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Re: Maps - ellipsoids in map_set ('scale on the central meridian') [message #87227 is a reply to message #87223]

Thu, 16 January 2014 14:14

Andy Sayer
Messages: 127
Registered: February 2009

Senior Member

Actually I was adding the continental outlines after mapping with map_continents (and using /hires and /coast) rather than during map_set.

I experimented a bit with different ellipsoids (guessing 1 and 0.9996 for this mysterious third parameter) but it didn't seem to make a visible difference. So either I am doing it wrong (possible), or the difference between Clarke and WGS 84 ellipsoids is smaller than one data pixel (~100 m).

I'm planning to try the GSHHS stuff in the morning... we will see! But I would really not expect that would make such a difference (~1-2 km mismatch). Then again as the IDL maps don't recognise some countries which have existed for over a decade now, perhaps I should not be surprised. ;)

Andy

On Thursday, January 16, 2014 4:09:19 PM UTC-5, David Fanning wrote:
> AMS writes:
>
>
>
>> I suspected you might say that, David!
>
>
>
> Well, aside from MAP_SET just being generally terrible for doing
>
> professional map projection stuff, are you sure you are using the HI-RES
>
> continental outlines? Is this the kind of thing that can be improved
>
> with the GSHHS data?
>
>
>
> Cheers,
>
>
>
> David
>
> --
>
> David Fanning, Ph.D.
>
> Fanning Software Consulting, Inc.
>
> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
>
> Sepore ma de ni thue. ("Perhaps thou speakest truth.")

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[Message index]

		Maps - ellipsoids in map_set ('scale on the central meridian') By: Andy Sayer on Thu, 16 January 2014 10:58
		Re: Maps - ellipsoids in map_set ('scale on the central meridian') By: David Fanning on Thu, 16 January 2014 11:01
		Re: Maps - ellipsoids in map_set ('scale on the central meridian') By: Andy Sayer on Thu, 16 January 2014 12:28
		Re: Maps - ellipsoids in map_set ('scale on the central meridian') By: David Fanning on Thu, 16 January 2014 13:09
		Re: Maps - ellipsoids in map_set ('scale on the central meridian') By: David Fanning on Thu, 16 January 2014 13:24
		Re: Maps - ellipsoids in map_set ('scale on the central meridian') By: Andy Sayer on Thu, 16 January 2014 14:14
		Re: Maps - ellipsoids in map_set ('scale on the central meridian') By: Andy Sayer on Fri, 17 January 2014 06:34

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