----- Forwarded Message -----
From: "Jan Smits" <[log in to unmask]>
To: "Air Photo & GIS Forum Maps" <[log in to unmask]>
Sent: Sunday, December 20, 2009 8:40:43 AM GMT -06:00 US/Canada Central
Subject: RE: need help with scale in pas geometriques
Trying to give scales for pre-1800 maps implies always 3 to 4 measurements and should result in phrases as 'Scale varying from [ca. 1:7,400] to [ca. 1:8,400]' when derived from measurements on modern maps. Or 'Scale [ca. 1:7,900], measurement derived from scale bar (900 rods = 33 mm)'. When the scale bar is not used in this way its mention should be relegated to the notes.
I advise curators and editors of facsimiles to be careful with scales and never to use one scale denominator when the map does not have a geometrical basis based on triangulation. When the cataloguer is not sure it is better to state 'Scale unknown' and give a scale-bar note than giving a quizzing approximation with which nothing can be proved or which creates confusion.
From http://persons.kb.nl/jsmits/skd/mathemat.html
Jan Smits
Koninklijke Bibliotheek, National Library of The Netherlands
________________________________
Van: Maps, Air Photo & GIS Forum namens Angie Cope
Verzonden: vr 18-12-2009 19:04
Aan: [log in to unmask]
Onderwerp: need help with scale in pas geometriques
-------- Original Message --------
Subject: need help with scale in pas geometriques
Date: Fri, 18 Dec 2009 10:09:43 -0700
From: [log in to unmask]
To: MAPS-L <[log in to unmask]>
Hi there,
I'm a rare book cataloger, who recently started working with
cartographic materials.
I typically work with atlases, so scale is hardly ever an issue. But,
when it is, I often have to
convert foreign and/or archaic units, a bit challenging to say the least
...
I'm pretty much a novice, so please bear with me.
I am trying to supply the RF for bar scale given in pas geometriques,
for maps from La Caille's Description de la ville et des fauxbourgs de
Paris,
(1967 facsim of 1714 ed)
The maps that show scale have 2 bar scales that vary between 2 1/8-2 1/4
in. in length.
Top one reads "quatre cents pas geometrique", the one under it reads
"mil pas communs".
According to my research 1 pg = 5.33 ft /63.96 in
and 1 pc = 2.66 ft / 31.98 in.
An in on the pg bar scale = approx 180 pg
So if I multiply 180 x 63.96, I get 1:11,513.
Am I totally off here?
Any help would be *really* appreciated.
-Silvana
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