[Mapserver-users] Can't seem to get the projection correct
Ed McNierney
ed at topozone.com
Tue Feb 18 17:29:13 EST 2003
Make sure your UNITS are correct. They probably were DD, and probably
should be METERS.
- Ed
Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA 01863
Phone: (978) 251-4242 Fax: (978) 251-1396
ed at topozone.com
-----Original Message-----
From: Martin, Daniel [mailto:DMartin at erac.com]
Sent: Tuesday, February 18, 2003 5:11 PM
To: Ed McNierney; mapserver-users at lists.gis.umn.edu
Subject: RE: [Mapserver-users] Can't seem to get the projection correct
Wow, yes! That's the key I hadn't yet tried, proj=merc. Hadn't tried
because I've never seen it before in any of the PROJ definitions.
The result is definitely what I was looking for. Everything looks
perfect
except my scalebar is now doing some CRAZY stuff. Does reprojection
ruin
the scalebar? I've attached two examples.
Thanks so much,
Dan
> -----Original Message-----
> From: Ed McNierney [mailto:ed at topozone.com]
> Sent: Tuesday, February 18, 2003 3:56 PM
> To: Martin, Daniel; mapserver-users at lists.gis.umn.edu
> Subject: RE: [Mapserver-users] Can't seem to get the
> projection correct
>
>
> Dan -
>
> Use merc, not tmerc. Tmerc is the Transverse Mercator, which
> (although
> it's more popular) is not what you want.
>
> - Ed
>
> Ed McNierney
> President and Chief Mapmaker
> TopoZone.com / Maps a la carte, Inc.
> 73 Princeton Street, Suite 305
> North Chelmsford, MA 01863
> Phone: (978) 251-4242 Fax: (978) 251-1396
> ed at topozone.com
>
>
> -----Original Message-----
> From: Martin, Daniel [mailto:DMartin at erac.com]
> Sent: Tuesday, February 18, 2003 4:43 PM
> To: mapserver-users at lists.gis.umn.edu
> Subject: RE: [Mapserver-users] Can't seem to get the
> projection correct
>
> Thanks Ed, I'm tinkering with Mercator now (or at least I think I am).
> Not
> having much luck actually - but I think you are right. I'm just not
> very
> experienced with projections, so working with them is a
> matter of trial
> and
> error for me. I'm assuming you mean Mercator as in proj=tmerc not
> proj=utm,
> though I wouldn't know better either way. I've basically been trying
> options from the PROJ list,
> http://mapserver.gis.umn.edu/doc36/proj.html
>
> Most of the time I end up with an error, a blank map, or a map that
> looks
> like a rolled newspaper. I'll get it right eventually.
>
> Thanks again,
> Dan
>
>
>
> > -----Original Message-----
> > From: Ed McNierney [mailto:ed at topozone.com]
> > Sent: Tuesday, February 18, 2003 2:49 PM
> > To: Martin, Daniel; mapserver-users at lists.gis.umn.edu
> > Subject: RE: [Mapserver-users] Can't seem to get the
> > projection correct
> >
> >
> > Daniel -
> >
> > As I mentioned before, you are probably accustomed to seeing
> > maps in the
> > Mercator projection. Rather than fiddling with the image size, you
> > might want to look into having MapServer generate Mercator output
> > images.
> >
> > The Mercator projection stretches the Y-dimension as compared to the
> > geographic projection. The distance between parallels of latitude
> > increases as you move away from the equator. At a
> > Missouri-ish latitude
> > of 40 degrees North, one degree of latitude is 1.414 times
> taller in a
> > Mercator projection than in a geographic projection. This
> would mean
> > that if your horizontal (longitude) scale were, say, 7 pixels per
> > degree, you would expect your vertical (latitude) scale to be
> > 7 * 1.414
> > = 9.9 pixels per degree.
> >
> > Since this happens to be exactly what we see in the MapInfo
> image you
> > sent (which is roughly centered on Missouri), I think it's
> > pretty likely
> > that both your memory and your MapInfo maps are in the Mercator
> > projection. If you set up MapServer to create Mercator
> > output images I
> > suspect you'll match your MapInfo results without having to
> fudge the
> > image size (which isn't really correct anyway because the
> > vertical scale
> > distortion is nonlinear and varies with the latitude).
