Astrogeodetic study of the orientation of ancient and Byzantine monuments: methodology and first results

This work presents a method for the thorough research of the orientation of monuments, based on state-of-the-art geodetic and astronomical measurements. These measurements permit the production of an astronomically oriented, digital plan of the monument, a digital diagram of the perceptible horizon around the monument and a digital reconstruction of the apparent path of the Sun, as it rises above the horizon at characteristic dates. The data reduction procedures are rigorous and lead to an accurate determination of the orientation of the monument. The orientation is then interpreted in terms of other, mostly cultural, information about the scope of the monument and its time of construction. In retrospect, therefore, the method provides an independent determination of the time of construction of the monument within a narrow chronological range. The effectiveness and accuracy of the method is demonstrated by its application to the late Byzantine church of the “Assumption of Virgin Mary” in the Greek town of Kalabaka. The orientation of the main axis of the church is geometrically determined to an accuracy of 0.6 arcminutes. Combining all geometric data with cultural and historical information, we determine the time of construction of the church (1000 AD ± 13 years).