10 March 2009

A story on Land Information New Zealand’s new topographic map series in last month’s Army News raised issues for some Army personnel. Here is some additional information provided by members of the NZDF Geospatial Intelligence Organisation (GIO) who have worked closely with LINZ in the preparation of the new map series.

1. Can I keep using the NZMG Maps within our map libraries?

No. A condition of the replacement programme LINZ is running is that the old NZMG maps have to be returned to LINZ (Land Information New Zealand). From September 2009 only the new NZTopo50 maps will be available from the map library.

2. Is the Waiouru map changing, and if not why not?

The NZMS260 sheet for Waiouru (T20) will no longer be available. You will need sheets BJ34, BJ35, and BJ36 from the new NZTopo50 series. The ATG training area map is a UTM grid/projection product and will not change. That is because it is a ‘train as you fight’ issue as UTM is the grid used on most operations.

3. What do I do with the stock of NZMG maps I have?

As it stands at the moment, they will need to be returned to LINZ. We’re still working through how that will happen.

4. How do I get NZTopo50 maps, who pays for them, and what is the lead time to get them?

The initial supply of NZTopo50 maps, to replace existing stock of NZMS260 maps, is funded by LINZ as a one-off replacement. The NZDF has already provided LINZ with stock numbers of existing NZMS260 maps. The new map series won’t be available for use until it is publicly launched in September 2009. At the moment, the plan is to co-ordinate the changeover via the map library in Trentham. However LINZ may, on JGU instructions, assist by sending the replacements directly to units rather than physically through the library.

5. If I am on exercise or out tramping and need emergency assistance can I only use NZTopo references from September?

You’ll find it harder to get emergency assistance using the old NZMS260 series, as all the emergency services will have switched to the new NZTopo50 series. Call centres will have the ability to convert from old to new but that obviously adds a small delay so it would be better to use only the official National grid.

6. Will Service GPS (PLGR 96+, PLGR II, Garmin) work on the new grid system?

They should. Army was advised of this change two years ago and the only issue identified was with gun laying systems. There is the ‘user definable’ option, in which case the parameters are entered for the new projection and grid (central meridian 173°, scale factor 0.9996 and the false origin in the handout).

The advice from LINZ is that if your GPS does not support NZGD2000, then set it to WGS84, as for all practical purposes, there is no difference between NZGD2000 and WGS84. If your GPS does not support NZTM grid co-ordinates, but it has the facility to allow you to set the parameters for a projection, then the LINZ figures to do that can be provided.

7. Will all the Kit that take location from GPS work on the new Grid ( GLPS, Vector, Ncros, SG12, TAC Nav etc)?

Issues with GLPS (it only takes UTM or NZMG) have been identified. The solution is that the Army/ gunners follow ‘train as you fight’ and use UTM.

8. Will the Grid Magnetic Angle (GMA) I set on the Silva compass change, and if so, why?

No, the magnetic variation will not change. The magnetic variation is the angle between your location and the magnetic North Pole, and your location and the geographic North Pole. Because your location has "moved" 190 m closer to the geographic North Pole, the magnetic variation may change by an extremely tiny amount, so tiny that it won’t have any effect on the magnetic variation that you’ll use with a compass. There will be another cause for a negligible change to the GMA as the new grid and old one aren’t quite parallel i.e. GMA is that angle from grid N to Mag N and grid N moves slightly too. But as you always look at the angle printed on the map to get GMA (as it varies from sheet to sheet but is approx 23° in NZ), users will just take that number. The variation (declination) from north (true) to where the magnetic field points won’t change as that is physical. The GMA will as the old and new grids aren’t parallel. But as you should always take the GMA from the map you are using, this isn’t an issue. The fact that it may be a few degrees different to a previously used one is immaterial. The one the map reader has at the time should be used.

9. Is it correct that latitude and longitude will change?

Yes. The lat/long co-ordinates of a feature on the new NZTopo50 maps will be different to the lat/long co-ordinates of the same feature on the old NZMS260 maps. This is because the datum has changed from NZGD1949 to NZGD2000. The change in datum changed the position of the centre of the earth a small amount, which moves all the latitudes and longitudes a little bit. The difference, for the same latitude and longitude value, is 190 metres to the north, and 10 metres to the east (i.e. in the new NZTopo50 series, a lat/long co-ord will be 190 m north and 10 east of the same lat/long co-ord in the old NZMS260 series).

Image Gallery - Issue 396