It is already approximately five years old, but I only saw the sundial in October 2004.
A shadow plane sundial in Tiel.
Thirteen stone slabs are in the shadow planes of the sun. The edges are marked with numerals 9 through 21 for summer time readout.
On each whole hour, the corresponding slab has its shadow fall in its own plane. Neither of its sides catches any sun.
For times between whole hours, we look for the pair of slabs of which one has its shadow to the left, the other to the right.
A bit of interpolation will let us read the time reasonably well. We must apply the equation of time to get clock time.
The slabs are fixed in a concrete ledge, cast invisibly under the surface.
On either side of it, the hour slabs slope in opposite directions.
The next photograph shows this well.
