What's Up On The Roof: Tracking Cool Roofs in India with Satellite Imaging

Abstract

With rapid pace of urbanization, the increase in built up area is leading to urban heat islands which absorb a lot of the heat received through solar radiation. To reduce this effect, reflective coatings on top of building roofs, known as cool roofs are installed. Cool roofs reflect light back through the atmosphere to minimize the heat radiation within the urban space. In this paper, we introduce a cool roof tracker. The tracker provides building level information of whether a roof is cool or not, thus indicating if an urban heat island is likely to develop in a region. This information helps policymakers identify the vulnerable regions in a city and track the progress of cool roof implementation in all areas. There are three key components of the system: building polygon extraction, reflectance features extraction from roof images; and classification into cool vs non cool buildings. There are a number of satellites operational today which offer different strengths - high resolution, high revisit time, multiple spectral bands, etc. In this work, we do a mix of quantitative and qualitative evaluation of the efficacy of different satellite modalities for each of the system components, build robust models with extensive experimentation on color space, augmentations, and generalization achieving an F1-score of 97% on our test set. We also develop a prototype dashboard as a demonstration for supporting data-driven decision making for state level heat mitigation plans as well as regulatory and compliance tool for measuring roof reflectance.