Just thought I let you all know I have managed to get it working, all I
needed to do was convert the co-ordinates to get the new extent using proj,
now everything lines up perfect and works beautifully.
Thanks for all your help guys :)
On 7/10/07, Bradley Mclain <[EMAIL PROTECTED]> wrote:
>
> Any tips on how to do this? I've looked through0 the proj manual but I'm
> a bit unsure how to go about it.
>
> On 7/10/07, Ed McNierney < [EMAIL PROTECTED]> wrote:
> >
> > Bradley –
> >
> >
> >
> > BBOX is a required WMS parameter, so you must be using it.
> >
> >
> >
> > You have to be able to express the geographic extents of your area of
> > interest in the units used by your desired map projection. Otherwise
> > there's no way you can know what you're asking for. I don't use OpenLayers
> > and can't help you on its configuration, but you can use the PROJ
> > command-line tools to reproject individual coordinate pairs from your input
> > to your output projections so you can calculate a starting bounding box for
> > your map.
> >
> >
> >
> > - Ed
> >
> >
> >
> > *From:* Bradley Mclain [mailto:[EMAIL PROTECTED]
> > *Sent:* Monday, July 09, 2007 10:11 PM
> > *To:* Ed McNierney
> > *Cc:* [EMAIL PROTECTED]
> > *Subject:* Re: [UMN_MAPSERVER-USERS] [UMN_MAPSERVER-DEV] Projections
> >
> >
> >
> > Being defined by server and clients at the moment shouldn't be an
> > issue because I am testing off the server at the moment which I have updated
> > the proj epsg file. Is this correct have I correctly understood this
> > concept?
> >
> > How do I get the correct extent for this new projection I have
> > absolutely now idea how to do it? I'm not using bbox so this shouldn't be a
> > problem.
> >
> > On 7/10/07, *Ed McNierney* <[EMAIL PROTECTED]> wrote:
> >
> > Bradley –
> >
> >
> >
> > Don't just experiment with combinatorial testing – think about what
> > you're trying to do, make sure you understand it, then be sure your map file
> > and request do it. Since we've explained that whatever EPSG code you're
> > using is not standard, you need to be sure that it is defined in both the
> > server and all clients. Have you done that? Failure to do so would be an
> > obvious cause of an "SRS error" from the client.
> >
> >
> >
> > Remember that when you change your map file output or your WMS request
> > to a different SRS, you need to change the extent or BBOX parameters, too.
> > In a WMS request the BBOX parameter always uses the units of the SRS used,
> > so you can't just keep the same GDA94 coordinates and expect them to work.
> > If you don't change them, you're requesting a Mercator output image at some
> > random location that bears no relation to your input data, so it is quite
> > likely to give you a white image (since no input data overlaps the requested
> > map area).
> >
> >
> >
> > - Ed
> >
> >
> >
> > *From:* UMN MapServer Users List [mailto:[EMAIL PROTECTED]
> > *On Behalf Of *Bradley Mclain
> > *Sent:* Monday, July 09, 2007 9:12 PM
> > *To:* [EMAIL PROTECTED]
> > *Subject:* Re: [UMN_MAPSERVER-USERS] [UMN_MAPSERVER-DEV] Projections
> >
> >
> >
> > When I have the custom projection defined in my mapfile and the native
> > projection defined for layers the map does not show up when doing a WMS
> > getmap request, it just appears white.
> >
> > When I change it so that all layers have the custom projection, the
> > map displays correctly from a WMS request but fails to display correctly in
> > OpenLayers giving an SRS error.
> >
> > On 7/10/07, *Ed McNierney* <[EMAIL PROTECTED]> wrote:
> >
> > Paul -
> >
> > Those parameters look good. There is obviously not a "standard" EPSG
> > code
> > for this projection.
> >
> > Bradley, you need to decide whether you need to serve these WMS images
> > out
> > to the wide world ( i.e. clients over which you have no control) or
> > only use
> > them "internally" where you can control both your WMS server and the
> > client.
