[ISHMap-List] list serve message re: bicentenary Rizzi Zannoni

Oliver, Richard R.R.Oliver at exeter.ac.uk
Mon Jan 20 08:56:15 CET 2014

The method used by the Ordnance Survey of the United Kingdom was a combination of rigorous primary-level triangulation combined with zenith-sector observations of various stars. This was published in a monumental tome in 1858. If anyone 'out there' thinks this is an inadequate answer, then it may well inidicate why the subject has been neglected: many of we 'historians of carography' and allied matters have been historians or geographers rather than mathematicians or geodesists!

Richard Oliver
(B.A. and D.Phil., with a distinct bias towards 19th century political history...)
From: ishm-bounces at lazarus.elte.hu [ishm-bounces at lazarus.elte.hu] on behalf of Douglas Sims [dougsims1945 at yahoo.com]
Sent: 18 January 2014 22:55
To: Mary Pedley; ishm at lazarus.elte.hu
Cc: Vladimiro Valerio
Subject: Re: [ISHMap-List] list serve message re: bicentenary Rizzi Zannoni

January 18, 2014

Dear ISHMappers, Mary, and Vladimir,

Concerning the January 24 erecting of a plaque to indicate the spot where Rizzi-Zannoni established his meridian line:  Is it planned to publish any papers in connection with this, especially anything telling us what procedure(s) Rizzi-Zannoni used in obtaining his meridian line?  As implied by Vladiniro, certainly he could not hope to establish a longitude difference between his point and any others with much accuracy without a reliably marked meridian for his location.  Thus, there was incalculable importance in the job of getting this line as accurately as possible.

In my experience, the question of establishing a meridian line is treated in our literature rather like the question of the determination of mean solar time, both essential to finding longitude differences..  Both are often treated as somewhat taken for granted, and it is assumed without a second thought that some simple and certain procedure exists.

Actually, as some ISHMappers will know, they are excruciatingly difficult things.  As to the meridian line, obviously, one could not have simply used a compass.  Far too shaky, and, besides, though the existence of magnetic declination was recognized, it was far from being understood.  As far as I know, the method usually used  was some sort of equal-altitudes maneuver.  But here too, since the earth is spinning constantly, and human beings tend to slightly quake, one is much limited in obtaining the necessary degree of accuracy in the instantaneous altitudes that he takes, and assuring that they are taken exactly at the right instant.

A good indication of the tremendous difficulty of this is the simple fact that almost no one, among the old geographers and astronomers consulted by me (a good number), ever explains the method that he used.  This, although the finding of this line as accurately as possible is essential to not just map-making, but also to other things, such as founding observatories, compiling ephemerides, themselves also in the end essential to accurate map-making.

This is a silence which speaks loudly to me.  The impression I receive is that our scholars usually simply pass over this all-important thing in silence, apprehensive that he will come under criticism for taking insufficient pains if he describes the procedure used in detail.  He feels, I suspect, that virtually all readers will fail to notice the omission, an omission oddly just as unnoticeable as it is enormous.  To the matter of increasing coordinate accuracy over the centuries, certainly we have here the germs of a virtually unexplored, but vital, element.

I have devoted much time to this question, and shall again as soon as other exigencies allow it.  Thus my great interest in finding out if, during the Rizzi-Zannoni commemorative activities, there will be any publications released, in particular in connection with the question of exactly what method(s) Rizzi-Zannoni used in finding his line.

Thank you,

Doug Sims

Douglas W Sims
3516A Bayview Avenue, apt. F
Brooklyn, New York, 11224

On Saturday, January 18, 2014 10:06 AM, Mary Pedley <mpedley at umich.edu> wrote:
Dear colleagues:

Please find the attached announcement from Vladimiro Valerio regarding the opening celebrations of the bicentenary of the death of geographer and cartographer Giovanni Antonio Rizzi-Zannoni (1736-1814).

On the 24th of January a plaque will be placed at the Castel Sant'Elmo in Naples, Italy, to mark the spot used by Rizzi-Zannoni to establish the meridian line and center of the coordinates for his new map of the Kingdom of Naples (1787-1812). The ceremony at Castel Sant'Elmo will inaugurate a year of celebratory activities honoring the Italian geographer with renewed study of his life and works.

Thank you.

Mary Pedley
Mary Pedley
Map Division
William L. Clements Library
The University of Michigan

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