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Generation of urban objects spectral database using laboratory hyperspectral imager in Kaunas city (Lithuania)

Abstract : Urban territories are composed by a large panel of geographic objects characterising the socio-economics uses, the urban structures, urban and architectural spaces, dynamics, evolutions and transformations of the cities. Mineral urban objects as the built-ups, blocks, houses, industrial zones, commercial centres, streets, roads, etc., or vegetal as gardens, parks, etc., are results of modes of lifestyles, societal conceptualisation or uses of the geographic space. Complexity, heterogeneity, and multiplicity of the geographic objects are the footprints of the models of territorialisation and urban management. The gradient of spectral and geometric mosaics detected by the hyperspectral sensors are measuring urban structures’ and geographic objects organising the territories. Hyperspectral airborne imagers are proposing some promising monitoring systems for the characterisation of the cities. Spectral formalisation and systematisation of the urban objects detected are the necessary first step to develop tools for urban management. Cataloguing and generation of a spectral database over the city of Kaunas (Lithuania) is the first phase. The spectral database will be used to characterise precisely the urban objects, according to their spectral reflectance. Each urban object is defined by a number of typical spectra. The spectral Library generated, the Kaunas Urban Spectral Library (KUSL), was created in the framework of the ANR HYEP (HYperspectral imagery for Environnemental urban Planning) following two parts: an objects collection of Kaurna's city, and Laboratory hyperspectral measurements made at Aleksandras Stulginskis University. The KUSL spectral library contains the spectral signatures of urban objects collected over the city of Kaunas in July 2015, the samples collection and spectral measurements were done between the 21 of July and the 27 of July 2015. The average temperature during the campaign was equal to 17.5° Celsius, the average moisture content was equal to 67%. The materials sampling campaign concerned three districts of Kaunas: Kaunas center, Raudonvaris and Ringaudai districts. The database includes a variety of common urban materials that can be found in urban context; roofing, roads, vegetation and bare soils. The spectral measurements were done in a black room using the hyperspectral Themis-Vision VNIR400H imaging camera. The sensor was developed by the NASA Themis Vision Systems. The camera is able to measure the electromagnetic radiation from 400 nm to 1000 nm using 1024 narrow bands; the spectral resolution is equal to 0.6 nm. The CCD sensor has a pixel size of 6.45 µm and a framing rate of 20 MHZ, with a dynamic range of 12 bits. This configuration gives a matrix grid of 1392 x 1000 pixels in terms of image resolution. The lens field of vision is 30 degrees. The “KUSL” includes non-shadowed and shadowed spectra. The spectral measurements were done in laboratory, under artificial light. Depending on the samples disposal and form, some shadowed zone could be cleared, in that case, the shadowed spectral signatures were extracted in addition to the non-shadowed ones; five signatures were extracted for each object. For each object, five spectral measurements were acquired. In addition to the ASCII file containing the spectral measurements we have access to a second ASCII file containing statistics about the spectral measurements: Maximum, Minimum, Standard deviation, etc. It is completed by sample description files about the objects and the measurements conditions. The “KUSL” is planned to be an open spectral library, which could be used by the scientific community. 32 urban objects have been spectrally characterised on a total of 57 objects including the shadowed.
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https://hal-amu.archives-ouvertes.fr/hal-01819945
Contributor : Sébastien Gadal <>
Submitted on : Thursday, June 21, 2018 - 10:31:00 AM
Last modification on : Wednesday, October 14, 2020 - 4:25:05 AM

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  • HAL Id : hal-01819945, version 1

Citation

Walid Ouerghemmi, Sébastien Gadal, Gintautas Mozgeris, Vytautė Juodkienė, Donatas Jonikavičius, et al.. Generation of urban objects spectral database using laboratory hyperspectral imager in Kaunas city (Lithuania). 4ème colloque du Groupe Hyperspectral de la Société Française de Photogrammétrie et Télédétection (SFPT-GH), Institut polytechnique de Grenoble, May 2016, Grenoble, France. ⟨hal-01819945⟩

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