ARCHEOASTRONOMIA LIGUSTICA
Articolo presentato al XIII Convegno SIA tenutosi a Sassari
nell’anno 2013 e pubblicato in: Cronache di Archeologia nr. 11, La
misura del tempo. Atti del III
Convegno Internazionale di Archeoastronomia in Sardegna e XIII Convegno SIA,
parte I, Mediando Srl, Sassari, dic. 2014, ISBN 978-88-89502-78-5, pp. 217-221.
MULTILEVEL
ARCHEOASTRONOMICAL PRE-ANALYSIS OF THE ROMANESQUE CHURCH OF SAN PARAGORIO IN
NOLI
Mario Codebň
RIASSUNTO
Questo articolo
doveva in origine essere il confronto tra le misure della chiesa romanica di S.
Paragorio di Noli (Savona) prese con tre metodi
differenti e da tre autori diversi: Riccardo Balestrieri, Mario Codebň ed Adriano Gaspani. Doveva
inoltre correggere un errore presente in un precedente articolo (Bonora, Codebň, De Santis, Gaspani, Marano Bonora, Medioli 2006a, pp. 38 – 49). A
causa del ritiro di Balestrieri e Gaspani, viene da
me presentato esclusivamente come errata corrige.
INTRODUCTION
Initially this report had to be:
1) the comparison between the measurements of the
church of St. Paragorio of Noli
(Savona, Italy) got using three different methods of measurement:the
satellite one, the GPS one and the classical one;
2) the correction of a mistake in the previous report
(Bonora, Codebň, De Santis, Gaspani, Marano Bonora, Medioli 2006a, pp. 38 – 49).
Because the retirement of Balestrieri
and Gaspani[1],
it is only an errata corrigenda.
The difference between the azimuth 107,9° that Balestrieri got with his Satellite Method (http://uranialigustica.altervista.org/edifici/schede/sv_s-paragorio.htm)
and the azimuth 104,36° that Gaspani got with his GPS
Method (Bonora, Codebň, De Santis, Gaspani, Marano Bonora, Medioli 2006a, p. 47, tab 1) is 3,54°: too much to rule out
a mistake. Performed the calculation again, it resulted that the geographical
coordinates of Bergeggi island, that was used as “far
end” of the baseline of the GPS Method, were wrong in the used topographic map
1:25000 of Istituto Geografico
Militare IGM (Military Geographic Institute). In fact
these coordinates are a little different in longitude from those obtained from
other sources[2]:
Tab No. 1: Bergeggi Island’s geographical
coordinates and maps[3]
|
Map |
Latitude |
Longitude |
|
IGM[4]
1:25000 n. 92ISE Finale L. |
φ
44°14’00,81”N |
λ 8°27’28,3”E |
|
IIM[5] 1:250000
909INT3300 |
φ 44°13’54’N |
λ 8°26’42”E |
|
CGI[6]
1:100000 Fogli 92–93 |
φ 44°14’00”N |
λ 8°26’47,63”E |
|
CTR[7]
1:50000 n. 229–246 Savona |
φ
44°14’06,49”N |
λ 8°27’18,5”E |
|
Google Earth |
φ
44°14’02,72”N |
λ 8°26’42,24”E |
The Satellites Method is based on measurements by satellite pictures in
Google Earth. Its disadvantage is the (perhaps) lower accuracy than the others
two. Its advantage is the possibility to measure well–preserved monuments
everywhere in the world “without leaving own home”.
The GPS Method is based on the construction of a long baseline (some
kilometres) between two points, the geographical coordinates of which are
well–known (the far one of them by a topographic map; the proximal one of them
by GPS), and on the measurement with a theodolite (or with another similar
instrument for azimuthal measurements) of the angle between this baseline
(which azimuth can be calculated easily) and the axes of a monument. Its
disadvantage is a perhaps lower accuracy than the Astronomical Method (at the
same tools used); its advantage is that it can be used under a cloudy sky.
The Astronomical Method or Classical Method consists of the algebraic
sum of the angle between the axes of a monument and
an heavenly body – generally the Sun – and on the calculation of the
astronomical azimuth of this heavenly body using the Nautical Method (Codebň 1997; Codebň and Frosini 2014)[8]
or the JD Method (Codebň 2010). The result is the
astronomical azimuth of the axes of the monument. It disadvantage is that it is
usable only in good weather conditions (no clouds!); its advantage is that it
is perhaps the most accurate (according to the accuracy of the measuring
instrument that is used).
