Best I can find is that a "sail line" is planned course to be navigated with reference to a specific geographic location.
The only place I saw the term being used was in sites used by agencies and organizations involved in mapping or sounding ocean depths. The sail lines refered to their planned rastor pattern to cover areas pf the ocean floor
GShanks -
Are you asking about what guidlines the USACE determines where the "center of a channel will be loctaed?
