-------- Original Message --------
Subject:        Re: question about determining scale
Date:   Thu, 12 Dec 2013 17:48:10 +0000
From:   Mark Jackson <[log in to unmask]>
To:     Maps, Air Photo, GIS Forum - Map Librarianship
<[log in to unmask]>



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
801.422.9753 ∙ [log in to unmask] <mailto:[log in to unmask]>


On Dec 12, 2013, at 5:52 AM, Angie Cope, American Geographical Society
Library, UW Milwaukee <[log in to unmask] <mailto:[log in to unmask]>> wrote:

>
> -------- Original Message --------
> Subject:      question about determining scale
> Date:         Tue, 10 Dec 2013 18:23:02 -0500
> From:         Manon Theroux <[log in to unmask]>
> To:   [log in to unmask]
>
>
>
> 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
>
> ------------------------------
>
> 2 000 yards in units of the bar scale
> <http://desktop.loc.gov/template.htm?view=document&doc_action=setdoc&doc_keytype=foliodestination&doc_key=cartmatsBarSPACEscale&hash=BarSPACEscale>
>
> 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
>
>
>
>