Satellite Image Fusion to Detect Changing Surface Permeability and Emerging Urban Heat Islands in a Fast-Growing City

Abstract

Rapid and extensive urbanization has adversely impacted humans and ecological entities in the recent decades through a decrease in surface permeability and the emergence of urban heat islands (UHI). While detailed and continuous assessments of surface permeability and UHI are crucial for urban planning and management of landuse zones, they have mostly involved time consuming and expensive field studies, and single sensor derived large scale aerial and satellite imageries. We demonstrated the advantage of fusing imageries from multiple sensors for landuse and landcover (LULC) change assessments as well as for assessing surface permeability and UHI emergence in Tirunelveli, Tamilnadu, India. Cartosat-2 and Landsat-7 ETM+ imageries from 2007 and 2017 were fused and classified using a Rotation Forest (RF), while surface permeability and temperature were quantified using Soil-Adjusted Vegetation Index (SAVI) and Land Surface Temperature (LST) index, respectively. Fused images exhibited higher classification accuracies than non-fused images, i.e. overall kappa coefficient values 0.83 and 0.75, respectively. We observed an overall increase of 20 km2 (45%) in the coverage of urban (dry, real estate plots and built-up) areas, while a decrease of 27 km2 (37%) for vegetated (cropland and forest) areas in Tirunelveli between 2007 and 2017. The SAVI values indicated an extensive decrease in surface permeability for Tirunelveli overall (0.4) and also for almost all LULC zones. The LST values exhibited an associated overall increase (1.30C) of surface temperature in Tirunelveli with the highest increase (2.40C) for urban built-up areas between 2007 and 2017. The SAVI-LST combined metric depicted the Southeastern built-up areas in Tirunelveli as a potential UHI hotspot, while a caution for the Western riparian zone for UHI emergence in 2017. Our results provide important metrics for surface permeability and UHI monitoring, and inform urban and zonal planning authorities about the advantages of satellite image fusion.

Using Spatial Context and Demographic Analysis to Assess Surface Permeability in Philadelphia

“…A wide variety of remote sensing techniques have been applied to surface permeability research in urban and suburban settings. Many indices have been developed to identify permeable land characteristics, such as vegetation, in remotely sensed imagery (Labib & Harris, 2018;Okujeni et al, 2018;Padmanaban et al, 2019;Taramelli et al, 2019).…”

Urban Change Pattern Exploration of Megacities Using Multitemporal Nighttime Light and Sentinel-1 SAR Data

“…socio-economic changes within megalopolises [13,14], however they only focused on urban extent monitoring and urban land use transformation using multispectral and nighttime light data. Although fusion techniques have been already employed in urbanization monitoring using heterogeneous data sets of different resolutions and modalities [15,16,17], there is still no work related to the use of synthetic aperture radar (SAR) data in conjunction with other sensors. SAR data provides useful hints about physical changes to the bi-and threedimensional structure of the cities.…”

Improved water quality mapping based on cross‐fusion of Sentinel‐2 and Landsat‐8 imageries

“…Their results showed high improvement in the classification in comparison with the state‐of‐the‐art fusion methods. The advantage of fusing IRS‐LISS III and Landsat‐7 ETM + images were demonstrated in [20] for land use and land cover change assessments and also for assessing surface permeability and temperature and urban heat islands (UHIs) emergence in Tirunelveli, Tamil Nadu, India. Their results offer important metrics for surface permeability, temperature and UHI monitoring, and advise urban and zonal planning authorities about the benefits of satellite image fusion.…”