Let’s have a closer look at sailing these ancient ships.
How about the wind?
Wind force. Sailing was (and still is) considered comfortable with winds of Force 3-4 Beaufort (up to 15 knots), it becomes quite ‘sportive’ with Force 5-6 Bft and critical above Force 7 Bft (over 30 knots). According to Pascal Arnaud (2005, p 22), as long as a sea state (wind and waves) does not exceed say Force 4 Bft (15 knots wind), the sailor is free to manoeuvre his ship in various directions, but for higher sea states he looses this freedom and has to sail downwind.
The 1986 Kyrenia II experiment (small 30 ton freighter of 14.5 x 4.5 m) has shown that an ancient merchant ship could resist well in a Force 9-10 Bft storm (45-50 knots wind). Surely much better than any ancient battle ship that would probably not resist more than Force 6 Bft (25 knots wind) and 1 m waves, as shown during the Olympias sea trials (50 ton trireme of 37 x 5.5 m) in 1992 (Morrison et al., 2000).
Wind direction. It was mentioned above that, provided the wind force does not exceed 15 knots, the sailor has some freedom as to his direction of sailing. Ships were normally sailing from wind astern (180°) to wind abeam (90°), but it was possible to sail into the wind up to around 60° (see Arnaud, 2005, and Morrison et al., 2000). However, such a close-hauled course was very unconfortable and not very efficient because of the leeway (lateral drift) ranging between 5 and 15°: the course with respect to the wind direction was therefore around 75° (60° + 15° leeway) or 80° (70° + 10° leeway), meaning that only 15 to 10° headway was really made with respect to the ‘no headway’ direction of 90°. This was a lot of effort for small progess in the desired direction (of 0°), and it may be expected that few sailors would choose this sailing technique on a long distance if not forced to do so by unexpected wind conditions.
The points of sail shown above are valid for modern ‘Bermuda’ rigs with a large genoa sail, but ancient ships had square sail(s) or a lateen or settee sail. Modern sailing boats may reach 20-30° as shown above, but they are designed for racing more than for transporting cargo.
If the ship’s destination requires sailing to windward, ‘beating the wind’, then periodic ‘changing tack’ is needed. It consists in zig-zaging on close-hauled courses. The ship’s speed in the desired direction (Vmg, ‘Velocity made good’) is obviously reduced.
With a square sail, the preferred method for changing tack was by ‘gybing’ (turn the ship to running downwind, then turn her back to a close-hauled course on the other tack).
A merchant sailing ship will show the best performance when sailing at broad reach, but it also needs to show acceptable performance in sailing to windward at close reach with a simple easy-to-build sailing rig.
How about the sailing rigs?
The lateen/settee rig was probably invented in the 2nd c. AD and was widely adopted in the 5th c. AD. This does not mean that square sails were abandoned, as they were still in use on windjammers at the end of merchant sailing in the early 20th c.. Several concepts thus coexisted over very long periods of time (Julian Whitewright, Pascal Arnaud, Rod Heikell ).
The various sailing rigs obviously had pros and cons and mariners made their own choices. Note that modern sailors are biased by the modern triangular Bermuda rig designed for sailing-boat racing in the 19th c..
From a sailors’ point of view, it was worth trying to take the end of the upper yard of the square sail down to the bow to reduce the length of sail-cloth prone to sagging on the luff side. This would probably leave too much sail abaft the mast so that the ship would easily luff, but it opened the way to the triangular shape of the lateen/settee rig pointing into the wind. Furthermore, the lateen sail consisted of less components than the square sail, but it required more crew to be handled.
Whitewright (2011) shows that the lateen and settee rigs performed only very slightly better to windward than square sails as it allowed sailing 55 to 65° off the wind direction, while a square sail would allow 60 to 65°. The ‘velocity made good’ was only 1 to 2 knots in both cases (with moderate wind and calm sea). Hence, there is very little difference in the overall performance of both rigs and this explains why both coexisted for many centuries.
