Much has already been written, by us and others, about the UC Davis West Village project’s connection to the sun – from the photovoltaic panels that provide the power to make it the nation’s largest zero-net energy community, to the façade specific shading devices and exterior cladding systems that help to regulate heat gain from the Central Valley’s abundant summer rays. The same sensitivity to specificity and place that are embodied in these elements extend to other details of the project that have slipped under the radar – such as the Village Square’s Icon Tower Sundial.
History & Type
Sundials have marked the passage of time for thousands of years, and in seemingly just as many forms – running the gamut from poles stuck in the ground or ancient Obelisks that provide a reading of time via the length and direction of a shadow cast on the ground, whose location varies with the seasonally-changing altitude of the sun (thus referred to as altitude dials), to more complex, elaborate, and accurate devices in medieval and Renaissance times, – such as the Regiomontanus Dial – that relied on knowledge of the angle of the Earth’s axis and the cardinal directions (thus referred to as direction dials) to provide more accurate and consistent readings of time, and back again to a simple piece of die-cut card stock in a box of Cracker Jacks. The Village Square’s Icon Tower Sundial is a form of altitude dial, (specifically, a nodus-based vertical reclining-declining sundial) and falls somewhere in between these two extremes in terms of its complexity.
Though the means and expression of these sundials are myriad, they all share two basic elements: the gnomon and the dial. The gnomon casts a shadow that indicates the passage of time on the dial – the plane on which the passage of time is marked. The Icon Tower Sundial’s gnomon is nodus-based – it indicates time by following the path of the tip of the gnomon, or a single point of light within the shadow of the gnomon. Altitude dials of the Icon Tower’s type will typically be marked with lines for the time of day sweeping down across three lines running side-to-side across the plane of the dial that indicate the season:
- Winter Solstice Line: The short, curved line closest to the gnomon indicates the path of the tip of the gnomon’s shadow on the winter solstice, around December 21.
- Equinox Line: The sun’s shadow follows the vernal and autumnal equinox line on March 21 and September 22.
- Summer Solstice Line: The long, curved line farthest from the gnomon indicates the path of the tip of the shadow on the summer solstice, around June 21.
On the Icon Tower’s Dial, each season line is punctuated at the intersection with the time lines with a 2″ hole.
How the Sundial Works
As the sun moves daily from east to west, the gnomon’s shadow follows a path from left to right. The position of the shadow on the dial indicates the hour of day. The sundial tells “solar time” or “local apparent time”, which differs slightly from “clock time” because of the displacement of Davis from the standard meridian for the Pacific Time zone (at 120 degrees W), the irregular annual motion of the Sun, and the annual observance of Daylight Savings Time. Between the months of April and October, one hour must be added to the time shown for an accurate reading of daylight savings time. The daily paths vary throughout the year – In summer the sun is higher in the sky and thus the gnomon’s shadow falls lower and longer on the sundial, while in winter the sun is lower and the shadow falls higher and shorter on the dial.
Design in Revit/BIM
If the gnomon and the dial are properly oriented to the cardinal directions of the compass and the axis of the Earth’s rotation, and one is armed with the local geographical latitude and a proficiency in trigonometry, these lines and points can be determined mathematically and plotted on a graph. In the case of the Icon Tower Sundial, however, the rotation of the tower structure itself relative to true north, when combined with the receding curvature of the supporting steel and a graphing calculator that hasn’t seen regular use since graduate school, made any such attempts at applied astronomy a daunting task to say the least. As the project was modeled in Revit, we were fortunate enough to have more powerful tools at our disposal than my old TI-85.
Through a series of solar studies keyed to position of Davis on the globe, we were able to accurately chart the course of the gnomon in one-hour increments to plot and trace its path at key times of day throughout the year. The resulting piece is thus not just Sundial, but a site-specific, one-of-a-kind representation of the passage of time in this place.