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Subject: Re: chart scale information on charts...
From: Rodney Myrvaagnes (rodneym@XXX.XXX)
Date: Tue Apr 04 2000 - 11:47:26 EDT
It tells you the scale at a latitude that shows on the particular chart. The Mercator distortion can be measurable near the top and
bottom of small-scale Mercator charts, relative to the latitude of the scale.
For example, I am looking at 13324, "Tibbet Narrows to Schoodic Island"
Scale is 1:40,000 at 44-28 north. That is pretty close to the middle of the chart, which extends from 44-15 to a little more than 44-
39.
Oblateness error would never be big enough to measure withing any reasonable Mercator chart. Other projections are used for
long-distance charts.
On Tue, 4 Apr 2000 15:51:40 +0200, Russell Sher wrote:
>I have a small question about the chart scale as displayed on mercator
>charts:
>Normally the scale on the chart is displayed as that scale given according
>to a particular latitude for example
>1: 750 000 (at 34 deg 00' S), thus implying that the scale is calculated for
>the length of latitude at the given value (in this case 34 deg 00').
>My question is - Is the scale stated in this way due to the mercator
>distortion as one travels away from the equator (due to the nature of the
>projection), or is the scale stated in this way due to the (slight) change
>in the value of a minute of latitude due to the oblate shape of the earth?
>
>Regards
>Russell
>
Rodney Myrvaagnes J36 Gjo/a
Senior Editor Electronic Products
My oyster knife is Y2K compliant
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