# view zenith angle and view azimuth angle with Quickbird

I am trying to do an atmospheric correction on a Quickbird scene. I am creating a user-defined geometry which requires six parameters. The six parameters are solar zenith angle, solar azimuth angle, view zenith angle, view azimuth angle, month, and day. The Quickbird metadata file gives a "mean elevation angle of the sun from horizontal" so I think I am correct in assuming that

``````mean solar zenith angle = 90 - meanSunEl
``````

and that

``````mean solar azimuth angle = meanSunAz
``````

I am unclear about how to determine the view zenith angle and view azimuth angle. The Quickbird documentation gives meanSatEl as the "mean elevation angle of the satellite with respect to the center line, in degrees." I am unsure what is meant by "respect to the center line." Zenith? Would it simply be

``````mean view zenith angle = 90 - meanSatEl ?
``````

I also am unsure whether view azimuth angle is equivalent to meanSatAz, which is defined as "mean azimuth angle of the satellite with respect to the center line, in degrees." The metadata also has values for InTrackViewAngle, CrossTrackViewAngle, and offNadirViewAngle.

First, there is problably a typo in your question, but here are the sun angles

``````solar zenith angle = 90 - meanSunEl

solar azimuth angle = meanSunAz
``````

this is also valid for the mean satellite angles

``````MEAN satellite zenith angle = 90 - meanSatEl

MEAN satellite azimuth angle = meanSatAz
``````

That being said, it is important to realize that you can consider the sun angles to be identical everywhere on the image only because the sun is very far and the time needed for one acquisition is small. However, this is not true for the image angles: the satellite is not that high (initially 450 km), therefore the satellite angles change depending on your position on the image. If you need high precision everywhere on the scene (away from the center line), then you need to look at how the satellite is tilted during acquisition. This is what you get with InTrackViewAngle, CrossTrackViewAngle (relative to the track, which has its own azimuth), and offNadirViewAngle (relative to the Nadir, aka the perpendicular projection of the satellite on the ground)

• Thanks. Hopefully I fixed the typos. I appreciate the quick response. I will try and learn more about the track view angles. – user14241 Mar 13 '15 at 14:43

if SUN_AZIMUTH = 153 then sensor_zimuth would be=153 and if sun zenith is = 57, then sensor zenith also equal to =57