Читать книгу Imagery and GIS - Kass Green - Страница 25

A subset of thematic maps is feature maps. Rather than label the entire landscape, feature maps identify only a single object type, resulting in a binary map in which the feature is located and identified, and everything else is mapped as null; not that feature. Often, the feature of interest is a very specific type of object such as an airplane, military vehicle, or other unique entity that is out of place and unexpected in a particular environment. Sometimes, the objects of interest are common objects such as water bodies, roads, or buildings. Feature extraction is usually performed manually, but computer algorithms have also been developed to automatically extract features. Usually, automated feature extraction results in a number of false positives (i.e., the location of points that are not the feature of interest), which are then manually reviewed and corrected.