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Ptolemy's Geography refers to a place written in Latin as ALATA CASTRA or in Greek as πτερωτὸν στρατόπεδον (pteroton stratopedon, Ptol. 2.3.13). Ptolemy's map gives the latitude and longitude of the site. Ptolemy's map shows the whole of Scotland as very distorted, however most authorities would locate these coordinates somewhere in NE Scotland.

Etymology

The etymology, in both the original Greek and Latin forms, means "Winged Camp" or "Camp of the Wings" (or perhaps "Camp of the Feathers"). Alata comes from the same root as the Roman name of the cavalry or ala which were usually placed on the wings of the army. Castra is a term that was applied to temporary camps, which is not the same as the similar Latin word (castrum) used for forts.

Importance

The site is important because it was selected as one of the six British sites listed by Ptolemy in the introduction to his Geography together with their longest length of day. The length of day can be used to calculate the latitude. These "benchmark" sites would be the locations whose position was most accurately known and so used to determine the relative position of other sites. As can be seen, they are fairly evenly spaced at half degree intervals up the length of Britain.

Latin Modern location Length of day Ptolemy latitude
Vectus Isle of White? 16.7 52 2/6
Londinium London 17.0 54
Eboracum York 17.5 57 1/3
Caturactonium Scottish borders 18.0 58
Alata Castra NE Scotland 18.5 59 1/3
Dumna Near Orkney 19.2 61 1/3

So, unlike other sites these six have their latitude given in two different ways which reduces the likelihood of transcription errors. Moreover Ptolemy would have been careful to pick the sites for which he had the best information. However there are still large errors and Vectis (Isle of White?) would appear to be on the other side of the English Channel. If however we use the known locations of London and York as our starting point, then we assume the northermost location Dumna must be on an island in or near Orkney (it is too far north to be on anything but the tip of mainland Scotland), we find Alata Castra must be around the latitude of Aberdeen (and Caturactonium somewhere in the Scottish borders).

Pinnata Castra

A controversy has arisen about the name of Alata Castra. This arises because it is listed by Ptolemy as being between the unidentified towns Tamia & Tuesis and in the Ravenna Cosmology (R&C#211) there is another name Pinnatis listed between another two unknown entries, Iberran & Tuessis. Tuessis is readily identified as the similar entry in Ptolemy and as pinna (or penna) is Latin for 'feather' or 'winged' Pinnatis it may be translated as having a similar meaning to Alata. Thus it has been suggested that the two names are two different Latin translations of the the same original British (or perhaps Greek) place name. On this basis many now suppose the original name was Pinnata Castra although this name is not found in any classical texts.

Potential sites

Various sites have been suggested as the location for Alata Castra but as the nearby name of Tuesis is also listed by Ptolemy as a river, which is likely the Spey or Deveron, Alata Castra must be located somewhere in the NE of Scotland. Before recent excavations suggested a later period of occupation, one oft suggested candidate was Burghead Fort, Moray. But as yet no convincing evidence has been presented to link Alata Castra to any site whether Roman or British.

Identification as Inchtuthil (Unlikely)

However, just as the name as been controversial, so the location has also led to speculation. Some argue that because Ptolemy highlights Alata Castra together with two other principle towns (London & York) that therefore Alata Castra must also be an important site such as a Legionary Fortress. As there is only one suitable Legionary Fortress even remotely far enough north to be considered, Inchtuthil Legionary Fortress is then equated as "Pinnata Castra".

This identification is unlikely: Inchtuthil is too far south and unlike other sites a simple transcription error does not easily explain this discrepancy; Inchtuthil is on the banks of the Tay which is usually accepted to be Ptolemy's River Tina and not the Tuesis as would be required, and the fortress was not as important as suggested as unlike London or York it appears to have been abandonned before completion.

Linguistically however, the name Pinnata Castra does not work with Inchtuthil: the required link between Alata Castra and Pinnatis is their "closeness" to a river 80 miles north; it requires the Roman fort to have a non-Latin name which was then arbitrarily translated in two different ways, and to justify moving the location ~80miles south to Inchtuthil, the argument used is that 'Pinnata Castra' must be a key Legionary fortress, but castra means the location would be a camp and not a fortress.

See: Dictionary of Greek and Roman Geography -Alata Castra, by William Smith, LLD, (1854);
A Latin Dictionary - penna, by Charlton T. Lewis, Charles Short;