Image Analysis, Classification and Change Detection in Remote Sensing, 3rd Edition

266 Supervised Classification Part 1

the availability of a second dataset, which is usually referred to as the valida-

tion dataset. An optio n in the ENVI/IDL neural network program described

in Appendix C allows the training data to be split in two, so that half the data

are reserved for validation purposes. (If test data were held back, the training

dataset is then one third of its original size.) Both ha lves are still represen-

tative of the class distributions and are statistically independent. During the

training phase, which is carried out only with the training data, cost functions

calculated b oth with the training data as well as with the ...