4

I'm confused about the use of this quantity. For example eumetsat

on pag. 16 radiance is equal to:

Physical Units = Cal_Offset + (Cal_Slope x Level 1.5 Pixel Count)

expressed in mWm-2 sr-1 (cm-1)-1

and table in page 20 represents dynamic range in W/m^2*sr*um unit.

The question is: when I read seviri spectral channel from MSG2/3 and after the transformation above, do I have values expressed in first or second units?

1

They are not using uniform units. The first is using mW (miliwatts) for power and cm (centimeters) for wavelength, and the latter W (watts) for power and um (micrometers) for wavelength.

You can convert between the two using the conversion factors for both: 1 mW = 10^-3 W and 1 um = 10^-6 m.

According to the documentation, in 3.1.7, I would guess that the representation uses the first convention you mention. You could use the theoretical properties of a known target/surface/material to confirm.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.