Scanning Cursor Device.

摘要

A developmental model of an aided-track digitizing cursor used in conjunction with a digitizing table is described; this cursor can significantly increase the efficiency of digitizing graphic materials. The cursor incorporates a rotatable linear photodiode array onto which the feature being digitized is imaged. Processing of the array output produces a count indication of the deviation of the feature from the table encoder fiducial marking. A dedicated minicomputer is used to combine the digitizing encoder outputs with the array correctional counts to derive accurate coordinate values in the presence of tracking errors up to 1/16th inch. Rotational commands are generated by the computer to orient the array perpendicular to the traced feature for maintaining accuracy in cases where curvatures exist in the traced function. Rotation through + or - 360 degrees permits closed contours to be traced with no sacrifice in encoding accuracy. Preliminary tests have shown correctional accuracies of better than + or - 4 mils can be achieved with the system, equaling the resolution accuracy of the digitizing table. Algorithms and software developed for this device allow compatible operation with the Lineal Input System (LIS) used in generating cartographic materials. The LIS System was developed by the Experimental Cartographic Facility, RADC, Griffiss Air Force Base, NY. (Author)