In North Korea, the shortage of food has been a serious problem for the past several years. However, the actual condition of present North Korea cannot be investigated there. Then, it analyzes about the food situation of North Korea from a viewpoint of vegetation using the remote sensing technology using the satellite. In Tohoku University, NOAA AVHRR images are accumulated over the past ten years or more. It can study for the difference between present and the past in analyzing vegetation over a long term. We analyze vegetation in Korea using NOAA-11,14 and 16 from 1989 to 2002. As a satellite is employed over a long term, a sensor will deteriorate. So, it is necessary to calibrate degradation of a sensor. And also the observation range of wavelength is different for some NOAA satellites, we calibrate the data to keep a reliability.