title: North error estimation based on solar elevation errors in the third step of sky-polarimetric Viking navigation.
abstract: The theory of sky-polarimetric Viking navigation has been widely accepted for decades without any information about the accuracy of this method. Previously, we have measured the accuracy of the first and second steps of this navigation method in psychophysical laboratory and planetarium experiments. Now, we have tested the accuracy of the third step in a planetarium experiment, assuming that the first and second steps are errorless. Using the fists of their outstretched arms, 10 test persons had to estimate the elevation angles (measured in numbers of fists and fingers) of black dots (representing the position of the occluded Sun) projected onto the planetarium dome. The test persons performed 2400 elevation estimations, 48% of which were more accurate than ±1°. We selected three test persons with the (i) largest and (ii) smallest elevation errors and (iii) highest standard deviation of the elevation error. From the errors of these three persons, we calculated their error function, from which the North errors (the angles with which they deviated from the geographical North) were determined for summer solstice and spring equinox, two specific dates of the Viking sailing period. The range of possible North errors ΔωNwas the lowest and highest at low and high solar elevations, respectively. At high elevations, the maximal ΔωNwas 35.6° and 73.7° at summer solstice and 23.8° and 43.9° at spring equinox for the best and worst test person (navigator), respectively. Thus, the best navigator was twice as good as the worst one. At solstice and equinox, high elevations occur the most frequently during the day, thus high North errors could occur more frequently than expected before. According to our findings, the ideal periods for sky-polarimetric Viking navigation are immediately after sunrise and before sunset, because the North errors are the lowest at low solar elevations.
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute , Eötvös University , Pázmány sétány 1, 1117 Budapest, Hungary.
authors: Dénes
authors: D
authors: Száz
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Pázmány sétány 1, 1117 Budapest, Hungary; MTA Centre for Ecological Research, Danube Research Institute, Karolina út 29-31, 1113 Budapest, Hungary.
authors: Alexandra
authors: A
authors: Farkas
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Pázmány sétány 1, 1117 Budapest, Hungary; Estrato Research and Development Ltd, Németvölgyi út 91/c, 1124 Budapest, Hungary.
authors: András
authors: A
authors: Barta
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute , Eötvös University , Pázmány sétány 1, 1117 Budapest, Hungary.
authors: Balázs
authors: B
authors: Kretzer
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Pázmány sétány 1, 1117 Budapest, Hungary; MTA Centre for Ecological Research, Danube Research Institute, Karolina út 29-31, 1113 Budapest, Hungary.
authors: Ádám
authors: Á
authors: Egri
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute , Eötvös University , Pázmány sétány 1, 1117 Budapest, Hungary.
authors: Gábor
authors: 0000-0002-9008-2411
authors: G
authors: Horváth
keywords: North estimation; Viking navigation; sky polarization; solar elevation; sunstone