Computer-Assisted Photo Interpretation Research at USAETL

Abstract

A program in comouter-assisxed Photo interpretation research (CAPIR) has been initiated at the U.S. Army Engineer Topographic Laboratories. In a new laboratory, a photo inter- Spreter (PI) analyzing high-resolution, aerial photography interfaces directly to a digital computer and geographic information system (IS). A modified analytical plotter enables the PI to transmit encoded three-dimensional spatial data from the stereomodel to the com- puter. Computer-generated griphics are displayed in the stereomodel for direct feedback of digital spatial data to the PI. Initial CAPIR capabilities include point positioning, . mensuration, stereoscopic area search, GIS creation and playback, and elevation data extrac- tion. New capabilities under development include stereo oraohic supernosition, a digital image workstation, and integration of panoramic Optical Bar Camera photography as a primary GIS data source. This project has been conceived as-an evolutionary approach to the dig- ital cartographic feature extracjtE L problem. As a working feature extraction system, the CAPIR laboratory can serve as a testbed for new concepts emerging from image understanding and knowledge-based systems research. The primary data source for these digital products is stereoscopic aerial photography acquired by modern mapping and reconnaissance caneras. With the notable exception of stereocorrelation equipment, extracting information from imagery is a labor-intensive, man- ual process conducted by specialists interpreting stereo aerial photography to produce intermediate manuscripts and associated data lists (Case, 1981). -manual digitization is used to convert manuscripts into machine-readable formats. Further processing is required to assemble, edit and check the derived data for production of specified digital products. Long-term data maintenance, update and quality control requirements are currently addressed using similar labor-intensive mtthods. It is obvious that a substantial gap exists between current manual image analysis procedures and the requirements to produce large volumes of digital cartographic data. The U.S. Army Engineer Topographic Laboratories initiated a program in computer-assisted photo interpretaticn research (CAPIR) which addresses this problem. The central objective is to support the human specialist with hardware and software that will make information extraction from stereoscopic aerial photography that is simpler, faster and more accurate than existing Atanual photo interpretation procedures. The explicit intention of the program