ABSTRACT
The practice of remote sensing relies not only upon acquisition of imagery but also upon our ability to extract useful information from image data, so that users can receive reliable information relevant to their needs. Even a novice can easily realize that a remotely sensed image conveys a wealth of information. Yet, one of the most obvious advantages of remotely sensed imagery-that it conveys this wealth of multifaceted information-forms one of the principal obstacles for those who use
19.1 Visual Interpretation ....................................................................................364 19.2 Information Extraction by Image Interpretation ......................................... 365
19.2.1 Elements of Image Interpretation ................................................. 365 19.2.2 Interpretation of Digital Imagery .................................................. 368
19.2.2.1 Image Enhancement ..................................................... 368 19.2.2.2 Spatial Filtering ............................................................ 370
19.2.3 Who Can Implement Manual Interpretation? ............................... 371 19.3 Information Extraction by Spectral Analysis .............................................. 372
19.3.1 Vegetation Indices ......................................................................... 372 19.3.2 Digital Image Classifi cation ......................................................... 374
19.3.2.1 Informational Classes and Spectral Classes ................. 377 19.3.2.2 Supervised Classifi cation and Unsupervised
Classifi cation ................................................................377 19.3.2.3 Classifi cation Algorithms ............................................. 379 19.3.2.4 Who Can Execute Digital Extraction
of Image Information? ..................................................382 19.4 Extracting Temporal Information ................................................................ 382
19.4.1 Data for Temporal Analysis .......................................................... 383 19.4.2 Sequential Aerial Photography ..................................................... 383 19.4.3 Digital Change Analysis ...............................................................384 19.4.4 Land Surface Phenology ............................................................... 386
19.5 Summary ..................................................................................................... 388 References .............................................................................................................. 389
the imagery, as this information is interwoven with many other forms of information that may not be relevant for the purpose at hand.
