This characteristic has been commonly used in studies to assess the degree of urbanization of an environment as well as explore the spatial extent of surface urban heat islands (Roy and Yuan 2009).The relationship between LST and vegetated areas has been documented in the literature. (1995) compared the spatial distribution of micro-urban heat islands and tree cover in Dallas, Texas, using L5-TM and geographic information systems (GIS).They examined the usefulness of L5-TM for classifying tree-cover information and using thermal band 6 to produce a thermal map of Dallas, Texas.
Although L5-TM data were useful for mapping micro-urban heat islands in Dallas, the authors recommended use of exact on-the-ground temperatures for image calibration in future studies.
Remote sensing data have been used to help model urban surface temperatures; specifically, validating LST data with actual on-the-ground temperature measurements, known as ground-truthing.
For example, strong correlations between satellite-derived air temperatures and measurements were found when characterizing urban heat island intensity in Hong Kong, using ASTER satellite imagery (Fung et al. Comparisons between ground temperatures and estimated temperatures using imagery from MODIS, the National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA-AVHRR), and L5-TM, showed a very high correlation in both urban and rural areas (Rigo et al. Although previous studies have used Landsat to create prediction models for surface temperature, and shown strong correlations between surface temperature and surface imperviousness (Yuan and Bauer 2007), few studies have simultaneously explored the relationship among SI, ground-based temperature measures, and LST calculated from thermal imagery.
The data captured by satellite can be transformed into several helpful measures, including land surface temperatures (LST) and percent surface imperviousness (SI).
LSTs are a primary factor in determining surface radiation and human comfort in cities (Weng 2009).
The higher spatial resolution of L5-TM information is important in micro-urban heat island studies, so we have focused on those data here.The SI is defined as the percent of the surface of an area that is not penetrable by water, such as concrete or asphalt, and can be mapped at a 30-m resolution with L5-TM.Use of thermal remote sensing and advanced spatial modeling are emerging trends in environmental epidemiology and public health.Geospatial technologies provide a valuable resource to assist public health practitioners and emergency response planners in identifying areas that are most at risk and using these scientific outputs to inform policies and practices.Thermal remote sensing products such as thermal images captured by the Landsat-5 Thermal Mapper (L5-TM) (NASA 2013) instrument have been used to study areas of higher relative temperatures within a city, also known as micro-urban heat islands (Johnson 2009).L5-TM has an advantage over other sensors, such as the Moderate Resolution Imaging Spectroradiometer (MODIS) (NASA 2011), in that L5-TM provides a spatial resolution of 120 m (compared with 1,000 m for the thermal band of MODIS); however, it provides only 16-day repeatability, at best, compared with 1-day repeatability for MODIS (Aniello et al. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is another sensor that could be used, but imagery is not available free of charge (NASA Jet Propulsion Laboratory 2012).