Zaragoza Multi-Box Solar Clock

The dial is delineated in minutes with over 3000 markings on the scale.

The information panel is a stainless steel sphere with instructions and an Equation of Time adjustment table.

This huge sundial in the Parque de Oriente in Zaragoza, Spain, was the Guiness Book of Records "World's Largest Sundial" when it was first erected. The gnomon is over 46m long and 30m high.

Antonio describes the project:

"The challenge was immense. The soil is of a very bad quality in geotechnical terms and the torque that the gnomon exerts over it is huge.

I designed the gnomon without structure; the plates withstand all the structural stresses, but that adds a lot of complexity to the structural analysis because other phenomena come into the equation like the stability of those plates under heavy and combined stresses-shears-compressions. 

Initially the gnomon was composed of three pieces, bolted together but eventually, after inspecting very carefully every single meter, turn and lamp post along the 250 km trip from the workshop to the site, I decided to build it from a single peace and to transport it as such.

The gnomon is so slender that is prone to resonance (like the Millennium Bridge in London).

There are hundreds of design provisions to deal with corrosion, serviceability, public lighting, lightning strikes, grounding, etc.

When the gnomon is thermally stable (cold months and some hours of the day), the accuracy is very high, less than 20 seconds of error for most of the tests."