- 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)
- This a Roman Chart that listed the parallels of Latitude and Longitude in the known world.
- Roman Prime Meridian
- In Ptolemy’s Geographia (c.150 CE), the Roman Prime Meridian or Zero Degree Longitude, was centred on Mount Teide in Tenerife.
- Parallel of Rhodes
- The Parallel of Rhodes was one of 33 Parallels of Latitude described by the Roman Geographer, Ptolemy who was influenced by Eratosthenes.
- It is almost exactly the Parallel of 36 degrees North which runs from Gibraltar to Rhodes and could be used for east-west Navigation.
- Roman Prime Meridian
Roman Navigation Instruments
- Gnomon
- 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- The Astrolabe superseded the Gnomon, by bringing together the Gnomon and the Star Chart, built into one instrument.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
Roman Lighthouses
- The Romans built lighthouses across the Roman Empire. They were usually modeled on the Pharos of Alexandria in Egypt.
- La Coruna Roman Lighthouse in Spain is still in use today.
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
- Pliny the Elder (23-79 CE) described in detail the sea journey from Egypt to India in Book VI of his Natural History.
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.