Spanish to English Science Environment & Ecology aquatic resources - de Uruguay

Underneath the heading of "CALADA" is indicated the degree heading of a vessel along with the date and time.

The next heading is VIRADA, or "tack" for nautical usage according to the Oxford Dictionary. The Random House defines "tack"" as follows:

aut.
a. a rope for extending the lower forward corner of a course.
b. the lower forward corner of a course or fore-and-aft sail. See diag. under sail.
c. the heading of a sailing vessel, when sailing close-hauled, with reference to the wind direction.
d. a course run obliquely against the wind.
e. one of the series of straight runs that make up the zigzag course of a ship proceeding to windward.

Underneath "VIRADA" are the subheadings of fecha and hora.

In this context, juxtaposing "calada" with "virada" and the usage with the degree marking the vessel as well as the date and time under both headings, I am trying to get an appropriate translation of "calada".

Thank you for your help.

Mike :)