-------- Original Message --------
Subject: Fwd: converting a verbal scale statement -- help needed!
Date: Thu, 18 Dec 2008 14:28:01 -0500
From: lucia lovison <[log in to unmask]>
To: [log in to unmask]
CC: Lucia <[log in to unmask]>
References: <[log in to unmask]>
<[log in to unmask]>
Hi:
I sent out the message below to Andrew Paige, but since this
discussion has taken a life of its own, I share with you my
considerations -- my approach is different from the one outlined in
some e-mail.
As you see, I tried to come up with numbers because I think that was
the intent of the cartographer.
To further constraint the solution, we need to have more critical
information from Andrew (please see my points 1-2-3 in "your question
does not tell us..").
Happy Holidays to all.
Lucia Lovison-Golob
Project Director
Afriterra Foundation
http://www.afriterra.org
[log in to unmask]
---------- Forwarded message ----------
From: lucia lovison <[log in to unmask]>
Date: Thu, Dec 18, 2008 at 1:24 PM
Subject: Re: converting a verbal scale statement -- help needed!
To: [log in to unmask]
Cc: [log in to unmask]
Hi Andrew:
Here is my take.
1 Marine league (assuming it refers to a U.S. or English cartographer)
= 3 marine, or geographical, miles of 6080 feet each. 1 foot = 0.3048
m
Therefore:
1 Marine league (assuming it refers to a U.S. or English cartographer)
= 3x 6080x0.3048m = 5,559.552m or 5.559 Km
Your question was: "Marine Leagues 20 to a degree"
Second mail:
"MARINE LEAGUE. A measure equal to the twentieth part of a degree. Bouch.
Inst. n. 1845, not. Vide Cannon Shot; Sea."
Approach one:
1- you need to know the region to which the map refers: let's say that
is mid latitude.
if at 40 degrees (North or South) = 111.03 Km
1/20 of 111.03 Km = 5.5515 Km
but if at 50 degrees (North or South) = 111.23 Km
1/20 of 111.23 Km = 5.5615 Km
Approach two:
2- 5.559 Km (1 marine League)= 1/20 of 1 degree (of latitude).
Therefore:
X= 0.02795 degree of latitude (in decimal degrees)
So, one marine league corresponds to 0.02795 degrees of latitudes.
Your question does not tell us:
1-where the cartographer comes from (marine leagues range in size
depending on the different country).
2- the degree to which refers to, probably one degree of latitude (the
number 1 is omitted but we can also assume that the cartographer meant
exactly 1). 1845 date of the map (we assume that the cartographer
refers to latitude, because it is easier to measure, not to longitude)
3- the general geographic region (so you can constraint the size of
the marine league, if we follow approach 1).
If 2-assumption is correct, than the map must refer to mid-latitudes because:
1-If 5.559km corresponds to 1/20 of a degree, then there are 111.19104
Km for one degree.
2- We know that:
1 degree of latitude at 40 degrees (North or South) = 111.03 Km and 1
degree of latitude at 500 (North or South) = 111.23 Km
Therefore, by approximating the arc of latitude to a line, we get that
the measure corresponds approximately to a degree of latitude 48
degrees (North or South). (It is a way to check if all or any of the
assumptions are correct). If not, you can play by relating one of the
three assumptions and see if it makes sense with the information on
map that you have.
Happy Holidays, Andrew!
Lucia
On Thu, Dec 18, 2008 at 12:36 PM, Maps-L Moderator <[log in to unmask]> wrote:
> -------- Original Message --------
> Subject: Re: [MAPS-L] converting a verbal scale statement -- help
> needed!
> Date: Thu, 18 Dec 2008 11:20:25 -0600
> From: Robert Wyatt <[log in to unmask]>
> Reply-To: [log in to unmask]
> To: [log in to unmask]
> CC: [log in to unmask]
> References: <[log in to unmask]>
>
>
>
> 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.
>
> Maps-L Moderator wrote:
>>
>> -------- Original Message --------
>> Subject: converting a verbal scale statement -- help needed!
>> Date: Thu, 18 Dec 2008 11:22:12 -0500
>> From: Paige Andrew <[log in to unmask]>
>> To: [log in to unmask]
>>
>>
>>
>> Good morning!
>>
>> I'm trying to assist a new maps cataloger with converting a verbal
>> scale statement on some early charts and am honestly all turned
>> around with this. The statement on the map is:
>>
>> "Marine Leagues 20 to a degree"
>>
>> From what she attempted I honestly think she has come up with a
>> pretty accurate figure, but I'd like those folks on this list who
>> have much more experience in doing conversions of non-mile stuff to
>> work this over and share your answer(s), and the process to getting
>> to them, to this list please. Thanks!
>>
>> Thoroughly confused,
>>
>> Paige
>
|
