Important structures for constructing and using the bearing-dial.
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When analyzing the bearing-dial we have to split into two phases: "Constructing and using the dial".
Constructing the bearing-dial.
The bearing-dial is made for 61'th latitude North (Greenland) and a declination around 19 (summer).
The edge of the inner circle of the bearing-dial is a gnomon = 6,9 mm (the height of the edge) throwing a shadow.
You can use the applet above making your own experiments with gnomoncurves and you can find more accurate analyses elsewhere on the site.
|The bearing-dial is constructed for latitude 61North and a declination = 19 (around summersolstice).|
|Marks for equinox.|
Marks for wintersolstice around 48N.
Check the marks here.
Using the bearing-dial:
The "user" functions are: "Bearing the sun, showing points of compass and latitudes for land to explore". Click here seeing my experiments with a true model of the bearing-dial placed in the sun.
Of course the Norse could have used the bearing dial for navigational purposes, and I think they did when finding the four points of the compass, and the azimuth during the day - but I don't think that's the main purpose - because the bearing-dial is extremely sensitive for an exact horizontal state and I'm sure it is used mostly for stationary measurement.
You have to organise your society with some sort of a calendar and use some vital points of the day (the Norse called them "eykts" or daymarks), and that was a purpose as well.