Visualization of all-sky polarization images referenced in the instrument, scattering, and solar principal planes

Eshelman, Laura M.; Shaw, Joseph A.

doi:10.1117/1.oe.58.8.082418

Cited by 14 publications

(7 citation statements)

References 47 publications

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“…imag (•) and real (•) denote the imaginary and real parts of the complex number respectively. To obtain the AOP information under the observation meridian coordinate system, the conversion is required [31]:…”

Section: Heading Measurement Based On the Improved Berry Modelmentioning

confidence: 99%

Robust Heading Measurement Based on Improved Berry Model for Bionic Polarization Navigation

Zhang

Wang

et al. 2023

IEEE Trans. Instrum. Meas.

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With the advantages of anti-interference and no accumulated error, bionic polarization heading measurement has important military significance and research value for autonomous navigation. However, the heading robustness is seriously affected by the accuracy of skylight polarization model and the existing methods all use the Rayleigh scattering model without considering the atmospheric depolarization. Therefore, this paper proposed an innovative method of polarization heading measurement based on Berry model to considering the influence of depolarization neutral points. And this model is improved by controlling the neutral points with correction coefficients to realize high-robustness heading measurement. On this basis, the improved Berry model is further used to calibrate the sensor parameters outdoors, which separates the skylight polarization model error from the sensor error without expensive instruments and complicated processes, and improves the heading measurement accuracy. In the experiments with changing solar altitude, the average of heading error STD after field calibration is 20.86% lower than that of Berry model and 92.85% lower than that of Rayleigh model, which shows great advancement in actual measurements.

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Section: Heading Measurement Based On the Improved Berry Modelmentioning

confidence: 99%

Robust Heading Measurement Based on Improved Berry Model for Bionic Polarization Navigation

Zhang

Wang

et al. 2023

IEEE Trans. Instrum. Meas.

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“…A Stokes vector is defined with respect to a plane of reference. Often, the scattering plane, which contains both the incoming solar illumination vector and the view vector, is used as a reference plane (e.g., Eshelman and Shaw, 2019). This has the advantage that U ≈ 0 within the scattering plane and Q contains all information about the polarized signal.…”

Section: Specmacs Polarization Cameras and Data Processingmentioning

confidence: 99%

“…The z axis points in the direction of the optical axis of the camera. For further analysis, each measured Stokes vector is rotated into its scattering plane which is unique for each pixel (Hansen and Travis, 1974;Eshelman and Shaw, 2019), and we only evaluate Q. The window in front of the polarization cameras affects the polarization state of the measurements.…”

Section: Specmacs Polarization Cameras and Data Processingmentioning

confidence: 99%

High-spatial-resolution retrieval of cloud droplet size distribution from polarized observations of the cloudbow

Pörtge¹,

Kölling

Weber³

et al. 2023

Atmos. Meas. Tech.

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Abstract. The cloud droplet size distribution is often described by a gamma distribution defined by the effective radius and the effective variance. The effective radius is directly related to the cloud's optical thickness, which influences the radiative properties of a cloud. The effective variance affects, among other things, the evolution of precipitation. Both parameters can be retrieved from measurements of the cloudbow. The cloudbow (or rainbow) is an optical phenomenon that forms due to the single scattering of radiation by liquid cloud droplets at the cloud edge. The polarized radiance of the cloudbow crucially depends on the cloud droplet size distribution. The effective radius and the effective variance can be retrieved by fitting model simulations (stored in a lookup table) to polarized cloudbow observations. This study uses measurements from the wide-field polarization-sensitive camera of the spectrometer of the Munich Aerosol Cloud Scanner (specMACS) aboard the German “High Altitude and LOng range research aircraft” (HALO). Along with precise cloud geometry data derived by a stereographic method, a geolocalization of the observed clouds is possible. Observations of the same cloud from consecutive images are combined into one radiance measurement from multiple angles. Two case studies of trade-wind cumulus clouds measured during the EUREC4A (ElUcidating the RolE of Cloud-Circulation Coupling in ClimAte) field campaign are presented, and the cloudbow technique is demonstrated. The results are combined into maps of the effective radius and the effective variance with a 100 m × 100 m spatial resolution and large coverage (across-track swath width of 8 km). The first case study shows a stratiform cloud deck with distinct patches of large effective radii up to 40 µm and a median effective variance of 0.11. specMACS measures at a very high angular resolution (binned to 0.3∘) which is necessary when large droplets are present. The second case study consists of small cumulus clouds (diameters of approximately 2 km). The retrieved effective radius is 7.0 µm, and the effective variance is 0.08 (both median values). This study demonstrates that specMACS is able to determine the droplet size distribution of liquid water clouds even for small cumulus clouds, which are a problem for traditional droplet size retrievals based on total reflectances.

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“…The geomagnetic field also changes in such a journey and migratory birds reach regions where the intensity of the field is lower than in their breeding grounds and possibly falls outside of the functional window of the magnetic compass (Wiltschko, 1978). However, birds are able to adapt to previously unexperienced intensities of the magnetic field during migration, according to laboratory and virtual displacement experiments (Fransson et al, 2001;Wiltschko et al, 2006;Winklhofer et al, 2013;Bulte et al, 2017). Another problem is that the magnetic compass cannot be used near the magnetic equator where the inclination is close to 0° (Wiltschko and Wiltschko, 1972;Wiltschko, 1974;Schwarze et al, 2016).…”

Section: ) Magnetic Cues Calibrate Celestial Compassesmentioning

confidence: 99%

A hierarchy of compass systems in migratory birds

Pakhomov

Chernetsov

2020

BioComm

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Migratory birds use several different sources of orientation information. They have at least three compass systems based on different cues: the sun and polarized light, the stars and their constellations, and the geomagnetic field. The concurrent information obtained from these three compasses is redundant, therefore the compasses need to have a hierarchy and must be calibrated relative to each other. One of the compasses should dominate the others, or some orientation cue should be used to calibrate the remaining compass systems. Results of experiments on a variety of songbird species demonstrate that while astronomical cues calibrate the magnetic compass during the pre-migratory period, strategies used during the migratory period are more diverse. In the present review, we analyze the results of all crucial cue-conflict studies, mostly performed in nocturnal songbird migrants; we also try to understand why some migratory species calibrate their magnetic compass on sunset cues while others use the geomagnetic field or stars as a primary cue source, and we examine why the previous hypothesis could not explain the findings of all cue-conflict experiments.

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Visualization of all-sky polarization images referenced in the instrument, scattering, and solar principal planes

Cited by 14 publications

References 47 publications

Robust Heading Measurement Based on Improved Berry Model for Bionic Polarization Navigation

Robust Heading Measurement Based on Improved Berry Model for Bionic Polarization Navigation

High-spatial-resolution retrieval of cloud droplet size distribution from polarized observations of the cloudbow

A hierarchy of compass systems in migratory birds

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