Grid definition - Space view perspective or orthographic

      Octet
      No.
      Contents
      7-8Nx - number of points along X-axis
      9-10Ny - number of points along Y-axis
      11-13Lap - latitude of sub-satellite point
      14-16Lop - longitude of sub-satellite point
      17Resolution and component flags (see Code table 7)
      18-20dx - apparent diameter of Earth in grid lengths, in X-direction
      21-23dy - apparent diameter of Earth in grid lengths, in Y-direction
      24-25Xp - X-coordinate of sub-satellite point
      26-27Yp - Y-coordinate of sub-satellite point
      28Scanning mode (flags - see Code table 8)
      29-31Orientation of the grid; i.e. the angle in millidegrees between the increasing Y-axis and the meridian of the sub-satellite point in the direction of increasing latitude (see Note 3)
      32-34Nr - altitude of the camera from the Earth's center, measured in units of the Earth's (equatorial) radius (see Note 4)
      35-36Xo - X-coordinate of origin of sector image
      37-38Yo - Y-coordinate of origin of sector image
      39-44Set to zero (reserved)



      NOTES:

      1. It is assumed that the satellite is at its nominal position, i.e. it is looking directly at its sub-satellite point.

      2. Octets 32-34 shall be set to all ones (missing) to indicate the orthographic view (from infinite distance).

      3. It is the angle between the increasing Y-axis and the meridian 180°E if the sub-satellite point is the North Pole; or the meridian 0° if the sub-satellite point is the South Pole.

      4. The apparent angular size of the Earth will be given by 2 x Arcsin (1 / Nr).

      5. The horizontal and vertical angular resolutions of the sensor (Rx and Ry), needed for navigation equations, can be calculated from the following:
        Rx = 2 x Arcsin (1 / Nr) / dx
        Ry = 2 x Arcsin (1 / Nr) / dy



      Back to Top