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I’m no cataloger, but as a geographer I use maps heavily and
have taught map use and aerial photo interpretation courses for
years, etc. Every map and image etc. generally has an average
scale, but will vary a bit around the map depending on
projection, the material it is printed on, topography, etc.
You’re email didn’t come through with any images, so I’m not
seeing what you are seeing, but looking at that I’d say that
whatever map you are using is clearly meant to be a 1 inch (map)
= 1 mile (Earth), or 1:63,360, which is what I’d be looking for
in the catalog anyway.
The ruler I commonly use with imagery and maps is divided
into 10ths and 100ths of an inch but will commonly use a loupe
and go for the thousandths digit. That is more for imagery than
maps where the width of the ink line can make a huge difference.
In this case a scale bar representing 2000 yards would need to
be 1.1363636 inches to equal 1 mile on the ground. So, if you
kind of measure from the center of the ink lines on each end of
the scale bar you could come down from 1.14 to 1.137 and you’d
come up with 1”=1 mile or 1/63,360.
Hopefully that helps.
--
Dr. Mark Jackson
Research Librarian
Geography ∙ Geology ∙ Civil Engineering ∙ CM ∙ FPM ∙ IT
Brigham Young University
2420 HBLL ∙ Provo UT 84602
On Dec 12, 2013, at 5:52 AM, Angie Cope, American
Geographical Society Library, UW Milwaukee <
[log in to unmask]>
wrote:
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For those of you familiar with the "Cartographic
Materials" rules for cataloging maps, I have a
question about determining a representative fraction
using a bar scale. I've copied below example #2 from
Appendix B (Guidelines to Determine Scale and
Coordinates), B2B (Conversion from a graphic scale). I
don't know if the formatting will come through or not,
so you might have to check your copy of CM. When I try
to replicate the math, my calculator gives me
"63,1578947368" for the right hand side. Rounding that
off would give me a representative fraction of
1:63,158. Can anyone explain why CM gives 1:63,157 as
the RF? Is there a reason you would round down?
Also, I'm curious, how likely is it that a map
cataloger would have a ruler that measures to the
accuracy of 1.14 inches anyway?
Thanks in advance for any help you can provide,
Manon Theroux
Head of Technical Services
U.S. Senate Library
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measure
1.14 inches with a ruler.
1.14
inches (on map) represents 2 000 yards (Earth)
2 000
yards = 2 000 × 36 inches
The ratio
is: 1.14:(2 000 × 36)
or
or
1:63
157