2.4. Accuracy assessment
We randomly generated 500 points in the study area using ArcGIS9.3 software, and imported them into the layer-stacked image of the five TM images from different seasons in 2004. By combining and showing different bands of the stacked TM image in RGB, we visually interpreted and selected 333 validation samples from points that R406 were homogenous within 9 × 9 pixels of TM around those samples (Table 1). The samples were used to calculate the confusion matrix of the 2004 MODIS classification result. Supplemental data of water level were also applied, to compare with areas of different land covers.
Table 1.
Number of validation samples used to calculate confusion matrix for MODIS classification result of year 2004.Land cover typesNumber of samplesWater82Mudflat84Submerged vegetation103Emergent vegetation64Full-size tableTable optionsView in workspaceDownload as CSV
2.5. Changes of different land cover types
Both area and its corresponding proportion of different land cover types were calculated. In addition, temporal area changes of thecodonts types were statistically analyzed, to detect inter-annual changes of wetland cover types from 2000 to 2012.
We randomly generated 500 points in the study area using ArcGIS9.3 software, and imported them into the layer-stacked image of the five TM images from different seasons in 2004. By combining and showing different bands of the stacked TM image in RGB, we visually interpreted and selected 333 validation samples from points that R406 were homogenous within 9 × 9 pixels of TM around those samples (Table 1). The samples were used to calculate the confusion matrix of the 2004 MODIS classification result. Supplemental data of water level were also applied, to compare with areas of different land covers.
Table 1.
Number of validation samples used to calculate confusion matrix for MODIS classification result of year 2004.Land cover typesNumber of samplesWater82Mudflat84Submerged vegetation103Emergent vegetation64Full-size tableTable optionsView in workspaceDownload as CSV
2.5. Changes of different land cover types
Both area and its corresponding proportion of different land cover types were calculated. In addition, temporal area changes of thecodonts types were statistically analyzed, to detect inter-annual changes of wetland cover types from 2000 to 2012.