Early Navigation Practices

The End Of The Dark Ages - Mathematics And Astronomy - and A New Way Of Thinking About Navigation

During the Dark Ages, those five centuries that followed the destruction of the Roman Empire, only very limited, if any, information is available about the navigation techniques of the time. It is presumed that sailors relied on their powers of observation and sea-crafts. Their skills are exemplified by great navigational feats by Vikings and Irish.

After A.D. 1000 Europeans began taking an interest in mathematics and astronomy which they found to be accomplishments of the Arabs whom they were taking over by conquest. The European Church was suspicious of the new knowledge and instruments, but interest and advances continued.

One of the scientific instruments that the conquering Europeans were eventually to develop as a direct result of their conquests and exposure to new learning was the Sea Astrolabe. Developed about 1470 the Sea Astrolabe was based on the design of the much earlier planispheric astrolabe, which had its origins with the Greek philosophers and astronomers immediately prior to the European conquest which had ended the Dark Ages. The Sea Astrolabe was used to plot the attitude of the sun near the meridian. It came into use on ships - the Spanish Armada (1588) carried it (Turner, 1980:31).

The Creation Of Maritime Charts

Charts and maps were invented to record and transmit information about position and phenomena on the surface of the earth, that is, a sphere. Making the chart itself in the form of a sphere, in order to avoid the problems of projecting onto a flat sheet, was a quite early development, but the major development came with the flat type. Plotemy's maps and globes from the second century AD were the best-known maps for many centuries.

The oldest specifically maritime chart (Carta Pisana) is dated at 1275; it covers from southern England to the Black Sea. This indicates current commerical activity. It probably showed magnetic directions, and had the compass roses which characterised the "portolan maps". These were progressively corrected and refined. Rhumb lines appeared, but had yet to be linked to meridians of longitude - with which they make constant angle - which had thenselves still to be invented. However, the maps did not show scale or direction as we expect a map to do: "Relative size was according to relative importance, or relative knowledge: relative position to a general notion of the four quarters of the world." (Taylor, 1956:111). The increase in knowledge generally, and especially in exploration and commerce, in the late 1400s, 1500s and 1600s allowed maps to be progressively improved.

Maps could be diagrammatic only in east-west directions until longitude could be accurately determined. The first methods that were found could be used on land, but they were too awkward for maritime determinations, so maritime charts lagged land-maps: the Dutch East India-men could still find New Holland looming unexpectedly to the east as they made for the Spice Islands in the 1600s. Tasman completed the Dutch mapping of New Holland from Cape York westward, south and east to Tasmania in an attempt to safeguard the Dutch maritime traffic. However longitude remained elusive.

The effect through the centuries of the continuing ignorance of longitude is exemplified by the map created by Doncker which illustrates Tasmania too far to the west.