Dear
All,
Some time
ago, a list member gave the following definition of a 'singleton
dial' - "it's a
horizontal dial with polar-pointing style and showing standard time on 12 date
rings" Also, in the BSS glossary of dials, key characteristics of dials
physical construction are highlighted to explain the set of dials that belong to
one dial type.
Classification of
dials based on physical characteristics is a way of recognising basic types
of dials.
I am
considering the question -
"How many
dimensions are necessary to classify the types of sundials?"
The
following 4 dimensions (domains) come to mind quickly:
*dial
principle
shadow
transmission (light beam through a hole)
reflective
diffraction
*dial
plate
-planar
- horizontal
- inclined
- vertical
-cylinder
- polar
- vertical
-hemisphere
-arbitary hollowed out surface
*gnomon
-point
- fixed
- movable
-segment
- polar
- vertical
- fixed
- movable
*hour markers
-point
-segment
- curve
-analemma
-figure 8
- half
- equation
of time
-unfolded "analemma"
Example
classifications using the above 4 dimensions
Horizontal Dial:
principle:shadow, dial:planar-horizontal, gnomon: segment-polar, hour markers:
segment
Analemmatic Dial:
principle:shadow, dial:planar-horizontal, gnomon: segment-vertical(movable),
hour markers: point
Shepherd's Dial:
principle:shadow, dial:cylinder-vertical, gnomon: point-movable, hour markers:
solar altitude curve
Is 4 dimensions
enough to separate all the various types of dial? Almost certainly
not. What is the minimum set of other (semi) orthogonal dimensions can be
added to classify known dial types?
Has any work been
done on this by others?
In this endeavour,
careful attention to separating 'classifying dimensions' from 'dial
attributes'. Attributes 'flow from' key classifying characteristics of the
dial construction. Eg. 'self aligning' is probably not a classifying
dimension, as it arises as a consequence of the nature of construction, rather
than being an observable classification dimension.
Thanks
David Pratten
====================================
David Pratten
Phone:
+7 (3272) 46 04 20
Fax (auto forwarded): +1 (603) 676-1231
Postal: PO Box
21, Almaty 480057, KAZAKHSTAN
