---------- Forwarded message ----------
Date: Wed, 23 Sep 1998 17:02:11 EDT
From: [log in to unmask]
To: [log in to unmask]
Subject: Re: MM: Mapping on truly small and large scales (fwd)
 
Regarding Wil Tirion's sky atlases, you wrote,
"This must be the smallest-scale niche in cartography."
 
I realize that you were just opening a light-hearted discussion, but I do have
to say that I wouldn't agree with this statement. An atlas of the sky is an
angular map (another way of saying this is that the "celestial sphere" has no
radius). Now when you hold an atlas at normal viewing distance, say 18 inches,
you discover that 4 inches covers about 13 degrees on the "Sky Atlas 2000"
charts. 4 inches at at a distance of 18 inches also corresponds to an angle of
just about 13 degrees. In other words, the scale of "Sky Atlas 2000" is 1:1
--quite a large scale chart. If you're looking for a correspondence with
something in terrestrial cartography, a star chart is more like one of the
perspective drawings of ports that used to appear on old nautical charts.
 
So what about truly small-scale linear maps? There are "maps" of nearby stars
(drawn from a sort of omniscient, outside the galaxy viewpoint) and there are
even "maps" of distributions of quasars where objects at distances of billions
of lightyears are shown just a few inches apart. That's really the smallest
usable scale you could have. Given the constraint that the observable universe
is only about 25 billion lightyears across and a usable map size is not much
smaller than 4 inches, the smallest map scale, for this universe at least, is
1:2,000,000,000,000,000,000,000,000,000. For a sample of a few such
astronomically-scaled maps (just the local stars, so the scale is merely
1:200,000,000,000,000,000), take a look at my stereoscopic maps of nearby
stars. It's the first item at www.clockwk.com/science.htm.
 
" What is the largest? Can cartographic or GIS tools and methods be used on
the other end of the scale spectrum? Mapping bacterial growth in a culture
would be pretty large scale, but how about mapping in truly microscopic
realms? "
 
True cartographic and GIS tools? I can't imagine anyone doing that on "truly
microscopic" scales. Of coure, there are diagrams in nuclear physics which
employ, for example, polar coordinate systems for things as small as protons,
but physicists deal in such things without reference to any cartpgraphic
antecedents. It's just math. In the end, this gets down to the old, endless
discussion what is a map. Surely, one wouldn't claim every scientific or
technical diagram with coordinates on it to be an example of the mapmaker's
art.
 
While we're at it, those of us who have become cartographers after starting
out in other scientific or technical professions are almost invariably annoyed
by the use of the expression "scale" to describe a map. On paper maps, this
served a useful, immediate purpose. But the retention of this terminology for
digital mapping products is almost meaningless. What does it mean to say that
the DCW (etc.) mapping products are 1:1,000,000 scale? Even if you look at the
details of the scanning method, the smallest features certainly do not
correspond to the smallest features on high-quality paper maps scaled at
1-to-1million. Eventually, cartography will have to adopt the concept of
resolution --a map's quality is defined by the smallest detail that it can
faithfully resolve (or the smallest distance between neighboring items that it
can distinguish separately). A map can be printed or reproduced at almost any
linear scale today. But the resolution remains the same.
 
-FER
www.clockwk.com/fer