> >
> > - Ed
> >
> > Ed McNierney
> > President and Chief Mapmaker
> > TopoZone.com / Maps a la carte, Inc.
> > 73 Princeton Street, Suite 305
> > North Chelmsford, MA 01863
> > Phone: (978) 251-4242 Fax: (978) 251-1396
> > ed at topozone.com
> >
> >
> > -----Original Message-----
> > From: Martin, Daniel [mailto:DMartin at erac.com]
> > Sent: Tuesday, February 18, 2003 3:17 PM
> > To: mapserver-users at lists.gis.umn.edu
> > Subject: RE: [Mapserver-users] Can't seem to get the
> > projection correct
> >
> > I want to thank everyone for all the responses.
> >
> > Daniel Morissette hit the nail on the head. MapInfo and
> Mapquest are
> > indeed
> > doing some matter of x-scale adjustment to make maps "look
> better".
> >
> > I know this isn't scientific, but my maps in MapInfo look
> > like I expect
> > them
> > too. For instance, my home state of Missouri that I've seen on maps
> > thousands of times "looks" like I know it to look in MapInfo. In
> > MapServer
> > it "looks squished". I don't know how to express it any
> > different than
> > that. One way I've adjusted for it is to force a new
> aspect ratio in
> > the
> > <img > tag on the HTML template to "squish" the image back.
> > But I hate
> > that
> > solution. It's not a good solution in my book.
> >
> > I'm going to take a look into some things mentioned and see
> > if I can get
> > anywhere. I'll be sure to let you know how they turn out.
> >
> > Thanks again,
> > Dan Martin
> >
> >
> >
> > > -----Original Message-----
> > > From: Daniel Morissette [mailto:morissette at dmsolutions.ca]
> > > Sent: Tuesday, February 18, 2003 12:10 PM
> > > To: Martin, Daniel
> > > Cc: mapserver-users at lists.gis.umn.edu
> > > Subject: Re: [Mapserver-users] Can't seem to get the
> > > projection correct
> > >
> > >
> > > "Martin, Daniel" wrote:
> > > >
> > > > Sorry to correct you, but that's not true - at least not
> > > since I've worked
> > > > with MapInfo (version 5 through 7). That may be an optional
> > > configuration,
> > > > but by default MapInfo doesn't change the aspect ratio of
> > > the data with the
> > > > window. By default, the data's horizontal extent stays the
> > > same as the
> > > > window is resized, but the vertical changes to maintain the
> > > projection.
> > > >
> > >
> > > You're correct, I was wrong on that, I should have
> checked first. I
> > > found the option that's causing this effect... open your
> > lat/lon map,
> > > then select Map/Options, the "Distance/Area Using:" radio box
> > > is set to
> > > Spherical. Change the projection to "Non-Earth", and the
> > > "Distance/Area" will switch to cartesian, and then your map
> > will look
> > > exactly as it does in MapServer.
> > >
> > > I'm not sure what this spherical distance option does
> exactly but it
> > > seems that MapInfo (and MapQuest) use this to adjust the
> > > x-scale of the
> > > map to make it look better, that's why the map looks
> > > different, this is
> > > not a projection effect, it's a map scaling effect.
> > Unfortunately at
> > > this point MapServer supports only maps with x-scale ==
> y-scale (or
> > > square pixels if you like) so you won't be able to reproduce
> > > that unless
> > > you can define a projection that produces a similar effect.
> > >
> > > --
> > > ------------------------------------------------------------
> > > Daniel Morissette morissette at dmsolutions.ca
> > > DM Solutions Group http://www.dmsolutions.ca/
> > > ------------------------------------------------------------
> > >
> > _______________________________________________
> > Mapserver-users mailing list
> > Mapserver-users at lists.gis.umn.edu
> > http://lists.gis.umn.edu/mailman/listinfo/mapserver-users
> >
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