A NUMERICAL METHOD OF ORIENTATION FOR THE KELSH PLOTTER

IN LARGE SCALE PHOTOGRAMMETRIC PLOTTING, PARTICULARLY IN THE FIELD OF HIGHWAYS, THE KELSH PLOTTER IS ONE OF THE MOST COMMONLY USED INSTRUMENTS IN NORTH AMERICA. AT PRESENT A SIGNIFICANT AMOUNT OF WORK TIME IS STILL BEING SPENT ON MODEL ORIENTATION. ONE DISADVANTAGE IN PRESENT TRIAL-AND- ERROR PROCEDURES IS THE NECESSITY OF REPEATING THE ORIENTATION PROCEDURES FOR RELATIVE AND ABSOLUTE ORIENTATION A NUMBER OF TIMES BEFORE Y-PARALLAXES ARE REMOVED AND BEFORE SCALE AND ELEVATION DIFFERENCES ARE ELIMINATED BETWEEN MODEL AND CONTROL POINTS. SUGGESTIONS FOR APPLYING NUMERICAL ORIENTATION TO KELSH PLOTTERS WITHOUT MODIFICATION OF THE INSTRUMENTS ARE GIVEN. SUCH NUMERICAL ORIENTATION CAN BE APPLIED TO RELATIVE ORIENTATION ACCORDING TO MEASURED PARALLAXES, TO ABSOLUTE ORIENTATION ACCORDING TO CONTROL POINTS, AND TO SETTING OF PRECOMPUTED ORIENTATION ELEMENTS, DETERMINED FROM INSTRUMENTAL OR ANALYTICAL AERIAL TRIANGULATION. THE LATTER TWO APPLICATIONS WILL BE MOST ECONOMICALLY SIGNIFICANT, WHILE THE FIRST WILL BE OF INTEREST IN AREAS WHERE TRIAL-AND-ERROR RELATIVE ORIENTATION HAS A SLOW RATE OF CONVERGENCE, SUCH AS HILLY TERRAIN.