After classification, accuracy assessment is generated for all classified imagery to assess the classification accuracy based on testing samples. Congalton and Green (1999) indicated that the testing sample size with a minimum of 50 samples for each class should be selected in terms of cost-effectiveness. In addition, both QuickBird imagery for 2006 and Google Earth imagery for 2015 were used to randomly select testing samples over 600 pixels (100 samples for each Level-2 class) in order to obtain reliable accuracy assessment for both years. Moreover, selected samples are manually validated. The error matrices therefore are generated, which contain the overall accuracy, the user’s accuracy and the producer’s accuracy (Congalton, 1991). The user’s accuracy means the probability that a pixel is class A given that the classifier has determined the pixel into class A, while the producer’s accuracy indicates the probability that the classifier has labeled a pixel into class A given that the ground truth is class A (Jensen, 2004).