LARGE-AREA VEGETATION MAPPING IN THE GISBORNE DISTRICT, NEW-ZEALAND, FROM LANDSAT TM

Debate over a forestry incentive scheme in the Gisborne district, New Zealand, highlighted the need for up to date information on the vegeta tion cover. Maps of vegetation at a scale of 1:100 000 were produced b y automatically classifying Landsat Thematic Mapper (TM) imagery. The classified imagery was compared with existing vegetation information ( 20-years-old) from a GIS database to identify gross errors. Through fi eld checking the discrepancies were identified as either real changes or errors in classification. Correction of errors increased the overal l classification accuracy from 84 to 90 per cent. The digital vegetati on map was intersected with land use suitability data to provide a two -way table that provided land managers with quantitative information s uitable for making regional planning decisions. Although the 90 per ce nt accuracy is high enough to permit the calculation of vegetation are as and to achieve an adequate representation of regional vegetation pa tterns, it is not high enough to permit the digital vegetation map to be used as a vegetation database where point queries are important.