The 5th century Kelenderis mosaic below shows a ship in full action in a rough sea.
Note that although the harbour city is depicted, the ship is sailing in rough seas with many waves. In this picture, you can almost feel the rough sailing conditions at close reach with a reefed sail. Such a picture of a sailing ship in full action is very rare as artists never had an opportunity to see this from the shore.
Sailors are not conservative at all when it comes to sail settings
and they may very well have used the triangular setting of the square sail for many centuries before the Kelenderis mosaic picture.
Sailing on the Mediterranean Sea
The main sailing routes have been deduced from ancient texts (Arnaud, 2005) and from modern ‘Pilots’ used by yachtsmen. Indeed, the meteorological sailing conditions are considered to be fairly unchanged over the past few millennia. Wind speed and direction are of paramount importance for sailing, as Mediterranean currents play a secondary role and high waves are avoided as much as possible.
The prevailing wind direction almost everywhere on the Mediterranean Sea is NW.
Note that ‘prevailing’ usually means ‘over 50% of time’, but not 100%!
In addition, a constant wind direction is required for long-haul offshore sailing. This is typically the case from Sicily to Alexandria in summer time, but other prevailing wind directions may exist locally, e.g. north on the Aegean Sea, north and NE on the Black Sea and east along the coasts of Algeria. Obviously, some finer analysis is needed to find a way back to Rome from Alexandria. This trip is achieved by using sea breezes blowing in the afternoon from the sea to the land. These winds are best felt within a few miles off the coast. They blow more or less perpendicular to the coast, but may locally reach an angle of 45° or even be parallel to the coast.
So here is the conclusion:
Going east can be achieved by long-haul offshore sailing,
and going west has to be done with more coastal navigation.
The trip to Rome is therefore much longer than the trip to Alexandria as it is not only longer in distance, but it also involves much waiting for favourable wind conditions: one or two weeks sailing to Alexandria, but at least double when sailing back to Rome.
The trip from Alexandria to Rome goes north directly to Rhodes, or along the Levantine coast and then west along the southern Cypriot coast, but some will make a direct route to Cyprus using the westerlies. In any case, sailing from Cyprus to Rhodes is difficult due to adverse winds[3a]. The Aegean Sea is famous for its northern wind called Meltemi which makes its east-west crossing a subtle operation using local winds around the islands. The route through the Aegean Sea is still a matter of debate, some favour the northern route, but those not going to Athens prefer the southern route avoiding the dangerous Cape Maleas. West of the Peloponnesus, the Ionian Sea with prevailing NW winds has to be crossed, either directly to the Messina Strait, or by following the Greek coast before crossing over to Calabria. An alternative to this Aegean route is the Libyan route along the coasts of Cyrenaica, Libya and Malta or Tunisia (mainly in May and in October, in order to avoid the northwestern “etesian winds”).
The western Mediterranean is subjected to low pressures travelling from west to east and inducing a counter-clockwise wind pattern. Hence, on the French south coast, the wind will blow from south to east first, then turn to north to NW, generating the famous Mistral and Tramontana. This explains that it can be difficult to sail from Marseille to Cabo de Creus and that this has to be done close to the coast to avoid high offshore waves induced by the Tramontana. The trip back may lead through the Baleares and Sardinia, where the westerlies will prevail, then along the western coasts of Sardinia and Corsica where a southern wind may blow. Those going to Rome will take the dangerous Straits of Bonifacio between Sardinia and Corsica.
The coast of North Africa is prone to summer easterlies between Cap Bon and Oran, but lack of wind between Oran and Gibraltar … in addition to adverse east going surface currents of Atlantic water compensating the Mediterranean evaporation.
The Tunisian Golfe de Gabes and Libyan Gulf of Syrt have a tidal range up to 1 m inducing tidal currents that can be used by sailors in both directions. The summer winds may blow from north to east.
