Multi-spectral Data Acquisition and Processing Techniques for Damage Detection on Building Surfaces

This paper describes the development and investigation of a multi-spectral laser scanner for non destructive diagnosis of damages on building surfaces. The application of four semiconductor lasers as defined active light source, especially in infrared wavelengths, allows the detection of damages like moisture, salt blooming and biological covering. Different methods for the evaluation of multispectral data for the analysis of damaged facades will be given. Whereas for preliminary statements vegetation and moisture indexes are applicable, further analysis is based on unsupervised and supervised pixel-based classification as well as object-oriented classification methods. An example clearly demonstrates the successful application of the multi-spectral laser scanner for the measurement of the relative moisture distribution on masonry. Additionally, different evaluations based on multi-spectral imagery from digital and infrared cameras (Vidicon) show the capabilities of multi-spectral techniques for the detection of damages on building surfaces.