2. Study area and data
2.1. Study area and ground survey
The study area is selected in North China region, correspondingto path 123 and row 31 of Landsat ETM+ data. To weaken the influ-ence of Landsat ETM+ gaps on classification accuracy, a rectang leregion is subset as the final study area, which lies between approxi-mately 40◦6N to 42◦4N, and 116◦3E to 117◦7E . The studyarea mainly consists of Weichang, Fengning, Longhua, Duolun andLuanpin counties of China. It belongs to semi-humid and semi-dryclimate region at temperate zone. The annual precipitation is about500 mm, of which 80% falls in the period of July to September.The annual average temperature is about −1.4 to 4.7◦C, and theannual accumulated temperature above zero is 2000–2200◦C. Fourseasons are evident, and wet and hot in the summer, cold in theFig