The modern Mercator grid system was not invented until 1559, so the ancient surveyors had to develop a method of their own.

Any cartographer or navigator could therefore lay out a Mercator grid for himself by consulting the table.

The datum shift for the Universal Transverse Mercator grid is different.

Universal Transverse Mercator Grid.

Universal Transverse Mercator Grid Tables For Latitudes 0 -80 International Spheroid (Meters).

Overhead, visual displays flashed on the inverted dome of the command center ceiling, showing mercator grid projections, models of activity in the Solar System, and current military hotspots.

On Jennifer's map the sinuous curve of the Americas, the Scandinavian hump, even the six states of Australia were correctly proportioned on a Mercator grid.