Often many different crops are planted in a single small area; small towns and large urban areas are not clearly defined and often are mixed together; and there are rapid changes in construction. These make it difficult to interpret satellite images.
一小塊地常常種植不同的作物，鄉間和都市的區別也不明顯，常常混在一起，再加上工程上的變動，會造成衛星判釋上的困難。