ASTRONOMICAL MEASUREMENTS
03 June 1998 we had measured (Bonora, Codebň, De Santis, Gaspani, Marano Bonora, Medioli 2006a) St. Paragorio Church – latitude 44°12’16”N; longitude
8°24’58”E; altitude 5 m above sea level[9]
– by the “classical” astronomical method too, using:
1) a theodolite Meopta T1c (for azimuthal and zenithal angles);
2) a graduated spherical surveyor’s cross (only for azimuthal angles);
3) a clinometer (only for the zenithal
angles);
4) the Nautical Method for the calculations.
Meopta T1c theodolite nominal accuracy is 1c, i.e.
0°00’32,4”.
Graduated spherical surveyor’s cross nominal accuracy is 5c, i.e.
0°02’42”.
Clinometer nominal accuracy is 1°.
Unfortunately, today we cannot distinguish any more the measurements by
theodolite from the ones by graduated spherical surveyor’s cross. Therefore, in
next tables results are mixed.
Tab. No. 2: measurements seaward[10]
|
Axes of… |
local time tm |
instrumental angle αg[11] |
Instrumental angle α° |
Resultant azimuth of the buildings |
Inverse azimuth |
|
Outside
eastern wall |
16h32m16s |
160,85g |
144°45’54” |
111,3° |
291,3° |
|
Outside
western wall |
16h47m33s |
167,95g |
151°09’18” |
108,1° |
288,1° |
|
Nave from
West outside |
16h57m25s |
172,90g |
155°36’36” |
105,7° |
285,7° |
|
Nave from
East outside |
17h00m45s |
171,75g |
154°34’30” |
107,4° |
287,4° |
|
Ridge from the outside[12] |
17h04m36s |
175,85g |
158°15’54” |
104,4° |
284,4° |
Tab No. 3: measurements mountainward
|
Axes of… |
local time tm |
instrumental angle αg |
Instrumental angle α° |
Resultant azimuth of the buildings |
Inverse azimuth |
|
Nave from
West outside 1[13] |
18h33m30s |
2,07g |
1°51’46,8” |
276,4° |
96,4° |
|
Nave from
West outside 2[14] |
18h35m50s |
3,40g |
3°03’36” |
275,6° |
95,6° |
|
Nave from
East outside |
17h45m49s |
20,89g |
18°48’10,08” |
289,1° |
109,1° |
|
Ridge from the outside |
17h39m00s |
18,55g |
16°41’42” |
285,7° |
105,7° |
CONCLUSION
The mean
azimuths of the church resultant from seven “classical” astronomical azimuths
eastwards and westwards of tables No. 2 and 3, rejecting the two measurements of
the nave from West outside in the table No. 3 because too much different from
the others (i.e. wrong), are: 287,4° and 107,4° σ ±2,2°[15].
This azimuth is in a very good agreement with the azimuth 107,9° σ ±2° got by Balestrieri.
The azimuth of the
church in the CTR topographic map 1:5000 Noli (No.
229132) is 107° and 287°.
Magnetic mean
azimuths of the same buildings, with Wilkie prismatic
compass (1° accuracy), is 107°±3° (five measurements) and 286,5°±2° (two
measurements).
Therefore, St. Paragorio’s right azimuth is 107° and not 104°, as it is
wrongly written in our previous report (Bonora, Codebň, De Santis, Gaspani, Marano Bonora, Medioli 2006a, p. 47, tab
1) because the wrong coordinates of Bergeggi Island.
REFERENCES
·
Bonora
V., Codebň M., De Santis
H., Gaspani A., Marano Bonora A., Medioli D. 2006a, Simbolismo
mistico e orientazioni astronomiche nella chiesa romanica di S. Paragorio a Noli (SV) , in “Atti del IV Congresso
Nazionale della Societa Italiana di Archeostronomia”, ConTatto
Edizioni, Lerici (SP), settembre 2006, pp. 38-49.
·
Bureau International des Poids et Mesures 2006b, The International System of Units (SI),
8th edition.
·
Codebň M. 1997,
Problemi generali del rilevamento archeoastronomico, in “Atti del I Seminario
A.L.S.S.A. di Archeoastronomia”, Genova 22 febbraio 1997, pp. 17-39.
·
Codebň M. 2010.
L’algoritmo
giuliano del sole, in “Atti del XII seminario A.L.S.S.A. di
Archeoastronomia”, Genova 17-18 aprile 2010, pp. 36-50.
·
Codebň M.,
Frosini A. 2014, Il metodo nautico (per il
calcolo dell’azimut di un allineamento e della declinazione da esso sottesa), in “Atti del XV Seminario
A.L.S.S.A. di Archeoastronomia”, Genova 13-14 aprile 2013, pp. 152-170.