A methodology was developed to evaluate the accuracy of maps of land-cover
change produced from multi-temporal Thematic Mapper images for Australia. T
he methodology is based on 500-pixel-by-500-pixel areal sample units. Sampl
es units were selected in a two-stage procedure that first ensured that a c
ertain number were selected for which change was apparent on the change map
being evaluated. The remaining sample units were then selected according t
o a spatially distributed random sample without replacement. An independent
estimate of change was obtained for each sample unit by a human operator u
sing one or more image enhancement techniques to determine subjectively how
much change occurred. Confidence intervals for an increase and a decrease
in woody vegetation were calculated on the independent estimate of change a
nd the amount of change on the original map compared against them. To obtai
n stable confidence intervals, the method requires that 33 samples per chan
ge map/TM image are examined for each map of land-cover change, something t
hat requires approximately two person-days per change map. The methodology
was found to be robust for change maps on which change was relatively rare
(about 0.13% of the total change map) and also for those on which change wa
s relatively common (about 2.5% of the total change map).