Acquisition et controle des donnees par photogrammetrie numerique a grande echelle

Abstract

Digital data acquisition techniques through large-scale photogrammetry are reviewed, including not only data measuring and recording, but also checking and editing, since these phases have to be performed before inserting data into data banks, and automatic compiling and plotting as well. Various methods of acquisition and editing in use at the time fall into several categories, based upon different criteria: direct or indirect acquisition (direct from the stereomodel, indirect from an intermediate two-dimensional support), the degree of automation according to the nature of the desired informations, and the role of the computer (off-line or on-line) in correlation with new man-machine relationships. In conclusion, the author attempts to report significant trends such as: 1. (1) automation seems to develop particularly for altimetric data, directly digitized from the model, in connexion with automatic orthophotography, on-line or off-line print; 2. (2) planimetric features are also digitized directly from the model, with human interpretation and computer assistance, and in the most recent systems CRT displays and interactive data manipulation; 3. (3) however, many organizations use two-dimensional digitization from existing linemaps or orthophotographs, and display and editing procedures by batch processing; 4. (4) from a theoretical point of view stereoorthophotographs offer an intermediate solution with many advantages, since they are both planimetric and altimetric, can be digitized both in two or three dimensions and be entirely automatically produced; 5. (5) two series of problems still limit automation in large-scale photogrammetric digitizing and editing: automatic interpretation or pattern recognition, which is a general problem of image processing; and automatic revision, which is a general problem of data banks.