How the ancients navigated

[Byrd]

 I think the Great Pyramid was the major marker not quite at the 23.5 parallel but near enough it might even have had been the summer solstice marker when it was constructed for the purpose of this example.
 The technique is simple enough, and rests on the fact that the suns ground position changes by about a degree each day which is sixty nautical miles. The Sun at the solstices reaches 23.5 degrees north in the northern hemisphere and the same in the southern hemisphere at roughly the tropic of Capricorn. This method requires a static marker like the known position of the GP or in modern times a place on the map or chart. I will give a practical example.
 Say I am in the Western Pacific Ocean on the day of the summer solstice, I know that the suns ground position for that day tracks the 23.5 degrees south line of latitude. Thats as far south as the sun goes south. I look on the Chart and notice that if the suns ground position went down to Sydney. Then it would be... off the top of my head about fifteen days sun distances from Sydney to the 23.5 line of lattitude. I draw a line on the chart from Sydney up to the 23.5 lattitude line,and wait for the sunset that day,In modern times I go out on deck and as the last glimmer of the setting sun shines over the horizon I take a compass bearing of it, Knowing that Sydney is fifteen sun positins south of it , the compass will read approximately fifteen degrees less, so I note the two compass results, and draw the lines on my chart and triangulate my position on the ocean. In Ancient times a hinged stick would do the same thing. Not as precise as present day GPS but with a skillful operator a feasible way to draw a map or chart Islands, without an accurate chronometer.

Firstly, the Great Pyramid isn't visible at a range of three miles (too small, and at 3 miles the curvature of the earth comes into play.)

Second, why use the GP at all?  You could use a coastal mountain (volcano) that you might be able to see for 4 or 5 miles... and that's inefficient because measuring distance on the water isn't as easy as it is measuring it on land.  The big Tahitian canoes travel at a rate of about 3-6 miles per hour (depending on the wind), and it's very hard to tell the shift in the sun's position if you've only traveled 20-30 miles.

[annonentity]

Because it could be used as the primary latitude marker ,in a known place from which all other reference points could be compared to .If you were in the western ocean, you would use dawn, to get an angle. This would act as the Sydney in my example. Once you have the angle of the sunrise or sunset. It would remain essentially the same for all practical purposes, if the Earth was flat the angle would change as the suns subpolar point would cause it to contract as it moved. as it moved further away from you...but as the Earth is a Sphere it would essentially be the same as it moved over the straight northern point in the line up from Sydney. on the 23.5 meridian. Since you know the distance from Sydney to the tropic of capricorn line for that day, you have a distance and two fixed points to do a triangulation. In those days they were mapping and charting and fixed known points would be  scarce.
 So to use an analogy, it is like having a laser light shooting vertically up into space from the two locations,and since they are known positions you can triangulate between then to get another known fixed point. As sixty nautical miles is one degree on the earths surface,You know the degrees from the sunset point to Sydney or the GP ..or the whatever.