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List: postgis-users
Subject: Re: [postgis-users] drawing nautical data on projection
From: Dave <dave.potts () pinan ! co ! uk>
Date: 2011-04-29 8:05:03
Message-ID: 4DBA712F.1070906 () pinan ! co ! uk
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I think I have a solution to this issue
I am going to convert my point origin to meter based projection (eg
google 900913), create my line data, then transform it back to the 4326
projection, in this way the scale factors calculations should be done
by the proj library.
Does this sound like a decent solution?
On 28/04/2011 10:48, Dave wrote:
> I have some line data measured in nautical miles.
>
> I want to draw these points on a map using the 4326 projection, the
> srs entry for this projection gives the unit of measurement as degree.
>
> A nautical mile is one minture of an arc of lattitude ie 0-60, the
> projection is measured in 0-100.
>
> So does this mean that when I want to draw a line measured in nautical
> miles, I have map 0-60 on to 0-100 grid , ie I have to apply 0.6
> factor ?
>
> So a line starting at lat 1.2 and ending at lat 2.7 becomes a line
> 1.12 to 2.42 ?
>
> regards
>
>
> Dave.
>
>
>
> _______________________________________________
> postgis-users mailing list
> postgis-users@postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
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I think I have a solution to this issue<br>
<br>
I am going to convert my point origin to meter based projection (eg
google 900913), create my line data, then transform it back to the
4326 projection, in this way the scale factors calculations should
be done by the proj library.<br>
<br>
Does this sound like a decent solution?<br>
<br>
On 28/04/2011 10:48, Dave wrote:
<blockquote cite="mid:4DB937FE.2050007@pinan.co.uk" type="cite">
<meta content="text/html; charset=windows-1252"
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I have some line data measured in nautical miles.<br>
<br>
I want to draw these points on a map using the 4326 projection,
the srs entry for this projection gives the unit of measurement as
degree.<br>
<br>
A nautical mile is one minture of an arc of lattitude ie 0-60, the
projection is measured in 0-100.<br>
<br>
So does this mean that when I want to draw a line measured in
nautical miles, I have map 0-60 on to 0-100 grid , ie I have to
apply 0.6 factor ?<br>
<br>
So a line starting at lat 1.2 and ending at lat 2.7 becomes a
line 1.12 to 2.42 ?<br>
<br>
regards<br>
<br>
<br>
Dave.<br>
<br>
<br>
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