Section 3 - Template 100 : Triangular grid based on an icosahedron (see Attachment I.2-GRIB-Att.)
Templates for Section 3
More Sections
| Octets | Key | Type | Content |
| 15 | n2 | unsigned | n2 - exponent of 2 for the number of intervals on main triangle sides |
| 16 | n3 | unsigned | n3 - exponent of 3 for the number of intervals on main triangle sides |
| 17-18 | Ni | unsigned | ni - number of intervals on main triangle sides of the icosahedron |
| 19 | nd | unsigned | nd - Number of diamonds |
| 20-23 | latitudeOfThePolePoint | signed | Latitude of the pole point of the icosahedron on the sphere |
| 24-27 | longitudeOfThePolePoint | unsigned | Longitude of the pole point of the icosahedron on the sphere |
| 28-31 | longitudeOfFirstDiamondCenterLine | unsigned | Longitude of the center line of the first diamond of the icosahedron on the sphere |
| 32 | gridPointPosition | codetable | Grid point position (see Code table 3.8) |
| 33 | numberingOrderOfDiamonds | codeflag | Numbering order of diamonds (flag - see Flag table 3.9) |
| 34 | scanningModeForOneDiamond | codeflag | Scanning mode for one diamond (flags - see Flag table 3.10) |
| 35-38 | totalNumberOfGridPoints | unsigned | nt - total number of grid points |
( 1) For more details see Attachment I.2-GRIB-Att to the Manual of Codes, Vol. I, Part B- definition of a triangular grid based on an icosahedron
( 2) The origin of the grid is an icosahedron with 20 triangles and 12 vertices. The triangles are combined to nd quadrangles, the so-called diamonds (e.g. if nd = 10, two of the icosahedron triangles form a diamond, and if nd = 5, 4 icosahedron triangles form a diamond). There are two resolution values called n2 and n3 describing the division of each triangle side. Each triangle side is divided into ni equal parts where ni = 3**n3 * 2**n2 with n3 either equal to 0 or to 1. In the example of Attachment I.2-GRIB-Att, the numbering order of the rectangles is anti-clockwise with a view from the pole point on both hemispheres. Diamonds 1 to 5 are northern hemisphere and diamonds 6 to 10 are Southern Hemisphere.
( 3) The exponent of 3 for the number of divisions of triangle sides is used only with a value of either 0 or 1.
( 4) The total number of grid points for one global field depends on the grid point position. If e.g. the grid points are located at the vertices of the triangles nt = (ni + 1) * (ni + 1) * nd since grid points at diamond edges are contained in both adjacent diamonds and for the same reason the pole points are contained in each of the five adjacent diamonds.