Abstract
Knowledge about the existing materials in urban areas has, in recent times, increased in importance. With the use of imaging spectroscopy and hyperspectral remote sensing techniques, it is possible to measure and collect the spectra of urban materials. Most spectral libraries consist of either spectra acquired indoors in a controlled lab environment or of spectra from afar using airborne systems accompanied with in situ measurements. Furthermore, most publicly available spectral libraries have, so far, not focused on facade materials but on roofing materials, roads, and pavements. In this study, we present an urban spectral library consisting of collected in situ material spectra with imaging spectroscopy techniques in the visible and near-infrared (VNIR) and short-wave infrared (SWIR) spectral range, with particular focus on facade materials and material variation. The spectral library consists of building materials, such as facade and roofing materials, in addition to surrounding ground material, but with a focus on facades. This novelty is beneficial to the community as there is a shift to oblique-viewed Unmanned Aerial Vehicle (UAV)-based remote sensing and thus, there is a need for new types of spectral libraries. The post-processing consists partly of an intra-set solar irradiance correction and recalculation of reference spectra caused by signal clipping. Furthermore, the clustering of the acquired spectra was performed and evaluated using spectral measures, including Spectral Angle and a modified Spectral Gradient Angle. To confirm and compare the material classes, we used samples from publicly available spectral libraries. The final material classification scheme is based on a hierarchy with subclasses, which enables a spectral library with a larger material variation and offers the possibility to perform a more refined material analysis. The analysis reveals that the color and the surface structure, texture or coating of a material plays a significantly larger role than what has been presented so far. The samples and their corresponding detailed metadata can be found in the Karlsruhe Library of Urban Materials (KLUM) archive.
Highlights
Assessment of materials in urban areas has in recent times increased in importance for several reasons
An additional processing step must be added for the reference spectrum E0 since we discovered that the signal had been cut off for several samples due to signal clipping
We present the material classification scheme that we created to suit a more refined categorization and an overview of the material classes and subclasses that are available in our spectral library, Karlsruhe Library of Urban Materials (KLUM) (Section 4.1)
Summary
Assessment of materials in urban areas has in recent times increased in importance for several reasons This knowledge is useful for city planners and researchers while working with city models or simulations where the need for a high level of detail about the buildings, which can include the materials, is important. Hyperspectral data is often used for classification due to the broad wavelength range (e.g., 350–2500 nm) It is suitable for urban material classification [18,19] as hyperspectral data can ease the distinction of characteristic spectral features due to the large spectral range. Another advantage of hyperspectral data as opposed to multispectral, which consists of spaced spectral ranges, is that hyperspectral data allows the use of gradient calculations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
