CoolPaths: Street-scale Physiological Equivalent Temperature (PET) mapping and cooler-routes planning using open data

Abstract

This study presents a fully automated pipeline for mapping Physiological Equivalent Temperature (PET) at high spatial resolution and simulating potential access to cooler paths for pedestrians in cities. PET quantifies the combined effect of solar and thermal radiation on humans and is key to assessing outdoor comfort. The pipeline automatically extracts building footprints, infers building heights, and computes shadows and sky-view factors. It uses Google Earth Engine to obtain tree canopy layers and other open-access satellite data products to compute vegetation, impervious surfaces, and water bodies, which help generate surface albedo maps. Solar irradiance, Mean Radiant Temperature (MRT), and PET maps are then created using meteorological inputs retrieved from the NASA POWER API. The generated maps are then fed into an OSM-based routing engine to identify shorter, cooler paths. This open-source tool can provide researchers, urban planners, and public health practitioners with relevant information to evaluate heat-mitigation strategies and design more comfortable, resilient outdoor spaces.