Why do parts of my image appear to have sun glare?

Sun glare (or more usually "sun glint") is caused by one or more features on the surface reflecting the sun in a mirror-like way that saturates the sensor, and this can compromise the quality of your imagery.


If you are planning to order visible imagery, you should be aware of sun glint. Sun glint is caused by features in an image being oriented like mirrors in such a way as to create spikes in the sun's energy. It is the same as when you look at the sea from certain angles during sunny conditions and at a certain distance in the direction of the sun, the sea can appear very bright. In certain circumstances, sun glint is a useful phenomenon as it contains information about the surface (for example see here), but in many circumstances it is a problem because it can cause saturation of the sensor and can mask features on the surface that the customer is interested in looking at (for example see here). Furthermore, it does not just affect  water, it can affect certain types of hard surface too, notably roofs and other smooth surfaces and objects.


Unfortunately, avoiding sun glint is difficult. It involves taking into account the imaging angle, the sun angle at the time of imaging, and the target angles (feature of interest on the surface). Over water, there has been some success in using the near infrared channel to compensate for sun glint and using radiative transfer modelling, but these all require expertise that many of our customers do not have.

If you are concerned about sun glint, please contact us to discuss the level of risk. It very much depends on the type of feature you are imaging (water and hard, flat and smooth surfaces are most at risk) and whether the sun is very high or low (more risk at higher angles for imaging from high altitudes). Unfortunately, we cannot guarantee that there will be no sun glint in your image, and in general it is too complex to calculate whether sun glint will be present for a particular type of feature, although we are happy to provide proposed imaging parameters though if you feel comfortable exploring this yourself.