The access to the Black Sea is very difficult because of the strong southward surface current of fresh water flowing towards the Mediterranean Sea, in addition to NE winds[4a]. Inside the Black Sea, currents flow counter-clockwise and favour a trip to the east along the Turkish coast, before crossing over to Crimea against prevailing winds. Nevertheless, ancient seafarers are known to have sailed massively along the western Black Sea coast to Crimea and to the Azov Sea, possibly because this trip was free of pirates.
The need for a large number of shelters follows from the fact that sailors may need to wait for proper wind conditions or may try to escape bad weather conditions. Even though they can sail 50 to 100 nautical miles in a day (see Ancient Measures), it is important to know where they can find a safe shelter within two to three hours of navigation, i.e. only approx. 10 miles.
It has hopefully been made clear in this (very) brief survey of Mediterranean sailing that it is a vast and complicated subject that requires a lot of experience. History shows that Mycenaeans (ca. 1500-1200 BC), Phoenicians (ca 1200-150 BC) and Greeks (ca. 800-300 BC) were very good at that. Mycenaean sailors had a very difficult playground in the Aegean Sea. Perhaps their experience was later taken over by Phoenicians who used it to travel all over the Mediterranean Sea and beyond.
Modelling Mediterranean sailing routes
Our aim in this section is to compute travel times between various ancient ports (hubs discussed in the section on “Ancient maritime trade”) and to compare different alternative routes between two ports, e.g. Alexandria and Portus, compare both ways to and from each place, and compare seasonal influences.
Ancient sea routes have been described by several ancient authors such as Strabo and Pliny, and by an anonymous author who wrote a document known as the “Stadiasmus”. Pascal Arnaud produced a monumental work in 2005 summarising these ancient navigation routes. Apart from a collection of 127 Mediterranean navigation routes, he was able to define the main units of distance. This is not as trivial as it would appear at first sight, as each distance at sea was defined by sailing days and was converted by the ancient scholars into distances in stadia. Pascal Arnaud was able to distinguish the following basic units of distance: 1000 stadia, 700, 600 and 500 stadia. He was able to correlate these distances with travel times as follows:
- one-day + one-night sailing (24 h) yields a 1000 stades travelled distance,
- half a day & night (12 h) yields 500 stades,
- one daylight sailing, “daytime” (15-17 h) yields 600-700 stades.
With one stadium equalling 1/10th of a nautical mile, the average ship velocity therefore was around 4 nautical miles per hour, i.e. 4 knots. It may be argued that this definition of distances based on travel times depends on the meteorological conditions (winds and waves, assuming that currents are usually negligible in the Med). This is true, but ancient sailors had no accurate instrumentation for measuring positions expressed in latitudes and longitudes. Ancient authors reporting distances at sea obviously took the meteorological conditions of each trip into account and provided some kind of averaged value. We may thus consider at this point that we have a reliable data set for distances between ports reported by ancient authors. This data set was carefully analysed and validated by Pascal Arnaud.
Let’s now turn to a computational model of these Mediterranean navigation routes. A major attempt was conducted in the ORBIS Project by Stanford University (http://orbis.stanford.edu/# ) in 2011-2014. This model is a superb tool that seems to be still operational online, but:
- it works with a coarse 5 x 5° grid for wind stats,
- the choice of the “fastest” track is not explained (black box effect),
- it is “relying on a modest number of segmented routes” and “roughly approximates the preferred routes of sailors in the Roman period” and it is therefore not open to choosing other routes.
Based on the ORBIS approach, I decided to build my own model based on a 1 x 1° grid for wind stats, and allowing any route to be chosen on that grid. This approach is clearly using averaged values for winds (based on long term statistics) and averaged values of ship speeds for each relative wind direction, including parameters such as high waves and low visibility. Hence, computed travel times are also averaged values.
