Abstract
This study aimed to estimate onion area based on the spectral characteristics using satellite data. SPOT data were obtained from middle June to middle August in Hokkaido at growth season of onion. The reflectance of the red and near infrared in onion fields was higher than those in other crops, because onion leaves fall down and covered soil surface just before harvesting in late July. Therefore, using the above characteristics, onion classification map was generated by maximum likelihood method of supervised classification. As results, the onion area was underestimated with 15.2% error. The factor of the underestimated area was considered to be missed classification in the areas of boundary of the field. To reduce the error, polygon data for each field in surveyed area were superimposed on the obtained onion classification map and the total field area with predominantly onion was calculated. As a result, the estimated area has high accuracy with 97.8%.From above results, it was clarified that onion area could estimated with high accuracy by combing SPOT data with topographic field data.
