Method of returning to a last point in a path after a temporary discontinuance of an operation

In conjunction with an operation of directing a vehicle along a plurality of parallel paths in a predetermined pattern utilizing electronic positioning apparatus, including means for periodically measuring the distance of the apparatus from each of two spaced apart reference stations and periodically calculating the position of the vehicle relative to the two spaced apart reference stations, a method of returning to a last point in a path of the pattern after temporary discontinuance of the operation, comprising the steps of:

• (a) defining a coordinate system in conjunction with the predetermined pattern with the paths of the pattern extending generally parallel to a first axis thereof and the second axis lying perpendicular to the paths;
• (b) providing continuous indications of deviations of the vehicle from a path parallel to the first axis and continuous indications of distance of the vehicle along the path relative to the second axis using the calculated positions translated into the coordinate system;
• (c) temporarily discontinuing the operation of directing the vehicle at a point along the path and leaving the path;
• (d) redefining the coordinate system so that a predetermined point therein coincides with the point of discontinuance of the operation;
• (e) returning to the approximate area of discontinued operation and using the deviation indications to direct the movement along the path;
• (f) providing continuous indications of distance of the vehicle along the path relative to the redefined coordinate system;
• and
• (g) reinitiating the operation as the distance indications coincide with the predetermined point of the redefined coordinate system.