Sun reflex

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Sun reflection observed by the ISS in the Okavango Delta

A sun reflex ( English Sunglint ), also the sun glint , sun shine or sun reflection is an optical phenomenon that is visible to an observer, when sunlight is reflected on a water surface in the same angle as the angle of observation. This phenomenon is particularly in the area of Satellite - Remote Sensing of importance, where the effect of such. B. can occur when satellite images of ocean surfaces are created. For a human observer on the ground, solar reflections are e.g. B. the typical glitter of a lake.

Disturbing influence

The occurrence of reflections from the sun is often seen as a source of interference in remote sensing, since the glaring water surfaces can overlay interesting image areas. Especially in oceanography , where satellite data z. If, for example, they are used to determine chlorophyll concentrations in ocean and coastal regions, solar reflections can have a considerable influence on the accuracy and quality of the information. Methods for alleviating this negative influence are the subject of numerous studies.

alternative description
An oil slick in the Gulf of Mexico , visible as bright streaks (image section).

Positive benefit

Despite the largely negative influence, the effect opens up some unique possibilities in certain constellations and applications. The detection of naturally occurring as well as man-made oil spills is simplified, as these soften the wave formation on the surface of the water, whereby the incident sunlight is reflected less diffusely than by the surrounding water surfaces. Depending on the viewing angle, the oil slick appears lighter or darker than the surrounding water.

When the sun shines, certain atmospheric effects may become visible that otherwise could not be recorded. For example, in a satellite image of the Arabian Sea, atmospheric gravity waves are visible, as the air masses, which are sinking due to gravity , hit the surface of the water, which roughen the surface of the water and thus scatters the incident sunlight more diffusely.

Web links

Commons : Solar reflections observed on earth  - collection of images, videos and audio files
Commons : Solar reflections observed from space  - collection of images, videos and audio files

Individual evidence

  1. ↑ Susan Kay, John D. Hedley & Samantha Lavender: Sun Glint Correction of High and Low Spatial Resolution Images of Aquatic Scenes: a Review of Methods for Visible and Near-Infrared Wavelengths. In: Remote Sensing - Open Access Journal Volume 1–4, 2009, pp. 697–730, doi: 10.3390 / rs1040697 .
  2. ↑ Maria Adamo, Giacomo De Carolis, Vito De Pasquale & Guido Pasquariello: Detection and tracking of oil slicks on sun-glittered visible and near infrared satellite imagery. In: The International Journal of Remote Sensing. Volume 30-24, 2009, pp. 6403-6427, doi: 10.1080 / 01431160902865772 .
  3. ↑ NASA image of the day from May 26 , 2005 , accessed on May 6, 2019