Grid 1: Mercator
Grids
| Octets | Key | Type | Content |
| 7-8 | Ni | signed | Ni number of points along a parallel |
| 9-10 | Nj | signed | Nj number of points along a meridian |
| 11-13 | latitudeOfFirstGridPoint | signed | La1 latitude of first grid point |
| 14-16 | longitudeOfFirstGridPoint | signed | Lo1 longitude of first grid point |
| 17 | resolutionAndComponentFlags | codeflag | Resolution and component flags (see Code table 7) |
| 18-20 | latitudeOfLastGridPoint | signed | La2 latitude of last grid point |
| 21-23 | longitudeOfLastGridPoint | signed | Lo2 longitude of last grid point |
| 24-26 | Latin | signed | Latin latitude(s) at which the Mercator projection cylinder intersects the Earth |
| 27 | Set to zero (reserved) | ||
| 28 | scanningMode | codeflag | Scanning mode (flags see Flag/Code table 8) |
| 29-31 | Di | signed | Di longitudinal direction grid length (see Note (2)) |
| 32-34 | Dj | signed | Dj latitudinal direction grid length (see Note (2)) |
| 35-42 | Set to zero (reserved) |
( 1) Latitude and longitude are in millidegrees (thousandths of a degree).
( 2) Grid lengths are in units of metres, at the parallel specified by Latin.
( 3) Latitude values are limited to the range 0-90 000; bit 1 is set to 1 to indicate south latitude.
( 4) Longitude values are limited to the range 0-360 000; bit 1 is set to 1 to indicate west longitude.
( 5) The latitude and longitude of the last grid point from the first grid point should always be given.
( 6) Where items are not given, the appropriate octet(s) should have all bits set to 1, the missing indicator.
( 7) The first and last grid points may not necessarily correspond to the first and last data points, respectively, if the bit-map section is used.