Antarctic observations and fixes

What you are looking at

Dated positions: farthest souths, the contested sightings of 1820 and 1840, the nineteenth-century landfalls, and the Endurance sequence from besetment to South Georgia.

How to read this layer

Circle size is confidence, not importance. A large circle means the record is well established. Nothing here is large.

The evidence class matters more than the position. Several 1820 and 1840 records are filed as reported rather than observed, and that is not a doubt about whether the ships were where they said they were. It is a statement that what was seen, and whether it counts as a sighting of the mainland rather than of an ice front, is a question the historiography has not settled. The data model refuses to settle it by choosing a field.

Some records are dated to the month rather than the day. That is also deliberate: the exact days of the January 1840 sightings are part of the dispute between the American and French expeditions, and pinning them here would resolve that dispute in a spreadsheet.

Historical scope

1774 to 1916.

Sources and evidence

Each position names the source it should be read from. Most are recorded from the general literature with the locator still pending, which is why they have not left the raw state.

The James Caird passage is the exception, and it is the shape the rest should eventually take. Its nineteen noon positions were read out of the published transcription of Worsley’s navigational log (Bergman, Huxtable, Morris and Stuart, Records of the Canterbury Museum 32: 23-66, 2018), each carrying the class the log itself gives it: observed with an instrument, or reckoned from course, speed and time. On the five days that have both, both are kept as separate records, because the distance between them is the evidence - on 26 April 1916 it is seventy-eight nautical miles. Those rows are at normalized: read against the source, not yet reviewed by a person.

Reconstruction and uncertainty

No uncertainty envelope is drawn, because none has been established.

The Endurance sinking position deserves particular care. The figure is a calculated result: an observation, an instrument, an assumption and an arithmetic, each with its own error. It has been recomputed from Worsley’s logbook in the navigation literature, and that recomputation is the source it should be cited from. Presenting the coordinate as a simple fact would undo the argument the record exists to make.

Editorial decisions

Positions are stored at the precision the literature reports and no further. The build rounds coordinates only to keep its own bytes stable, and that rounding is not a claim about accuracy.

Data fields

evidenceClass, geometryProvenance, confidence, reviewState and act. See the Antarctic data fields.

Data and downloads

CC BY 4.0 for the compiled records. In review: not citable as established evidence.