# S2 geometry definition

Hi everyone,

I am trying to understand the definition of the sun and view geometry in S2. My interest is in finding the correct direction to detect cloud shadows analytically.

As you can see in this example, the direction of illumination is quite clear by visual inspection (line). Neglecting the small distortion of the UTM projection, I can assume that North is directed towards the top of the scene. From X,Y values of the two pin positions I can calculate the apparent sun azimuth angle, which is 172.6°. The sun azimuth angle in the product is given as 164.5°. I know that there has to be a difference between the sun azimuth in the product and the apparent sun azimuth visible by clouds and their shadows. As clouds are elevated they are not shown at their actual position above ground, if the observation is not in nadir view (view zenith!=0).

For S3-OLCI I successfully derived a correction of the sun azimuth angle, but if I try to use it with S2, the approach fails. So I would like to know: Is there a difference in the definition of the angles between S2 and S3?

Kind regards,
Dagmar