I found this interesting historic map at a History of the Atlantic Cable & Undersea Communications from the first submarine cable of 1850 to the worldwide fiber optic network site. This site also has other historic Submarine Cable Route Maps, too.
This is an early Plan and Profile , or "Vertical Section" as it is noted on the plan, showing the bed of the Atlantic Ocean from Valencia, Ireland, to Trinity Bay, Newfoundland from 1857. This survey, or map, shows the surveyed soundings made by Lieut. Dayman in H.M.S. Cyclops, 1857,
for laying the Atlantic Telegraph Cable.
Due to the relationship of ocean depths of the surveyed soundings and overall horizontal distance covered, the vertical scale is 72 times greater than the horizontal (longitudinal) scale. I guess that with an engineering project like this a 50 horizontal/4 vertical scale just wouldn't cut it.
Professional Land Surveyor source: http://www.atlantic-cable.com/Maps/