-------- Original Message --------
Subject: RE: converting a verbal scale statement -- help needed!
Date: Thu, 18 Dec 2008 14:14:07 -0500
From: Grabach, Kenneth A. Mr. <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
References: <[log in to unmask]>
I think for the purposes of a nautical chart, one can stick with a standard unit for a degree (that is what the statement on the chart is, otherwise it is pointless to include it, and navigators are mathematicians if nothing else). In fact, this measurement, of 20 marine leagues to degree, if it is 60 (nautical) miles, then this is working in the same base 60 as the degrees themselves.
The other half of the ratio is on the map itself. How long is the distance of a degree on the chart? That distance represents 20 marine leagues or 60 nautical miles. It doesn't matter whether this is a degree of latitude or longitude if it is a nautical chart done in Mercator projection, as the distances are the same in all directions. That is why this projection was devised, to make distances easier to compute and directions drawn as straight lines for navigators.
Ken
Ken Grabach <[log in to unmask]>
Maps Librarian Phone: 513-529-1726
Miami University Libraries
Oxford, Ohio 45056 USA
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Sent: Thursday, December 18, 2008 2:05 PM
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Subject: Re: converting a verbal scale statement -- help needed!
-------- Original Message --------
Subject: Re: converting a verbal scale statement -- help needed!
Date: Thu, 18 Dec 2008 13:54:48 -0500
From: John Hamilton <[log in to unmask]>
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References: <[log in to unmask]>
I must say, I agree with Robert; I also think the phrase "Marine
Leagues 20 to a degree" is not a statement of scale. 20 marine
leagues would be about 60 miles, and degrees are about 69 miles apart
at the Equator (it varies), narrowing to zero at the poles. Since the
distance between degrees varies, knowing the distance between degrees
would be helpful, but doesn't seem to represent a scale. I just can't
see how to compute a scale without some information about the
distance on the map itself. Aren't we given only half the ratio?
I'll be happy to be proven wrong, though; it is an interesting problem.
John Hamilton
Cataloging and Metadata Services
Penn State University Libraries
>I'm thinking it's not a scale statement; but rather just a statement.
>
>found on the net:
>MARINE LEAGUE. A measure equal to the twentieth part of a degree. Bouch.
>Inst. n. 1845, not. Vide Cannon Shot; Sea.
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