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The Cantino planisphere focuses on coastlines and how they relate to compass directions as indicated by the lines that crisscross the surface, called rhumb lines. This visual language stems from portolan charts
A rhumbline network (or windrose network) is a navigational aid consisting in multiple lines in a web-like grid drawn on portolan charts (and other early maps ). These nautical charts were used in the medieval age and age of exploration in marine navigation .
Rhumb lines. Portolan charts are characterized by their rhumbline networks, which emanate out from compass roses located at various points on the map. The lines in these networks are generated by compass observations to show lines of constant bearing.
A rhumb line appears as a straight line on a Mercator projection map. [1] The name is derived from Old French or Spanish respectively: "rumb" or "rumbo", a line on the chart which intersects all meridians at the same angle. [1]
Units of distance and speed. True and magnetic courses. Great Circle & Rhumb line. Tracks. Relative bearings: Zone time system. 2. CHARTS. Mercator. Gnomic. Gridded charts & maps. Plotting diagram. Practical work. Use of parallel rulers & Dividers. Plotting positions and tracks on Mercator’s chart using true and magnetic (compass) courses. 3.
28 lip 2019 · First, Mercator figured out how to “flatten” the earth so one could draw a strait line (in navigation terms a rhumb line) on the chart. Second, he built on the work two Greek mathematicians – Erastothenes and Hipparchus – to draw lines of latitude and longitude on his new type of chart.
Around 1540 a debate took place between Pedro Nunes and another Portuguese scholar on the mathematical properties of rhumb lines and the making of rhumb tables. The scholar (whose name is unknown) compiled a treatise on how to draw rhumb lines on a globe on which he heavily criticized Nunes's work.
