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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | RE: GISList: World Time Zones |
| Date: |
03/09/2002 06:11:06 PM |
| From: |
Dimitri Rotow |
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> Thank you all who have forwarded sources or data for
> the World Time Zones. However, of the many I have
> recieved, none yet have exactly what I need.
> The important aspect of the data is to be able to
> display or view the zone boundary lines themselves on
> the map. Of all the sources found, the map displayes
> the countries with no lines running from the top to
> bottom of the map. I need those lines and the format
> needs to be TAB or SHP so I can bring it in to the
> software and create a .wmf.
> Not asking for much, am I?!?
>
Time zones are not that simple. I was one of the volunteers that helped
prepare the Manifold world time zones map that previous postings referred
you to (and which is the only time zones map in GIS format in the world that
is available for free, unrestricted usage). It is available in .mid/.mif,
.shp and .mfd/.mdb format.
Time zones are often approximated using a graphic that shows the continents
in a cylindrical projection with vertical lines running from the north to
south purporting to show the different zones. However, it's not that
simple: time zones cannot be shown just by a collection of vertical lines
since they are bounded areas that are intermingled with each other.
See http://www.manifold.net/download/freemaps.html for a colored image of
the time zones map. You can see, for example, in Asia how one cannot just
simply draw vertical lines and thus provide accurate time zones.
If lines are what you need, you could take the time zones map (which uses
area objects) and create boundary lines. In Manifold that's a one click
opeation. You would have to use some sensible Transfer Rules to transfer
the attributes to those lines so you could then color them in a sensible,
helpful way.
Cheers,
Dimitri
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