Frederick W. Sawyer, president of the NASS (North American Sundial society), developed a new type of sundial in 2005.
Fred discovered several new types of sundials in the past, but we would like to show an example of this latest development.
The basis of the new sundial is a map projection developed in Germany around 1914, and in the United Kingdom around 1922.
The azimuth of the sun plays a large role here, and thus the newly developed sundials are based on sun azimuth measurement.
Several possibilities for new sundials were proven and published. Here, we shall discuss a polar sundial.
The figure above shows an ordinary polar sundial.
The dial face is meant for 52 degrees North, but could be used on other latitudes.
It is parallel to the pole style and aimed towards the south.
The hour lines, here for apparent time, are parallel to each other.
A pin-gnomon, with a height equal to the red line, is square to the dial in the middle of the XII-hour line.
The shadow of the gnomon terminus is the readout in this sundial.
As well as time, the date can be read. Seven date lines, according to the signs of the zodiac are on this sundial, but other date lines are equally possible.
Up to this point, there is nothing new under the sun.
The second figure, below, shows another polar sundial, but one looking nevertheless completely different. Again, there are date lines according to the zodiac, but they look slightly different.
Of greater importance is the position of the hour lines. They all go through the same point, and meet at angles of 15 degrees.
In the centre there is again a pin-gnomon, square to the dial, but of greater but otherwise unspecified length. This sundial must be read differently.
The date cannot be read; on the contrary, in order to read time, the date must be known.
The time is read where the shadow of the long gnomon intersects the appropriate date line.
As stated earlier, the sundial shown here is just one example of the many possibilities that this development offers. The art of gnomonics is still full of surprises, and its possibilities will not have been exhausted for a long time.
Fer de Vries
Source: Compendium, bulletin of the NASS, vol. 12, nr 1, March 2005
Article by F.W. Sawyer: Compressed Gnomonic Sundials
The necessary math is incorporated in an appendix.