Roman Navigation

  • In the Mediterranean, the Romans mainly navigated along the coastlines by day and by night. They used Lighthouses to guide them into the harbours.
  • Roman merchant ships were square rigged sailing vessels and the Roman captains used a guide called a Periplus that gave details about the ports and coastal landmarks.

The Periplus

  • The Periplus was a Sea Guide for Sailors in the Ancient World, known today as a Pilot or Nautical Almanac.
  • It was a document that showed Ports and Coastal Landmarks sequentially to the captain, including information about local hazards, the local tribes, expected weather and the presence of pirates.

Ptolemy's Geographia (c.150 CE)

Roman Navigation Instruments

  • Gnomon
    • A Device used in the Ancient World to measure the height and angle of Celestial Objects, mainly the Sun, but also Moon and Stars.
  • Astrolabe
    • The Astrolabe was a device used in Celestial Navigation to calculate the user’s Latitude and local time. Astrolabe means ‘star-taker’ in Greek.
    • The Astrolabe superseded the Gnomon, by bringing together the Gnomon and the Star Chart, built into one instrument.
  • Roman Sundial
    • The Roman sundial was either a semicircular dial or a concave hemispherical surface with a nodus that measured the sun’s shadow. They also had small portable sundials.
  • Moon Dial
    • A basic Moondial is identical to a Sundial but is only accurate when used on the night of a full moon.
  • Antikythera Mechanism
    • The Antikythera Mechanism is the world’s oldest known geared device dating from c. 87 BCE.
    • In his De Re Publica, Cicero refers to an Orrery which predicts the positions of the Sun and the Moon and the eclipses of both, and also the five known Planets of that time.

Roman Lighthouses

Roman Sea Law

  • Roman Sea Law defined the Use of the Sea and how commerce and shipping should be conducted.
  • It was based on the much older Rhodian Sea Law.

Mare clausum

  • Between November and March the Seas were considered too dangerous to navigate safely, and were officially closed.
  • The term ‘Mare Clausem’ is still used in International Law today to mean a closed Sea.

Roman Wind Rose

  • The Roman Wind Rose was the Greek Wind Rose reduced to 8 Winds with Latin Names.
  • However, Seneca listed 12 winds and Vitruvius listed 24 winds.
  • Tower of Winds in Athens, is an octagonal tower with a wind vane pointing to eight winds.

Celestial Navigation

  • Celestial Navigation is a method of orientation by using the stars to locate the traveller’s position when crossing land and oceans without a compass.
  • It has been in use since antiquity by the Ancient Egyptians, Greeks and Romans.
  • Sidereal Compass
    • The Sidereal Compass means navigating by the stars, instead of using a magnetic compass. Sidereal is from the Latin Sidus meaning star.
    • The Sidereal Compass rose has compass points that indicate the rising stars on one side and the setting stars on the other.
  • Navigating using the Moon
    • The Moon is always visible except for 4 nights in a month. It acts as a compass, as a clock, as a calendar and it provides light for 4 nights every month.

Roman Flag

  • Standards were flown from Roman vessels, but it is not known whether they carried the Roman Flag or Vexillum, like the Legions or modern shipping.

Roman Shipping

  • The Romans had an extensive knowledge of different shipbuilding techniques.
  • This is revealed in a Roman mosaic excavated in a 2nd century CE bath house in Althiburus, Tunisia.
  • The mosaic displays 25 different ship types with their names, from small to medium naval, cargo, fishing and pleasure boats, used both at sea and on rivers.
  • Giant vessels were also used by the Roman Grain Fleets to carry grain to Rome.

Pliny's Description of the Route to India

Roman Canals

  • The Romans built many canals for irrigation and to control flooding in deltas, but also for navigation.
  • Lakes, streams and rivers were diverted along canals to enable vessels to travel considerable distances.
  • Trajan even built a Suez Canal (c.112 CE) connecting the Nile with the Red Sea.

Points of Sail

  • A Point of Sail is the direction of a sailing vessel under sail in relation to the direction of the true wind.

Nautical Dictionary

  • The modern Nautical Dictionary holds technical terms applicable to sailing vessels, seamanship and navigation, which would also have been used in the Roman Period.

Weather Phenomena

  • St. Elmo’s fire
    • This is an electrical discharge which becomes visible as a blue light when thunderstorms are nearby and electricity is induced to discharge itself from sharp points, such as the masts and spars on a vessel.
    • The Ancient Greek and Roman sailors reported seeing the lights, and optimistically believed they were a visitation from the twin Gods, Castor and Pollux, who were thought to be the saviours of those in danger.
  • Flying Dutchman
    • This is an optical illusion or mirage consisting of seeing a ship which appears either in the air with its reflection, or upside down in the air, long before it physically makes its appearance on the ocean.
  • Tropical Cyclones
    • A Tropical Cyclone, also known as a Hurricane or Typhoon, is a low pressure rotating storm system which occurs mainly in the Indian Ocean and the South China Sea.
  • Monsoon
    • The Monsoon is a Tropical Wind that changes direction every six months due to the heating or cooling of the land masses.
    • It affects Africa, the Indian Ocean, India and Australia. The Monsoon continually varies in rainfall, and can cause either drastic flooding or severe drought.
    • The southwest Monsoons brought Roman ships emerging from the Red Sea to India in around 45 days.
    • The northeast Monsoons sent the ships home from India back to the Red Sea.

 

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