Working from the projected map requires the scale factor in terms of the Mercator ordinate y (unless the map is provided with an explicit latitude scale).

Aitken measured off distances from the latitude scale.

A small adjustable weight on a threaded rod, and a latitude scale makes the gyro precess at the Earth's equivalent angular rate at the given latitude.

Twenty miles at the most, gentlemen.1 He measured off the distance from the latitude scale.

He took a pair of dividers from a rack and set them to a mile on the latitude scale.

And no other port for -"he measured two spread fingers against the latitude scale"-fifty miles either side.

After opening them against the latitude scale he 'walked' them across the chart from the Needles to Ushant, the island just off the northwestern tip of France.

The resulting variation of the latitude scale is shown on the meridian at 350 E of his map.

However he proceeded, Mercator achieved a fairly accurate, but not perfect, latitude scale.

Southwick continued looking at the chart and, using his finger and thumb, measured a distance against the latitude scale.