> >
> > If it's the former, you have a problem, as there is no EPSG code
> > describing
> > the projection you need that seems to be in general usage so your
> > clients
> > can be expected to support it. If it's the latter, you're fine. You
> > can
> > simply pick any number you like that's not already taken and add that
> > line
> > to your EPSG file. It's just a text file. Let's assume you'll pick
> > 41002
> > (since 41001 seems to be in popular usage, but is wrong). Then you'd
> > add
> > the single text line:
> >
> > <41002>+proj=merc +lat_ts=0 +lon_0=0 +k= 1.0 +x_0=0 +y_0=0 +a=
> > 6378137.0
> > +b=6378137.0 +units=m
> >
> > To the EPSG files on your server and on each client. Then you can
> > refer to
> > it as SRS=EPSG:41002 in your WMS requests and you're all set.
> >
> > - Ed
> >
> > > From: Paul Spencer <[EMAIL PROTECTED]>
> > > Date: Mon, 9 Jul 2007 14:55:22 -0400
> > > To: Ed McNierney <[EMAIL PROTECTED] >
> > > Cc: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> > > Subject: Re: [UMN_MAPSERVER-DEV] Projections
> > >
> > > Thanks for the clarification Ed (and for fixing the cross-list-
> > > posting-bug :)). I just looked into this more and you are correct
> > (I
> > > was completely wrong). From the site that Bradley quoted, they seem
> >
> > > to think that the spherical projection is what is used by Google
> > > etc. The (unverified) proj.4 parameters for this seem to be:
> > >
> > > +proj=merc +lat_ts=0 +lon_0=0 +k=1.0 +x_0=0 +y_0=0 +a=6378137.0
> > > +b=6378137.0 +units=m
> > >
> > > Cheers
> > >
> > > Paul
> > >
> > > On 9-Jul-07, at 2:06 PM, Ed McNierney wrote:
> > >
> > >> Paul -
> > >>
> > >> This doesn't seem correct to me. You're suggesting a Transverse
> > >> Mercator
> > >> projection on an ellipsoid when the request was for a Mercator on a
> > >> sphere.
> > >>
> > >> I did a little Googling around and while it appears that the 41001
> > >> projection is often referred to as "Transverse Mercator", and there
> >
> > >> are
> > >> several references to the PROJ definition you mention (+proj=tmerc,
> > >> etc.),
> > >> there is a more sensible reference to 41001 being defined in a
> > >> GeoServer
> > >> install as:
> > >>
> > >> PROJCS["WGS84 / Simple Mercator",
> > >> GEOGCS["WGS 84",
> > >> DATUM["WGS_1984",
> > >> SPHEROID["WGS_1984", 6378137.0, 298.257223563 ]],
> > >> PRIMEM["Greenwich", 0.0],
> > >> UNIT["degree", 0.017453292519943295],
> > >> AXIS["Lon", EAST],
> > >> AXIS["Lat", NORTH]],
> > >> PROJECTION["Mercator_1SP"],
> > >> PARAMETER["central_meridian", 0.0],
> > >> PARAMETER["scale_factor", 1.0],
> > >> PARAMETER["false_easting", 0.0],
> > >> PARAMETER["false_northing", 0.0],
> > >> UNIT["m", 1.0],
> > >> AXIS["x", EAST],
> > >> AXIS["y", NORTH],
> > >> AUTHORITY["EPSG","41001"]]
> > >>
> > >> This is more sensible (at least it's a Mercator projection!) but it
> >
> > >> is still
> > >> a ellipsoidal rather than spherical projection, so it's not quite
> > >> right.
> > >>
> > >> However, the entire universe of Web-based "geographic" projection
> > >> fans,
> > >> stimulated by Google and Microsoft, obviously don't really get
> > >> bothered when
> > >> their maps are "not quite right", so I should learn not to be so
> > >> fussy.
> > >>
> > >> - Ed
> > >>
> > >> P.S. I modified the reply to go only to the MAPSERVER-USERS list,
> > >> since the
> > >> original cross-posting to both lists only complicates matters for
> > >> people
> > >> trying to help.
