Reading: Multiple Choice: Question 4

From roughly the late thirteenth century onward, Mediterranean sailors navigated using a distinctive style of nautical chart known as a portolan chart. Unlike later maps built around a grid of latitude and longitude, a portolan chart is organised around a dense web of straight lines, called rhumb lines, radiating outward from a series of compass roses printed across the sheet. A navigator laid a straightedge along the rhumb line closest to the intended course, read off the compass bearing it represented, and steered accordingly.

This method, known as dead reckoning, combined a magnetic-compass heading with an estimate of the distance travelled, based on elapsed time and the ship's known speed, to plot an approximate position without any reference to the stars or the sun. Coastlines on these charts were often drawn in exaggerated, sharply defined detail, crowded with the names of harbours and headlands written perpendicular to the shore, while the interior of any landmass was frequently left blank or filled only with decorative flourishes, since it held no relevance for a sailor hugging the coast.

Chart-making workshops in cities such as Genoa, Venice and Palma de Majorca originally produced portolan charts purely as practical trade tools for working sailors. Over the following centuries, however, some workshops also began producing lavishly illustrated versions, decorated with miniature ships, sea monsters and gilded compass roses, commissioned by wealthy patrons as prestige objects rather than as instruments anyone intended to take to sea. The earliest surviving example, known as the Carte Pisane, is generally dated to the closing decades of the thirteenth century.

Portolan charts eventually fell out of use for long-distance navigation once European sailors began regularly crossing entire oceans rather than following coastlines. A chart built from straight rhumb lines on a flat sheet cannot accurately represent a course of thousands of kilometres across a curved surface, and the error this introduced grew too large to ignore once transatlantic and round-Africa voyages became routine, prompting the gradual adoption of charts incorporating map projections and latitude scales.

Choose the correct letter, A, B, C or D.

1. According to the passage, what is the main navigational feature portolan charts are organised around? A. A grid of latitude and longitude lines. B. Depth soundings marked at regular intervals along the coast. C. Networks of straight rhumb lines radiating from compass roses. D. Astronomical star charts printed alongside the coastline.

2. According to the passage, how did sailors typically determine their position using these charts? A. By following compass headings and estimated distances, a method known as dead reckoning. B. By calculating their position from the sun's elevation alone. C. By relying on coordinates transcribed from a printed grid. D. By matching depth soundings to a printed key.

3. What happened to portolan charts over the centuries, according to the passage? A. They remained purely practical trade tools and were never decorated. B. They were banned once printed maps became widely available. C. They were replaced entirely by star charts within a few decades. D. Some became elaborately illustrated luxury items commissioned by wealthy patrons, alongside their practical use.

4. Why were portolan charts eventually superseded for long-distance navigation, according to the passage? A. Because rhumb-line charts became too costly for workshops to produce. B. Because their straight rhumb lines could not properly account for the Earth's curvature on very long voyages. C. Because compasses were no longer used at sea after the fifteenth century. D. Because trade routes shifted entirely from sea to overland routes.