North and South Island Yard Grids (NIYG, SIYG)

The North and South Island Yard Grids (NIYG; SIYD) are the NZGD1949 projections that were used for the 1:63,360 (inch-to-the-mile) NZMS1 topographic mapping from 1942.

These projections were superseded by the NZMG, although some older databases still hold data in terms of them.

The key parameters of the NIYG are summarised below:

Name:	North Island Yard Grid
Abbreviation:	NIYG
Projection type:	Transverse Mercator
Reference ellipsoid:	International 1924
Datum:	NZGD1949
Origin latitude:	39° 06' 00" South
Origin longitude:	175° 30' 00" East
False Northing:	400,000 yards North
False Easting:	300,000 yards East
Central meridian scale factor:	1.0000

The key parameters of the SIYG are summarised below:

Name:	South Island Yard Grid
Abbreviation:	SIYG
Projection type:	Transverse Mercator
Reference ellipsoid:	International 1924
Datum:	NZGD1949
Origin latitude:	44° 06' 00" South
Origin longitude:	171° 30' 00" East
False Northing:	500,000 yards North
False Easting:	500,000 yards East
Central meridian scale factor:	1.0000