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Remote sensing of urban materials by their bidirectional reflectance distribution function
2009 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Remote sensing systems exploit optical properties to gain information about a target. In the majority of the cases, this is done by exploiting the spectral domain. Only little effort is spend on looking for alternatives. The idea, that is investigated in this study, is to take advantage of the bidirectional reflectance which may carry information about the type of material, of which the target is composed. This method may be interesting especially for urban regions, where targets with different inclinations and orientations are distributed on a small area. A camera, which views two targets of the same material receives different fluxes according to the inclination of each target. That can disturb a classification process that is based on spectral information only, and does not take into account bidirectional reflectances. As for spectral data, bidirectional reflectance data is available for many types of materials. However, data sets are mostly restricted to incidence and reflection zenith angles of 60°. Therefore, to start with, measurements are conducted to acquire data which covers the whole upper hemisphere of a sample, i.e. a solid angle of 2pi. For this first phase, the goniometer available at ONERA in Toulouse is used, which, as well, is restricted to 60° zenith angle. An inclination wedge is used in order to measure angles up to a zenith angle of 80°. Limitations of this method are found. Seven real-world urban samples have been measured respecting the limitations of the measurement method. They represent well the diversity of materials which can be found in a city. Surprinsingly, for some of the samples, measurements show an increase in reflectance in the forward direction for grazing zenith angles. Three of the seven data sets are fitted to recent successful BRDF models. A model which is able to successfully describe BRDFs of urban materials has not been found. However, the model developed by R.L. Cook and K.E. Torrance describes the above mentioned effect of increasing reflectance for grazing angle surprisingly well. It is considered to be a good candidate for further investigations on the way to establish a classification algorithm which is based on bidirectional reflectances.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Urban remote sensing, bidirectional reflectance distribution, function, BRDF, goniometer
Keyword [sv]
URN: urn:nbn:se:ltu:diva-55669ISRN: LTU-PB-EX--09/116--SELocal ID: c8232a58-b71a-4b00-985b-493db8f30646OAI: diva2:1029053
Subject / course
Student thesis, at least 30 credits
Educational program
Space Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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