Images and text copyright by David Le Conte
(except as marked)
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Thousands of years ago Neolithic man erected stone monuments on
These prehistoric monoliths were
the inspiration for
The obelisk is made up of 50 layers of Guernsey granite - one layer for each year of freedom. The top layers are sheared away to represent the five years of occupation endured by islanders. The seating and platform are off-white French granite which enhances the visibility of the shadow cast by the obelisk.
Inscriptions placed on the seating record the major events of the 9th May 1945: the signing of the surrender of the German forces at 7.15 am, the landing of the British Liberating Force at 8.00 am, and the unfurling of the Union Flag at 10.15 am.
Also recorded is Winston Churchill's memorable statement: "Our dear Channel Islands are also to be freed today."
At the east end of the seating the words "Thanks be to God" are inscribed in English and Guernsey-French.
The design of the Monument is not just specific to one day each year, but it is also unique to Guernsey. Nowhere else would the Sun cast a shadow in the precise curve at the precise times recorded by the inscriptions on the seating.
The Liberation Monument is in a location near the old Weighbridge Clock Tower at St Peter Port Harbour. It was in this area that islanders met the liberating forces in 1945 and rejoiced at their freedom.
It provides a pleasant place to sit in the sun, facing precisely due south.
The Monument is designed and positioned within about a hundredth of a degree (approximately one millimetre), giving a precision of just a few seconds in time. The accuracy will change slightly in the future, because of the effect of leap years, weathering, settlement, and changes in the Earth's rotation and orbit. However, it should be reasonably accurate for several hundred years - but only on the 9th May!
The monument was designed by Guernsey artist Eric Snell, and erected by the States of Guernsey Liberation Day Committee. The cost of the Monument was defrayed by public subscription.
A Path of Precision
(The bend in the shadow path before is because it jumps from the road level to the seating level.)
The large scale of the Liberation Monument,
which covers an area of 500 square metres (it extends over 40 metres from west
to east), and the fact that it is specific to just one day a year, gave the
opportunity for high precision in the shadow path of the tip of the obelisk.
The mathematical calculations required were carried out by David Le Conte, a member of the local astronomy society, the Astronomy Section of La Société Guernesiaise, using a (BBC Basic) computer program which he wrote specifically for the purpose. The program, called SunShadow calculated the position of the Sun every five minutes, from 0640 to 1700 hours British Summer Time, for
However, a mathematical calculation alone is not good enough for practical application. Factors unnoticed in a small-scale sundial affect the apparent length of the shadow of a large-scale instrument, and hence the position of the observed shadow tip. It was important to take these effects fully into account so that the shadow was seen to fall exactly where it was intended.
SunShadow already allowed for atmospheric refraction, and long-term changes in the shadow length were taken into account through calculations covering several hundred years. Leap years make a difference of course, but there are also long-term variations in the apparent position of the Sun. Other effects include the fact that the Sun is not a point source of light, diffusion of the shadow because of atmospheric haze, and the need for the top of the obelisk to have a minimum bulk in order to cast an umbral shadow. Extensive experiments were carried out to determine the optimum height and shape of the top of the obelisk.
The Construction - a Monumental Task!
Precision designing of the
A detailed analysis was carried out into the potential for errors to creep in during construction: height and perpendicularity of the obelisk, level of the base platform and seating, orientation of the seating, accuracy of manufacture, and placing of the inscriptions. The one remaining factor which could affect the Monument‘s accuracy in the future is subsidence. Jacking points were built into the foundations of the obelisk so that, if necessary, it can be restored to its correct position.
The States of Guernsey Architect, Patrick Reade, was responsible for overseeing the construction, and Surveyor Sean Harvey was assigned the critical task of laying it out. The direction of True North had to be determined to within 1/100th degree, and, because of uncertainties in the accuracy of the map grid, this was done by checking the position of the Pole Star against Mica, the US Naval Observatory’s Interactive Astronomical Almanac.
The building of the Monument was carried out by LeRoy Limited, under the supervision of Phil Sebire. Great care was taken in the stone cutting and construction, with frequent survey checks. Starting in September 1994, it was completed in time for final checks of the shadow appearance and position, and a grand unveiling on the 9th May 1995, the 50th Anniversary of the Liberation, by HRH The Prince of Wales, in the presence of thousands of islanders and visitors, including veterans of the War and of the Liberation.
Each year on the 9th May the
obelisk shadow silently commemorates the Liberation by following the precisely
delineated path, the shadow tip pointing at the designated times to the
inscribed events of 1945.
But the Monument serves a utilitarian, as well as a commemorative purpose. It is in a central location on the
Left to right: Phil Sebire, David Le Conte, Eric Snell, Peter Dodsworth, and Sean Harvey,
on 09 May 1995, before the unveiling
In 1997 the Monument won a coveted Civic Trust Award.
Further information about the
Monument appears in States of Guernsey Billet d'Etat
XVII, 1994. A full report on the
calculations of the shadow path and related data is lodged at the Guernsey
Greffe. Papers describing its design and
construction have been published in The
Review of the Guernsey
Society (Vol. LI, No. 2, Summer 1995, page 37), and the Bulletin
of the British Sundial Society (No. 97.3,
July 1997, page 43). The most detailed
paper is in the Report and Transactions
1997 of La Société Guernesiaise (Vol XXIV, Part II, page 309). There are brief descriptions in Guernsey Sundials by David & Dorothy Le Conte (published
by La Société Guernesiaise, 2004), Sundials of the
The award-winning Guernsey Sundial Trail
visitors since 25 May 2009.