The New Zealand Land Resource Inventory (NZLRI) is a national database of physical land resource information. It comprises two sets of data compiled using stereo aerial photography, published and unpublished reference material, and extensive field work:
1. An inventory of five physical factors (rock type, soil, slope, present type and severity of erosion, and vegetation). A 'homogeneous unit area' approach is used to record the five physical factors simultaneously to a level of detail appropriate for presentation at a scale of 1:50,000.
2. A Land Use Capability (LUC) rating of the ability of each polygon to sustain agricultural production, based on an assessment of the inventory factors above, climate, the effects of past land use, and the potential for erosion. The NZLRI covers the country in 11 regions, each with a separate LUC classification.
The first edition NZLRI provides national coverage from mapping between 1973 and 1979 at a scale of 1:63,360. A limited revision regional upgrade of the north Waikato area was completed at a scale of 1:63,360 in 1983. Second edition NZLRI regional upgrades at a scale of 1:50,000 have been completed for Northland, Wellington, Marlborough and Gisborne-East Cape. Third edition NZLRI layers contained a restructured polygon attribute table to allow the core NZLRI to complement the newly created fundamental soil layers with minimal duplication.
The first edition NZLRI provides national coverage from mapping between 1973 and 1979 at a scale of 1:63,360. These data were digitised for GIS retrieval in 1981 (Version 1.1).
A limited revision regional upgrade of the north Waikato area was completed at a scale of 1:63,360 in 1983. (Version 1.2).
A polygon boundary and attribute validity edit over the whole database was completed in 1992. Attributes to accommodate second edition classifications were added in preparation for incorporating 1:50,000 remapping (Version 2.1).
Second edition NZLRI regional upgrades at a scale of 1:50,000 were completed for Northland in 1988 and Wellington in 1991and incorporated into the database (not present in this layer) in 1992. (Version 2.2).
A second edition NZLRI regional upgrade at a scale of 1:50,000 was completed for eastern Marlborough in 1995 (Version 2.3).
A second edition NZLRI regional upgrade at a scale of 1:50,000 was completed for Gisborne-East Cape (not present in this layer) in 1999 (Version 2.4).
In 2000, at the time the first generation fundamental soil layers were created, the (mainly soil elements of the) polygon attribute table was restructured so that the two datasets would be complementary with minimal duplication (Version 3.1).
Incidental error correction has occurred as necessary.
Survey date, and therefore currency of data, varies from 1973 to 1998. Rock, Soil, and Slope are less affected by survey date than vegetation and erosion.
The multi-factor, homogenous unit area mapping, method tends to result in themes being delineated at lower resolution than a single factor map of equivalent scale. Erosion and Vegetation were often recorded within units defined primarily on the basis of Rock, Soil, and Slope.
While mapping scale remained constant (at 1:63,360 and later 1:50,000), polygon resolution increased in detail as the survey progressed, and was variably constrained by the quality of source information available to the mapper.