Section 3 - Template 90 : Space view perspective or orthographic
Templates for Section 3
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| Octets | Key | Type | Content |
| 15 | shapeOfTheEarth | codetable | Shape of the earth (see Code Table 3.2) |
| 16 | scaleFactorOfRadiusOfSphericalEarth | unsigned | Scale factor of radius of spherical earth |
| 17-20 | scaledValueOfRadiusOfSphericalEarth | unsigned | Scaled value of radius of spherical earth |
| 21 | scaleFactorOfMajorAxisOfOblateSpheroidEarth | unsigned | Scale factor of major axis of oblate spheroid earth |
| 22-25 | scaledValueOfMajorAxisOfOblateSpheroidEarth | unsigned | Scaled value of major axis of oblate spheroid earth |
| 26 | scaleFactorOfMinorAxisOfOblateSpheroidEarth | unsigned | Scale factor of minor axis of oblate spheroid earth |
| 27-30 | scaledValueOfMinorAxisOfOblateSpheroidEarth | unsigned | Scaled value of minor axis of oblate spheroid earth |
| 31-34 | Nx | unsigned | Nx - number of points along X-axis (columns) |
| 35-38 | Ny | unsigned | Ny - number of points along Y-axis (rows or lines) |
| 39-42 | latitudeOfSubSatellitePoint | signed | Lap - latitude of sub-satellite point |
| 43-46 | longitudeOfSubSatellitePoint | signed | Lop - longitude of sub-satellite point |
| 47 | resolutionAndComponentFlags | codeflag | Resolution and component flags (see Flag Table 3.3) |
| 48-51 | dx | unsigned | dx - apparent diameter of Earth in grid lengths, in X-direction |
| 52-55 | dy | unsigned | dy - apparent diameter of Earth in grid lengths, in Y-direction |
| 56-59 | Xp | unsigned | Xp - X-coordinate of sub-satellite point (in units of 10-3 grid length expressed as an integer) |
| 60-63 | Yp | unsigned | Yp - Y-coordinate of sub-satellite point (in units of 10-3 grid length expressed as an integer) |
| 64 | scanningMode | codeflag | Scanning mode (flags - see Flag Table 3.4) |
| 65-68 | orientationOfTheGrid | signed | Orientation of the grid; i.e., the angle between the increasing Y-axis and the meridian of the sub-satellite point in the direction of increasing latitude (see Note 3) |
| 69-72 | Nr | unsigned | Nr - altitude of the camera from the Earth's centre, measured in units of the Earth's (equatorial) radius multiplied by a scale factor of 106 (see Notes 4 and 5) |
| 73-76 | Xo | unsigned | Xo - X-coordinate of origin of sector image |
| 77-80 | Yo | unsigned | Yo - Y-coordinate of origin of sector image |
( 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 69-72 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 180oE if the sub-satellite point is the North Pole; or the meridian 0o if the sub-satellite point is the South Pole.
( 4) The apparent angular size of the Earth will be given by 2 * Arcsin (106 )/Nr).
( 5) For orthographic view from infinite distance, the value of Nr should be encoded as missing (all bits set to 1).
( 6) The horizontal and vertical angular resolutions of the sensor (Rx and Ry), needed for navigation equation, can be calculated from the following: Rx = 2 * Arcsin (106 )/Nr)/ dx Ry = 2 * Arcsin (106 )/Nr)/ dy
( 7) A scaled value of radius of spherical Earth, or major or minor axis of oblate spheroid Earth is derived from applying appropriate scale factor to the value expressed in metres.
( 8) General reference information pertaining to the projections used for satellite data can be found in Section 4.4 of "LRIT/HRIT Global Specification", Doc. No. CGMS 03, Issue 2.6, Date 12 August 1999 (http://www.eumetsat.int/Home/Main/AboutEUMETSAT/InternationalRelations/CGMS/groups/cps/documents/document/pdf_cgms_03.pdf, page 20 onwards)