sarproz-group

Orbit heading

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    • #4969
      antig
      Participant

      Hi
      I have confusion to detect orbit azimuth value. Azimuth is clockwise angle respect from the North
      So in SARPROZ SiteDescription.txt I have AcqHeading values. In my mind heading and azimuth should be same values
      But values are
      DESC_Heading AcqHeading=-9.3537 deg
      ASC_heading AcqHeading=-167.9874 deg

      1) What those direction values discribe?
      2) respect which axe? (East or North)?
      3) What is the wise of angle (clock or counter clockwise)?

      From ESA SNAP forum I found post, where azimuth of orbit is close to right (snap.png). (diffrent AOI’s). To compeare numbers looks like In SARPROZ has ASC and DESC headings (in my mind orbital direction) values exchanged.

      I can not found connection between SARPOZ heading value and SNAP correct value

      Thanks for answer

    • #4971
      periz
      Keymaster

      Hi Antig,
      sun-synchronous near-polar orbits are almost parallel to the north-south direction. However, both when going up (ascending) and down (descending) the satellite path is slightly squinted to the west (as the earth rotates). if you draw this on a paper, and if you take the south direction as reference, u will see those angles (that you mention) as positive counterclockwise. yes, it might sound weird (to take south and counter clock wise as reference), but this was inherited by sarproz from the environment where it grew up. please note that this is anyway at least related to the north-south direction, while what you find in snap is related to some other direction: https://www.sarproz.com/groups/sarproz-group/forum/topic/is-heading-angle-in-sitedescription-txt-file-ve-w-r-t-to-geographic-north/
      best

    • #4973
      antig
      Participant

      Thank You Daniele
      I understood it now
      Agree, that this is weird, but possible, way to illustrate direction.

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