Basic Geospatial Network

The BGN provides a national coverage of control marks (including the offshore islands and Antarctica) to enable users to efficiently connected to official geodetic and vertical datums.

It is intended to form a minimum coverage of control marks across New Zealand, its offshore islands and the Ross Sea Region. In most cases the BGN requirements will be met by marks from other control networks. Major uses of this network are to support the registration of aerial and space-based imagery and to enable the consistent mapping of features and objects. The following page summarises the main characteristics of the network.


To provide marks to enable non-cadastral survey users to connect their datasets to official geodetic and vertical datums


Mainland New Zealand and offshore islands

  • 50 km of one BGN mark
  • 100 km of three BGN marks

Ross Sea Region where topographic mapping is provided

  • 100 km of one BGN mark
  • 200 km of three BGN marks


Order: 5

Tier: Horiz C (0.15 m), Vert F (0.35 m)

Class: Horiz VIII (0.01 m, 5x10-5m/m), Vert IX (0.02 m, 1x10-4m/m)

Class evaluation radius: 0.3 km (urban), 1 km (rural)

Mark characteristics

Campaign GNSS

Overhead imagery identification


Sited so that surveyors can easily and safely locate and occupy

Sited for easy identification on overhead imagery

Suitable for collecting GNSS observations

Mark access

Physical access to marks to collect GNSS observations

Visible from afar to enable overhead imagery identification (New Zealand and offshore islands only)