Inconsistency in location of parameters used by OpticalCalibration?

Hi all,


I try to do a TOA optical calibration on a PHR image with otbcli_OpticalCalibration.
The application displays parameters used from DIMAP file. It seems that values used for Sun angles and Viewing angles are not taken is the same location in the image.
Sun angles are taken at Top Center of image.
Viewing angles are taken at Center of image.

Configuration setup

My system: CentOS 7.6
Version of the OTB: 7.1
I installed the OTB with: the binaries

Description of my issue

$ otbcli_OpticalCalibration -in IMG_PHR1A_MS_201805151114528_SEN_3122825101-004_R1C1.JP2 -out toto.tif -level toa

2020-11-05 12:30:51 (INFO): Loading kwl metadata from official product in file IMG_PHR1A_MS_201805151114528_SEN_3122825101-004_R1C1.JP2
2020-11-05 12:30:51 (INFO) OpticalCalibration:
File: IMG_PHR1A_MS_201805151114528_SEN_3122825101-004_R1C1.JP2
Sensor detected: PHR 1A
Parameters extract from input image:
        Acquisition Sun Elevation Angle: 59.095
        Acquisition Viewing Elevation Angle: 73.6414


$ grep LOCATION_TYPE -A 15 DIM_PHR1A_MS_201805151114528_SEN_3122825101-004.XML | egrep “LOCATION|SUN_ELEVATION|<INCIDENCE_ANGLE>”

      <SUN_ELEVATION unit="deg">59.09496590146077</SUN_ELEVATION>
      <SUN_ELEVATION unit="deg">59.17540823032729</SUN_ELEVATION>
      <SUN_ELEVATION unit="deg">59.25575383043164</SUN_ELEVATION>

As we can see Sun Angles are taken at the Top Center Location whereas the Viewing angle are taken at the Center Location (90 - 73.6414 = 16.3586).

Why Sun and Viewing angle values are not taken at the same location ?

Thanks for your answers.