outdoor ventilation of generic urban configurations with different urban densities and equal and unequal street widths , 2015 .

[24]  Studies on wind environment around high buildings in urban areas , 2005 .

[25]  Hui Lin,et al.  Urban morphology detection and computation for urban climate research , 2017 .

[26]  Feng Yang,et al.  Urban form and density as indicators for summertime outdoor ventilation potential: A case study on high-rise housing in Shanghai , 2013 .

[27]  R. Britter,et al.  FLOW AND DISPERSION IN URBAN AREAS , 2003 .

[28]  Florence Tupin,et al.  Extraction and Three-Dimensional Reconstruction of Isolated Buildings in Urban Scenes From High-Resolution Optical and SAR Spaceborne Images , 2011, IEEE Transactions on Geoscience and Remote Sensing.

[29]  Siegfried Raasch,et al.  The Parallelized Large-Eddy Simulation Model (PALM) version 4.0 for atmospheric and oceanic flows: model formulation, recent developments, and future perspectives , 2015 .

[30]  Tetsuro Tamura,et al.  Towards practical use of LES in wind engineering , 2006 .

[31]  Jong‐Jin Baik,et al.  Large-Eddy Simulations of Convective Boundary Layers over Flat and Urbanlike Surfaces , 2014 .

[32]  F. Lindberg,et al.  Continuous sky view factor maps from high resolution urban digital elevation models , 2010 .

[33]  Edward Ng,et al.  A study of the " wall effect" caused by proliferation of high-rise buildings using GIS techniques , 2011 .

[34]  Edward Ng,et al.  LES case study on pedestrian level ventilation in two neighbourhoods in Hong Kong , 2012 .

[35]  Joel H. Ferziger,et al.  Status of Large Eddy Simulation: Results of a Workshop , 1997 .

[36]  Aya Hagishima,et al.  Analysis of airflow over building arrays for assessment of urban wind environment , 2013 .

[37]  Michael Schatzmann,et al.  Issues with validation of urban flow and dispersion CFD models , 2011 .

[38]  M. Letzel,et al.  High resolution urban large-eddy simulation studies from street canyon to neighbourhood scale , 2008 .

[39]  Curt H. Davis,et al.  Automated Building Extraction from High-Resolution Satellite Imagery in Urban Areas Using Structural, Contextual, and Spectral Information , 2005, EURASIP J. Adv. Signal Process..