In a first stage, the detailed MedAtlas data was taken over for each point on a 1 x 1° grid for the whole area of the eastern and central Mediterranean Sea, say from Tyre to Portus. This encompasses 147 grid points with wind data for annual and four seasonal conditions.
Secondly, the ship model was taken over from Arcenas. This ship model is a ship-speed rose providing a ‘Velocity made good’ (Vmg) for each relative wind direction. Vmg is the resulting velocity of the ship in the desired direction, which may result from various sailing techniques such as tacking and gybing, including the ship’s leeway.
Third, the wind statistics were combined with the ship model to provide resulting ship speeds for each heading at each grid point.
Fourth, this result is used in a navigation model, where a track passing through a number of grid points is chosen from one place to another (e.g. harbour or promontory). The distance between each point is computed by means of spherical trigonometry and the travel time is deduced from the ship speeds at each grid point.
In order to validate this ‘MedNav’ model, around 40 trips which had been identified by Pascal Arnaud were used. The result is shown below in a comparison of computed travel times with travel times reported in ancient texts.
The red dotted line is the line of perfect agreement when computed and reported travel times are exactly equal. Both grey dotted lines show +30% and -30% values and it can be seen that most of the points lay within the +/-30% range (that is nearly a factor one in two). It may be noted here that this range corresponds to the meteorological uncertainties you might take into account when planning any trip at sea with a sailing boat.
Globally, the data points show a nice agreement with a correlation coefficient of 0.91. This result also shows that the Arcenas ship is quite good.
A distinction was made between trips with favourable winds and trips with adverse winds (e.g. travelling from east to west in the eastern Med or from south to north in the Aegean). This result shows that little impact of wind conditions is felt and proves that ancient authors have taken this cleverly into account in their distance estimates.
We are now ready to go one step further in using the MedNav model for computing the famous Alexandria-Portus routes, including seasonal effects.
The route from Portus to Alexandria enjoys favourable NW winds all along. From Portus, we sail down to the strait of Messina (ancient Zankle) and from there to Alexandria in a direct SE track (green arrowed line in figure above). This trip reputedly takes one to two weeks. This direct track, as the crow flies, is 1084 nautical miles (2007 km) and is sailed at an average speed of 4.5 knots in 244 sailing hours (ca. 10 days). Taking the same way back would mean beating the adverse wind all the way and it would be very uncomfortable. We have therefore been looking for other routes:
- Alexandria-Rhodos-Kythera-Zankle-Portus, the north route via the southern Aegean and Ionian seas.
- Alexandria-Phycus-Leptis Magna-Zankle-Portus, the south route via Cyrenaica.
- Alexandria-Paphos-Rhodos-Kythera-Zankle-Portus, via Cyprus.
- Alexandria-Rhodos-Kythera-Phycus-Leptis Magna-Zankle-Portus, a combined route.
The computations show that the fastest route is the north route via Rhodos, with 452 sailing hours (2.8 kt average speed). The next fastest is the uncomfortable direct track beating the wind, with 462 hr. The south route requires beating the wind between Alexandria and Phycus (Cyrenaica) and yields 476 hr. Another route leads to Rhodos via Paphos (Cyprus), but is slower with 482 hr. The combined route via Rhodos, Kythera and Phycus is the longest in distance and in time, with 490 hr. Summarising, it may be stated that the trip from Alexandria to Portus takes 450 to 500 sailing hours depending on the chosen route. That is around 20 sailing days, plus or minus one day, and twice the time required to sail with favourable winds from Portus to Alexandria.
It seems that these results nicely fit the general feeling of scholars interested in this subject, and we now have a less subjective base for this feeling.
