Building roof extraction as data for suitability analysis

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ORIGINAL PAPER

Building roof extraction as data for suitability analysis A. K. Adeleke 1

&

J. L. Smit 1

Received: 11 June 2019 / Accepted: 26 April 2020 # Società Italiana di Fotogrammetria e Topografia (SIFET) 2020

Abstract The geographic potentials of building roofs in urban areas are often under-utilized or sometimes neglected entirely. This is due to the lack of large-scale building roof inventory in the municipality planning offices in African cities. Building rooftops offer great potentials in addressing key urbanization problems such as suitability analysis, disaster management, and others. This paper seeks to demonstrate how remote sensing techniques can be applied to detect and extract building roofs for various suitability analyses (e.g., solar energy and rainwater harvesting) by developing a unique two-in-one technique, which detects and extracts building roof planes and building roof outlines. Using the City of Cape Town, South Africa, as a case study, building rooftops were extracted using the integration of light detection and ranging (LiDAR) data and aerial imagery in an object-based rule-set classification process. This resulted in a building roof inventory, which has crucial attributes of evaluating a building roof for various suitability analyses. The technique developed is well suited for residential and industrial areas where buildings are easily separated from each other. The method and the extracted results were accessed for accuracy and were found to compare well with similar methods already benchmarked. Keywords Urban extraction . Suitability analysis . Object-based classification . Data fusion

Introduction A greater proportion of the world’s population now resides in cities and urban areas, thereby putting a strain on the ecological footprint in urban areas. This has led countries to look for ways to improve or achieve sustainability in urban areas, as well as reducing their ecological footprint (UN Department of Economic and Social Affairs 2013). Some of the United Nation’s seventeen sustainable development goals focus on achieving sustainability in urban areas, as well as the provision of clean energy and water (UN General Assembly 2015). Building rooftop spaces offer potentials, which can be harnessed in achieving the desired sustainability. Such potentials include provision of spaces for rainwater harvesting and installation of solar photovoltaic panels for electricity generation. However, not all building roofs in an urban area would be

* A. K. Adeleke [email protected] 1

Geomatics Division, School of Architecture, Planning and Geomatics, University of Cape Town, Private Bag X3, Rondebosch 7700, South Africa

able to offer an efficient potential for solar or rainwater harvest, thereby bringing about the need for a suitability analysis. Suitability analysis involves assessing various properties or attributes of a place or site intended for accommodating a project. These attributes of the site are analyzed in the form of multicriteria analysis, with weights assigned to each,