By David Pairman
New Zealand’s Landcover Database v3.0 (LCDB3) was released at the start of July 2012 and is now available on the LRIS download portal.
LCDB v3.0 has been compiled by staff within the Informatics team over the past year from about 160 satellite images of New Zealand that were captured in the summer of 2008/9. With 431,666 polygons, the database classifies all land cover under 33 different classes at three nominal summer periods (1996/97, 2000/01 and 2008/09).
It is a little difficult to dissect the change statistics into contributing factors as the LCDB v3.0 was produced by a mix of many processes. Some were automated such as the pre-processing to smooth stepping artefacts, and post-processing to align with the Topo50 coastline, while other involved operators interpreting imagery. On top of this some processes were done on regional data sets before final compilation as a national data set for the coastline adjustments. Even after that there was manual editing to fix a few glitches. During the manual mapping stage some areas needed rubber-sheeting where the version 2 of the Landcover Database (LCDB2) was found to be misregistered.
Around 64,000 polygons were manually modified in this revision with about 36% of these being real change between 2000/01 and 2008/09 and the remainder being corrections on previous mapping. About 3000 of the manually modified polygons were as a result of checking or other information by regional councils, territorial authorities and DOC. A further 215,000+ polygons or polygon parts were modified by semi-automated adjustments (excluding smoothing artefacts) to make the dataset more compatible with others. This includes some rubber sheeting and the Topo50 coastline adjustments. However, if you simply take a union of the final product with the LCDB2 (pre- step artefact smoothing), then there are over 13 million polygons changed!
Further information on the LCDB can be found on the LCDB website.