With this renewed trust in our model, we can investigate further and check the seasonal influence. Let’s take the same trip between Alexandria and Portus, both ways, and compute the travel times in each of the four seasons.
|Portus > Alex direct track||266||244||267||253|
|Alex > Rhodos > Portus||402||452||381||360|
|Alex > Leptis Magna > Portus||440||490||420||435|
On the way to Alexandria, seasons do not matter much as the travel time is around 240-270 hours (10-11 days). However, on the way to Portus, seasons do matter a lot. Summer is obviously the worst period to sail in this direction, as the trips in fall and winter are clearly faster. Note that the south route via Leptis Magna is always somewhat slower than the north route via Rhodos, but this does not prevent you from doing so if you have some lucrative business there.
It must have been quite a temptation to sail in winter time (during “mare clausum”), but the risk of an unexpected storm was much higher (see Luke’s final trip to Rome, Luke’s Acts, 27, 11).
Another recurring question is what is the fastest route from Alexandria to Rhodes in summer, with north-western etesian winds. The direct route from Alexandria to Rhodes is around 350 nautical miles; the next shortest is via Paphos (Cyprus), with 500 n. miles; the next is via Tyre (Lebanon) and Paphos with 750 n. miles and the longest is via Tyre, Seleucia Pieria and along the southern Turkish coast, with 800 n. miles. The travel times are respesctively 120 h, 150 h, 225 h and 230 h. The direct route is fastest but requires quite some struggle with the wind at close reach. The trip via Paphos will be fast to Paphos and rough after that. Both trips along the Levantine coast are much longer and are justified only if particular business can be done there during the trip.
We may thus confirm that two return trips between Alexandria and Portus could be undertaken each year as follows:
- Alexandria to Portus in spring, just after the Egyptian harvest, arriving in Portus in May-June (note the ‘Alexandrian ships’ were overwintering in Alexandria in order to be ready for departure in spring as soon as harvesting was conducted),
- Portus to Alexandria in summer, arriving in Alexandria in July-August,
- Alexandria to Portus in fall, arriving in Portus in September-October,
- Portus to Alexandria in fall, arriving in Alexandria by the end of October.
Red Sea versus Nile sailing
Much discussion has taken place concerning the route when sailing back from the Indian coast, the Somalian and the Yemenite coasts. The southern part of the Red Sea is subject to reversing monsoon winds and sailors could make use of that. However, north of 20° of latitude, the northern winds blow all year round on the Red Sea, making the trip back to the north quite uneasy. Some merchants therefore had their ships calling at ports like Berenike (near Ras Banas) and Myos Hormos (Quseir al-Qadim) in order to continue the journey by land via Coptos (Qift) and the Nile down to Memphis (Cairo) and Alexandria. Other merchants decided to call at ports on the Arabian side (e.g., Sharm al-Wajh in Saudi Arabia, acc. to Fiema, 2020) and further by land to Petra and Gaza. These routes were an alternative to sailing to Clysma (Suez) with continuous northerlies, or to Charax Spasinou (Jebel Khayabir, about 50 km north of Basra), via the Gulf, in order to reach the Mediterranean coast near Palmyra, but with lots of NW winds also.
Cooper (2011)  shows that both routes had pros and cons. The journey time from Berenike to Memphis was quite similar for both routes (at best around 3-4 weeks). Both routes induced a number of risks (grounding at sea and on the Nile, pirates at sea and on land, etc.). Sidebotham (1989) suggested that bulky agricultural cargoes might have travelled through Clysma, while more luxury cargoes might have taken the land route and the Nile.
The final answer may not yet be given but the sketch below will provide a summary of the physical conditions and approximate journey times.
Physical conditions concern current and wind. Schematically, the current in the Nile varies between 1 knot (ca. 2 km/h) in the low water season (December to June) and 3 knots (ca. 6 km/h) at the peak of the flood season (September). The wind is blowing from north, against the current, most of the time in the Nile valley (note that the Nile delta is subject to seasonal variations with its famous summer northerlies). The Red Sea is subjected to a similar wind regime in its northern part (say north of Port Sudan at 20° latitude) and the Red Sea Pilot states that “you should not count on any south winds from Ras Banas northwards” (at 24° latitude). The southern Red Sea has seasonal variations due to the monsoon regime and winds can be strong in the Straits of Bab el-Mandeb.