> > >>
> > >>
> > >>> From: Paul Spencer <[EMAIL PROTECTED]>
> > >>> Reply-To: Paul Spencer < [EMAIL PROTECTED]>
> > >>> Date: Sun, 8 Jul 2007 22:17:03 -0400
> > >>> To: <[EMAIL PROTECTED] >
> > >>> Subject: Re: [UMN_MAPSERVER-DEV] Projections
> > >>>
> > >>> You need what is commonly referred to as EPSG:41001, defined as:
> > >>>
> > >>> <41001> +proj=tmerc +ellps=WGS84 +units=m +no_defs <>
> > >>>
> > >>> To use this, add the above line to your 'epsg' file and also add a
> > >>> projection object to your map object:
> > >>>
> > >>> PROJECTION
> > >>> "init=epsg:41001"
> > >>> END
> > >>>
> > >>> You will also need to make sure that every layer in your map file
> > has
> > >>> a proper projection so mapserver can reproject it correctly.
> > >>>
> > >>> Cheers
> > >>>
> > >>> Paul
> > >>>
> > >>> On 8-Jul-07, at 9:44 PM, Bradley Mclain wrote:
> > >>>
> > >>>> This is kind of hard to explain but what I want to do is use
> > >>>> Mapserver to project my data which is in the GDA94 projection as
> > >>>> shown below:
> > >>>>
> > >>>> "# GDA94 / MGA zone 55
> > >>>> <28355> +proj=utm +zone=55 +south +ellps=GRS80
> > >>>> +towgs84=0,0,0,0,0,0,0 +units=m +no_defs <>"
> > >>>>
> > >>>> to a projection that will be able to be properly merged with
> > Google
> > >>>> maps (using OpenLayers) which uses a projection something like
> > the
> > >>>> following:
> > >>>>
> > >>>> "Update 4: Agreement frrom Melita Kennedy and David Burrows that
> > >>>> Google Maps and Virtual Earth use spherical equations for the
> > >>>> Mercator projection. The correct proj4 settings are:
> > >>>>
> > >>>> +proj=merc +latts=0 +lon0=0 +k=1.0 +x0=0 +y0=0
> > >>>> +a=6378137.0 +b=6378137.0 +units=m
> > >>>>
> > >>>> Note this is different than using the ellipsoidal equations
> > which
> > >>>> would be:
> > >>>>
> > >>>> +proj=merc +latts=0 +lon0=0 +k=1.0 +x0=0 +y0=0
> > >>>> +ellps=WGS84 +datum=WGS84 +units=m no_defs"
> > >>>>
> > >>>> I believe that I need to use Mapserver to do this but I have no
> > >>>> idea how to go about it. Currently my Mapserver is running fine
> > >>>> displaying the data correctly using the GDA94 projection except i
> > >>>> had to use a .vrt file to correctly align the raster image which
> > >>>> was slightly out of alignment. I have also set up and can call my
> > >>>> Mapserver as a WMS (thought having issues with the WMS Layer
> > >>>> function in OpenLayers, just displays a white screen but I
> > believe
> > >>>> that this is to do with projections)
> > >>>>
> > >>>> My Mapserver has been compiled with GD, GDAL, GEOS, PostGIS, PHP
> > >>>> and proj4.
> > >>>>
> > >>>> In my mapfile I have defined each layer using "init=epsg:28355"
> > as
> > >>>> well as globally defining the map using the same projection.
> > >>>>
> > >>>> This reason I am trying to do this is because currently I don't
> > >>>> think that my projection can be properly imported into OpenLayers
> >
> > >>>> and merged with Google Maps.
> > >>>>
> > >>>> Thanks
> > >>>>
> > >>>> Brad
> > >>>
> > >>>
> > +-----------------------------------------------------------------+
> > >>> |Paul Spencer [EMAIL PROTECTED]
> > |
> > >>>
> > +-----------------------------------------------------------------+
> > >>> |Chief Technology Officer
> > |
> > >>> |DM Solutions Group Inc http://www.dmsolutions.ca/|
> > >>>
> > +-----------------------------------------------------------------+
> > >>
> > >
> > > +-----------------------------------------------------------------+
> > > |Paul Spencer [EMAIL PROTECTED] |
> > > +-----------------------------------------------------------------+
> > > |Chief Technology Officer |
> > > |DM Solutions Group Inc http://www.dmsolutions.ca/ |
> > > +-----------------------------------------------------------------+
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
> >
> >
>
>
