Section 7 - Template 3 : Grid point data - complex packing and spatial differencing Note: For most templates, details of the packing process are described in regulation 92.9.4
Templates for Section 7
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| Octets | Key | Type | Content |
| 6-ww | First value(s) of original (undifferenced) scaled data values, followed by the overall minimum of the differences. The number of values stored is 1 greater than the order of differentiation, and the field width is described at octet 49 of Data Representation Template 5.3. (see Note 1) | ||
| [ww+1]-xx | NG group reference values (X1 in the decoding formula), each of which is encoded using the number of bits specified in octet 20 of Data Representation Template 5.0. Bits set to zero shall be appended where necessary to ensure this sequence of numbers ends on an octet boundary. | ||
| [xx+1]-nn | Same as for Data Representation Template 7.2. |
( 1) Referring to the notation in Note (1) of Data Representation Template 5.3, at order 1, the values stored in octets 6-ww are g1 and gmin. At order 2, the values stored are h1, h2, and hmin.
( 2) Extra descriptors related to spatial differencing are added before the splitting descriptors, to reflect the separation between the 2 approaches. It enables to share software parts between cases with and without spatial differencing.
( 3) The position of overall minimum after initial data values is a choice that enables less software management.
( 4) Overall minimum will be negative in most cases. First bit should indicate the sign: 0 if positive, 1 if negative.