Mapping of Asbestos Cement Roofs and Their Weathering Status Using Hyperspectral Aerial Images

Chiara Cilia,Micol Rossini,Roberto Colombo,Cinzia Panigada,Gabriele Candiani,Monica Pepe

doi:10.3390/ijgi4020928

Abstract

The aims of this study were: (i) the mapping of asbestos cement roofs in an urban area; and (ii) the development of a spectral index related to the roof weathering status. Aerial images were collected through the Multispectral Infrared and Visible Imaging Spectrometer (MIVIS) sensor, which acquires data in 102 channels from the visible to the thermal infrared spectral range. An image based supervised classification was performed using the Spectral Angle Mapper (SAM) algorithm. The SAM was trained through a set of pixels selected on roofs of different materials. The map showed an average producer’s accuracy (PA) of 86% and a user’s accuracy (UA) of 89% for the asbestos cement class. A novel spectral index, the “Index of Surface Deterioration” (ISD), was defined based on measurements collected with a portable spectroradiometer on asbestos cement roofs that were characterized by different weathering statuses. The ISD was then calculated on the MIVIS images, allowing the distinction of two weathering classes (i.e., high and low). The asbestos cement map was handled in a Geographic Information System (GIS) in order to supply the municipalities with the cadastral references of each property having an asbestos cement roof. This tool can be purposed for municipalities as an aid to prioritize asbestos removal, based on roof weathering status.

Highlights

The term “asbestos” is used to refer to a group of fibrous silicate minerals
In our study we propose a novel spectral indicator (i.e., Index of Surface Deterioration” (ISD), Index of Surface Deterioration) that is not directly related to the surfacing fibers, but rather related to the abundance of mosses and lichens that are reported to be more developed on older and weathered substrata [13]
Spectra collected on the ground and spectra extracted from the corresponding pixels of the Multispectral Infrared and Visible Imaging Spectrometer (MIVIS) images are reported in Figure 2a,b respectively

Summary

Introduction

The term “asbestos” is used to refer to a group of fibrous silicate minerals. Regulation is limited to six of these minerals, which only partially account for the existing, naturally-occurring fibers [1].Among these regulated minerals, chrysotile is part of the serpentines, while actinolite, amosite, anthopyllite, crocidolite and tremolite are part of the amphiboles. The term “asbestos” is used to refer to a group of fibrous silicate minerals. Regulation is limited to six of these minerals, which only partially account for the existing, naturally-occurring fibers [1]. Among these regulated minerals, chrysotile is part of the serpentines, while actinolite, amosite, anthopyllite, crocidolite and tremolite are part of the amphiboles. All of them are classified as “carcinogenic to humans” by the International Agency for Research on Cancer. The hazard of asbestos is due to the fibers that are released into the environment and inhalable. In case of asbestos cement (AC) roofs, the release is mainly due to weathering (i.e., rain, ice and wind)

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Results

Conclusion