We used Texas Instruments DS990 computers, a basic operating
system, and eight inch dual floppy discs, with no hard drive. The
map combining process was two maps at a time..., to produce a third.
The resulting map was combined with perhaps the product of two other maps,
The process had over 10 combining steps and 63 15 minute
quad sized maps per combining step. I do remember taking 8 months
just to produce (print) the black and white maps (as composite of overstrike