Journey times for shipping are shown northbound and southbound. These are of course approximate times without stops at ports. Southbound on the Red Sea is pretty fast with around 50 to 80 nautical miles per day (i.e. 4 to 6.5 knots assuming 12 hours/day sailing time). Northbound on the Red Sea is very slow as sailing is not possible in a straight line and no more than 20 to 25 nautical miles/day can be done (i.e. less than 2 knots assuming 12 hours/day sailing time). These values are confirmed by Pascal Arnaud (2005) who is a Roman historian and a sailor himself .
Journey times on land between the Red Sea ports and the Nile are provided also.
As a result, the journey time from Berenike to Memphis was ca 3.5 weeks by the Red Sea and ca 4 weeks by the Nile …
A small difference that may not have been
that important in ancient times
when “time is money” was less important than
“have a safe trip back home” …
 ARNAUD, P., 2005, “Les routes de la navigation antique”, éd. Errance.
ARNAUD, P., 2014, “Marseille grecque et les routes du commerce maritime”, in “Les territoires de Marseille antique”, Arles, Paris, éd. Errance, p 185-213.
TAMMUZ, O., 2005, “Mare clausum? Sailing Seasons in the Mediterranean in Early Antiquity”, Mediterranean Historical Review, Vol 20, No. 2, December 2005, pp. 145-162.
 MORRISON, J.S.; COATES, J.F.; RANKOV, N.B., 2000, “The Athenian Trireme”, Cambridge University Press.
See also: http://kyrenia-collection.org/styled-4/styled-7/index.html
 Sea breezes blow from sea to shore in the afternoon, easing the arrival to harbours. Land breezes blow during the night and early morning easing departure from the harbour.
Acc. to Rod Heikell in “The Adlard Coles Book of Mediterranean Cruising”, 2012, Chap 6, p 312-313:
“1. The relatively high temperatures of the Mediterranean mean that sea breezes are not the gentle zephyrs encountered in more temperate climes. In many places, the temperature differences generate winds up to Force 5–6 and can reach up to 50 miles off the coast.
2. There is a fairly accurate wind clock for the sea breeze. As the land warms up in the morning the sea breeze will begin to blow at 1100–1200 local time at around Force 2–3. Usually within an hour the wind will get up to Force 4–6 and will blow through the afternoon until early evening. The wind will die off fairly quickly around 1900–2000 local time. The abruptness of the change is linked to the air temperatures and geography of a region. In general, the higher the temperature, the more abrupt the transition between morning calm and the onset of the full force of the sea breeze. The terrain affects the sea breeze according to altitude: low-lying plains or gentle S-facing slopes will heat up more quickly than mountain ranges with valleys in shadow for much of the day and so generate greater pressure differences and stronger winds.
3. The direction the coast faces will affect the sea breeze clock. In general S-facing coasts will have an earlier sea breeze than N-facing coasts. Likewise, E-facing coasts will have an earlier sea breeze than W-facing coasts.”
It may be added here that coastal effects modify the wind direction and strength, e.g. around a headland with high land where the wind will follow the shore and curve around the headland with an increased speed.
[3a] Lucian of Samosata (2nd c. AD) tells the fascinating story of a very large grain freighter caught in a storm off Cyprus:
“I had it from the master, a nice intelligent fellow to talk to. They set sail with a moderate wind from Pharos, and sighted Acamas on the seventh day. Then a west wind got up, and they were carried as far east as Sidon. On their way thence, they came in for a heavy gale, and the tenth day brought them through the Straits to the Chelidon Isles; and there they very nearly went to the bottom. I have sailed past the Chelidons myself, and I know the sort of seas you get there, especially if the wind is SW.
It is just there, of course, that the division takes place between the Lycian and Pamphylian waters; and the surge caused by the numerous currents gets broken at the headland, whose rocks have been sharpened by the action of the water till they are like razors; the result is a stupendous crash of waters, the waves often rising to the very top of the crags.
