Measuring spatial information changes using Kappa coefficients: A case study of the city groups in central Liaoning Province

To analyze the landscape change of city groups in central Liaoning Province, we classified the remote sensing images of 1988 and 1998 into 12 cover types., The transformation matrix between each two stages was created in GIS (Geographical Information System). Marsh disappeared from the landscape and reed fields showed a declining trend (only remained 6.13%) in this period and could disappear in future. The most change was seen from sandy land which increased by 397.39% and the least change was seen for the cultivated land that decreased by only 2.85%. The result showed that dominant types could change to many classes, but the minor cover types could only transform to a few classes. For example, cultivated land transformed into 10 classes within this ten years. The transformation rates were stable between some cover types, but were not stable between the other cover types. However, the rate and classes for a particular class to transform to were determined by the policy and landscape pattern. The transformation matrix shows that the urban and rural area increased by converting from the cultivated land, while the vegetable land increased with the increasing population. The transformation rate and dynamic shows that the more dominant the classes were in the landscape, the less they would transform into other classes. The indices of Kappa coefficient family decreased within this period. Kappa coefficient for quantity decreased to 96.14%, which means only 96.14% information on quantity remained and 3.86% information lost in this period. Kappa coefficient for location decreased to 94.05%, which means the landscape retained only 94.05% information on location and lost 5.95% location information in these changes. If the purpose of the study is to examine the information loss on quantity, Kappa coefficient for quantity should be used, whereas if the purpose of study is to examine the information loss on location, Kappa coefficient for location should be used. Standard Kappa coefficient and Kappa for no ability to maintain quantity and no ability to specify location decreased to 90.48% and 93.11%, respectively. In comparison, the Kappa for no ability to maintain quantity and no ability to specify location is better than the standard Kappa coefficient, because it assumes that the landscape has no ability to keep quantity and location. The overall proportion agreement is 93% between two maps and this result means there was no significant change in the landscape. The agreement due to quantity was 25% and the transformation rate due to quantity was 3%. And also the agreement due to location was 60% and transformation rate due to location was 4% in this period. The agreement due to chance was 8%, because the whole class number was 12. Therefore, the overall proportion agreement is determined by the agreement due to location.