Measurements and modeling of the vertical radiance profile of sea and sky backgrounds using infrared sensors

Rheenen, Arthur D. van; Brendhagen, Erik; Heen, Lars Trygve

doi:10.1117/12.800187

Cited by 2 publications

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As the ships move away from the observer the hull "moves up" in the image, closer to the horizon. In sea and sky background studies [2] we observed that the radiance from the sea increases towards the horizon reducing the contrast with distance. Calculated decay rates are quite sensitive to this change in contrast.…”

Section: Discussionmentioning

confidence: 91%

Comparison of distance dependence of ship signature and intensity of ship exhaust gas measured in both MWIR and LWIR transmission bands

2009

Self Cite

View full text Add to dashboard Cite

A ship's exhaust gas contains both hot gas molecules, which emit infrared radiation at specific wavelengths (line emitters), and soot particles which emit broad-banded, like a black body. Our modeling shows that the observed radiance from these emissions falls at different rates with distance. The attenuation of intensity is caused by absorption and scattering of the emitted radiation in the atmosphere. The hottest part of the exhaust plume is spatially confined to a relative small volume. Usually, a ship's hull and its superstructure have a higher temperature than the sky or sea background. The temperature difference is generally not very large. However, the ship has a spatial extent that is much larger than the plume's. In this work we study how both the emitted radiation from the plume and the ship's total signature decrease with increasing distance. This study is based on experimental data that was collected during a measurement campaign at the southwest coast of Norway. Shore-based digital IR cameras, both LWIR and MWIR, recorded image sequences of ships as they sailed away from close to shore (~ 1 km) in a zigzag pattern out to about 10 km. We used a statistical method to identify the gas cloud pixels and used their integrated radiance as a measure for the plume intensity. The ship signature is defined here as the integrated radiance over all the ship's pixels in the imagery. From infrared spectroscopic data, collected using a Fourier Transform Infrared spectrometer aimed at the ship's plume when the ship is close to shore, a model is obtained for the composition of the exhaust gas. This model was used to perform FASCODE simulations to study numerically the attenuation with distance of the plume radiance. Our work shows that this approach may be well suited to explain the observed signal decay rate with distance.

show abstract

Section: Discussionmentioning

confidence: 91%

Comparison of distance dependence of ship signature and intensity of ship exhaust gas measured in both MWIR and LWIR transmission bands

2009

Self Cite

View full text Add to dashboard Cite

show abstract

“…In the last decade, a number of experiments has been set-up to collect data with electro-optical sensors in a variety of locations and conditions. TNO was involved in experiments in the Mediterranean Sea near Crete (1996, [1]) and Nettuno (1998, [2]), the Baltic Sea (1999, [3]), the Carribean (1999, [4]), the North Sea (2000, [5]), and Chesapeake Bay (2006, [6]). As a result a comprehensive data base has been obtained, which allows the validation of contrast and clutter models [7], the prediction of range performance for given sensor parameters [8] and the development of detection and tracking algorithms [9,10,11].…”

Section: Introductionmentioning

confidence: 99%

Optical characteristics of small surface targets, measured in the False Bay, South Africa; June 2007

et al. 2009

View full text Add to dashboard Cite

During the False Bay trial (June 2007), the performance of a set of three optical sensors was tested against several small surface targets in a coastal area: a hyperspectral camera, a camera with a rotating polarization filter and a high resolution camera. One objective was the validation of a contrast and clutter model for the visual spectral band in this type of scenarios. Another issue was to test the benefit of using a polarisation filter and a hyperspectral unit in front of standard TV cameras. Finally the loss in identification capability of a high resolution camera at long range due to atmospheric blur was investigated. Data were collected of targets in near-sun direction at ranges up to seven kilometers, in all cases for down looking angles (targets below the horizon). Environmental parameters such as solar irradiance and windspeed were measured as input for the contrast and clutter models. Spatial, spectral and temporal effects of the target contrast and of the background clutter behaviour in the visual spectral band were determined as function of range and compared with model predictions. Samples of data and predictions are presented in this paper. The spatial and temporal target characteristics are of key importance for the development of algorithms for target detection, classification and tracking. Finally, rules of thumb, based on the measurements and model predictions, on the detection and identification range performances of specific optical sensors against small surface targets in a maritime environment are presented.

show abstract

Measurements and modeling of the vertical radiance profile of sea and sky backgrounds using infrared sensors

Cited by 2 publications

References 0 publications

Comparison of distance dependence of ship signature and intensity of ship exhaust gas measured in both MWIR and LWIR transmission bands

Comparison of distance dependence of ship signature and intensity of ship exhaust gas measured in both MWIR and LWIR transmission bands

Optical characteristics of small surface targets, measured in the False Bay, South Africa; June 2007

Contact Info

Product

Resources

About