This was the kind of thing they found themselves in for, according to the master, and on a pitch-dark night! However, the Gods were moved by their distress, and showed them a fire that enabled them to identify the Lycian coast; and a bright star–either Castor or Pollux–appeared at the masthead, and guided the ship into the open sea on their left; just in time, for she was making straight for the cliff. Having once lost their proper course, they sailed on through the Aegean, bearing up against the Etesian winds, until they came to anchor in Piraeus yesterday, being the seventieth day of the voyage; you see how far they had been carried out of their way; whereas if they had taken Crete on their right, they would have doubled Malea, and been at Rome by this time.”
[4a] CASTELLI, T., 2019, “Entrer et sortir du Pont-Euxin durant l’Antiquité”, Advances in Ancient Black Sea Studies: Historiography, Archaeology and Religion, Editura Mega, Constanza, (26 p).
 Acc. to Rod Heikell in “The Adlard Coles Book of Mediterranean Cruising”, 2012, Chap 6, p 313: “From the Dardanelles it blows from the NE, curving down through the Aegean to blow from the N and NW before curving to blow from the W around Rhodes.”
 COOPER, J.P., 2011, “No easy option: Nile versus Red Sea in ancient and medieval north-south navigation”. In W.V. Harris & K. Iara (eds), Maritime Technology in the Ancient Economy: Ship Design and Navigation. Journal of Roman Archaeology Supplementary Series 84: 189–210.
This paper cites SIDEBOTHAM, S.E., 1989, “Ports of the Red Sea and the Arabia-India Trade”, in Fahd, T. (ed.), “L’Arabie préislamique et son environment historique et culturel”, (Strasbourg, 1989), (p 195–223).
 HEIKELL, R., 2015, “Sailing Ancient Seas”, Taniwha Press, UK.
 WHITEWRIGHT, J., 2011, “The Potential Performance of Ancient Mediterranean Sailing Rigs”, The International Journal of Nautical Archaeology (2011), 40.1: 2–17.
See also his 2008 PhD thesis at Southampton University.
 VIRGIL (Eneid, 5, 8-25) explains what any sailor would still do today with unfavourable winds, i.e. try tacking, but bear away to downwind if the wind is too strong.
 ARISTOTLE (Mechanica, 851-b) already pointed this out, see POMEY, P., 1997, “La Navigation dans l’Antiquité”, p 80-82.
 ARNAUD, P., 2005, “Les routes de la navigation antique”, edt. Errance, (248 p) & ARNAUD, P., 2012, “La mer, vecteur des mobilités grecques”, in “Mobilités grecques”, Capdetrey & Zurbach (edt.), Scripta Antiqua 46,Ausonius, Bordeaux, (p 89-135).
Note that Pascal Arnaud not only is a famous professor in Roman History, but also an experienced sailor who has been sailing the Med himself for decades.
 One Roman stadium is 185 m long, which equals 1/10th of a modern nautical mile of 1852 m. However, ancient authors often used other definitions of the stadium (Greek, Egyptian, etc. which are somewhat different (say from 150 to 200 m).
 WHITEWRIGHT, J., 2011, “The Potential Performance of Ancient Mediterranean Sailing Rigs”, The International Journal of Nautical Archaeology (2011), 40.1: 2–17. According to ancient reports, ancient ships sailed at 1 to 2 knots in adverse wind conditions and 4 to 6 knots with favourable winds.
 MEDATLAS, 2004, “Wind and Wave Atlas of the Mediterranean Sea”, Scientific Report RTP10.10, Western European Armaments Organisation.
 ARCENAS, S., 2015, “ORBIS and the Sea: a model for maritime transportation under the Roman Empire”, ORBIS Project, Stanford Univ., (6 p), (http://orbis.stanford.edu/# ). We chose his “fast ship”.