Dr. Stefan Wunderle Profile

Dr. Stefan Wunderle

at Univ Bern

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Publications (7)

Proceedings Article | 17 October 2019 Paper

Cloud detection and visibility estimation during night time using thermal camera images

Céline Portenier, Beat Ott, Peter Wellig, Stefan Wunderle

Proceedings Volume 11158, 1115805 (2019) https://doi.org/10.1117/12.2533237

KEYWORDS: Clouds, Target detection, Visibility, Cameras, Visibility through fog, Thermography, Edge detection, Infrared radiation

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Reduced visibility and adverse cloud cover is a major issue for aviation, road traffic, and military activities. Synoptic meteorological stations and LIDAR measurements are common tools to detect meteorological conditions. However, a low density of meteorological stations and LIDAR measurements may limit a detailed spatial analysis. While geostationary satellite data is a valuable source of information for analyzing the spatio-temporal variability of fog and clouds on a global scale, considerable effort is still required to improve the detection of atmospheric variables on a local scale, especially during the night.

In this study we propose to use thermal camera images to (1) improve cloud detection and (2) to study visibility conditions during nighttime. For this purpose, we leverage FLIR A320 and FLIR A655sc Stationary Thermal Imagers installed in the city of Bern, Switzerland. We find that the proposed data provides detailed information about low clouds and the cloud base height that is usually not seen by satellites. However, clouds with a small optical depth such as thin cirrus clouds are difficult to detect as the noise level of the captured thermal images is high.

The second part of this study focuses on the detection of structural features. Predefined targets such as roof windows, an antenna, or a small church tower are selected at distances of 140m to 1210m from the camera. We distinguish between active targets (heated targets or targets with insufficient thermal insulation) and passive structural features to analyze the sensor's visibility range. We have found that a successful detection of some passive structural features highly depends on incident solar radiation. Therefore, the detection of such features is often hindered during the night. On the other hand, active targets can be detected without difficulty during the night due to major differences in temperature between the heated target and its surrounding non-heated objects. We retrieve response values by the cross-correlation of master edge signatures of the targets and the actual edge-detected thermal camera image. These response values are a precise indicator of the atmospheric conditions and allows us to detect restricted visibility conditions.

Proceedings Article | 5 October 2017 Paper

Automatic visibility retrieval from thermal camera images

Céline Dizerens, Beat Ott, Peter Wellig, Stefan Wunderle

Proceedings Volume 10432, 104320L (2017) https://doi.org/10.1117/12.2278652

KEYWORDS: Visibility, Cameras, Forward looking infrared, Thermography, Infrared cameras, Target detection, Edge detection, Panoramic photography, Infrared imaging, Infrared radiation

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SPIE Journal Paper | 7 July 2015

Hyperspectral imaging spectroscopy: a promising method for the biogeochemical analysis of lake sediments

Christoph Butz, Martin Grosjean, Daniela Fischer, Stefan Wunderle, Wojciech Tylmann, Bert Rein

JARS, Vol. 9, Issue 01, 096031, (July 2015) https://doi.org/10.1117/12.10.1117/1.JRS.9.096031

KEYWORDS: Calibration, Hyperspectral imaging, Chemical analysis, Spectroscopy, Absorption, Imaging spectroscopy, Data modeling, RGB color model, Signal to noise ratio, Cameras

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Proceedings Article | 24 February 2004 Paper

Operational estimation of vegetation index (NDVI), vegetation cover, and leaf area index using NOAA-AVHRR data in an alpine environment

Stefan Wunderle, David Oesch, Adrian Hauser, Nando Foppa

Proceedings Volume 5232, (2004) https://doi.org/10.1117/12.511020

KEYWORDS: Vegetation, Data archive systems, Aerosols, Sensors, Satellites, Atmospheric corrections, Snow cover, Reflectivity, Remote sensing, Aluminium phosphide

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Proceedings Article | 24 February 2004 Paper

Operational application of NOAA–AVHRR data for mapping lake surface temperatures in an alpine environment: feasibilty and validation

David Oesch, Adrian Hauser, Stefan Wunderle

Proceedings Volume 5232, (2004) https://doi.org/10.1117/12.511091

KEYWORDS: Satellites, Temperature metrology, Clouds, Meteorology, Satellite imaging, Image processing, Associative arrays, Sensors, Algorithm development, Earth observing sensors

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Proceedings Article | 16 February 2004 Paper

Retrieval of aerosol optical depth (AOD) using NOAA AVHRR data in an alpine environment

Adrian Hauser, David Oesch, Stefan Wunderle

Proceedings Volume 5235, (2004) https://doi.org/10.1117/12.511045

KEYWORDS: Reflectivity, Aerosols, Satellites, Atmospheric optics, Atmospheric particles, Clouds, Bidirectional reflectance transmission function, Ocean optics, Data modeling, Atmospheric modeling

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Proceedings Article | 14 March 2003 Paper

Operational snow cover estimation at subpixel scale using NOAA-AVHRR data

Nando Foppa, Stefan Wunderle, Adrian Hauser

Proceedings Volume 4886, (2003) https://doi.org/10.1117/12.474409

KEYWORDS: Snow cover, Reflectivity, Sensors, Clouds, Satellites, Remote sensing, Modeling, Geography, Climatology, Satellite imaging

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Showing 5 of 7 publications

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