Data products from the Skylab Earth Resources Experiment Package were examined monocularly or stereoscopically using a variety of magnifying interprctation devices. Land use, forest types, physiographic sites, and plant communitics, as well as forest stress, were interpreted and mapped at sites in Georgia, South Dakota, and Colorado. Microdensitometric techniques and computer-assisted data analysis and sampling procedures were developed and tested against ground truth. Results indicate that only Skylab S190B color photographs are good for classification of forest and nonforest land (90 to 95 percent correct). Both visual and microdensitometer techniques can separate range plant communities at the Region level (ECOCLASS system) with over 90 percent accuracy. Only mountain pine beetle infestations more than 26 m (85 ft) long could be detected. In a study near Redding, California, radiance from Skylab S190B and LANDSAT sensors was found linearly correlated with terrain reflectance.