Analysis of Structures’ Orientations in Archaeoastronomy

In the scope of archaeoastronomy, the analysis of a large number of structures through the frequency histograms for their azimuths and declinations can identify singular patterns of orientation. Conclusions often rely on qualitative assessments. Quantitative assessments have been proposed by using as null hypothesis a pure random distribution of azimuths over the 360º horizon. In some cases, such as orientation of Christian churches, the histograms or spectra are composite, with peaks overlapping a continuous and not uniform background. This paper presents a methodology for assessing the statistical significance of the net area of a peak in the histogram in relation to the local background level. The spectra use Normal kernel functions. The background contribution is estimated from the area of the trapezoidal polygon under the peak, and it is interpreted as the probability parameter for a Binomial distribution.  The methodology is illustrated with a real case study which includes the azimuth and declination histograms for a set of churches from southern Spain dedicated to the Virgin of the Assumption. The method is more restrictive than previous approaches.