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. <br><br>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.
<br><br><div><span class="gmail_quote">On 7/10/07, <b class="gmail_sendername">Ed McNierney</b> <<a href="mailto:ed@topozone.com">ed@topozone.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Paul -<br><br>Those parameters look good. There is obviously not a "standard" EPSG code<br>for this projection.<br><br>Bradley, you need to decide whether you need to serve these WMS images out<br>to the wide world (
i.e. clients over which you have no control) or only use<br>them "internally" where you can control both your WMS server and the client.<br><br>If it's the former, you have a problem, as there is no EPSG code describing
<br>the projection you need that seems to be in general usage so your clients<br>can be expected to support it. If it's the latter, you're fine. You can<br>simply pick any number you like that's not already taken and add that line
<br>to your EPSG file. It's just a text file. Let's assume you'll pick 41002<br>(since 41001 seems to be in popular usage, but is wrong). Then you'd add<br>the single text line:<br><br><41002>+proj=merc +lat_ts=0 +lon_0=0 +k=
1.0 +x_0=0 +y_0=0 +a=6378137.0<br>+b=6378137.0 +units=m<br><br>To the EPSG files on your server and on each client. Then you can refer to<br>it as SRS=EPSG:41002 in your WMS requests and you're all set.<br><br> - Ed
<br><br>> From: Paul Spencer <<a href="mailto:pspencer@DMSOLUTIONS.CA">pspencer@DMSOLUTIONS.CA</a>><br>> Date: Mon, 9 Jul 2007 14:55:22 -0400<br>> To: Ed McNierney <<a href="mailto:ed@topozone.com">ed@topozone.com
</a>><br>> Cc: "<a href="mailto:MAPSERVER-USERS@LISTS.UMN.EDU">MAPSERVER-USERS@LISTS.UMN.EDU</a>" <<a href="mailto:MAPSERVER-USERS@LISTS.UMN.EDU">MAPSERVER-USERS@LISTS.UMN.EDU</a>><br>> Subject: Re: [UMN_MAPSERVER-DEV] Projections
<br>><br>> Thanks for the clarification Ed (and for fixing the cross-list-<br>> posting-bug :)). I just looked into this more and you are correct (I<br>> was completely wrong). From the site that Bradley quoted, they seem
<br>> to think that the spherical projection is what is used by Google<br>> etc. The (unverified) proj.4 parameters for this seem to be:<br>><br>> +proj=merc +lat_ts=0 +lon_0=0 +k=1.0 +x_0=0 +y_0=0 +a=6378137.0
<br>> +b=6378137.0 +units=m<br>><br>> Cheers<br>><br>> Paul<br>><br>> On 9-Jul-07, at 2:06 PM, Ed McNierney wrote:<br>><br>>> Paul -<br>>><br>>> This doesn't seem correct to me. You're suggesting a Transverse
<br>>> Mercator<br>>> projection on an ellipsoid when the request was for a Mercator on a<br>>> sphere.<br>>><br>>> I did a little Googling around and while it appears that the 41001<br>>> projection is often referred to as "Transverse Mercator", and there
<br>>> are<br>>> several references to the PROJ definition you mention (+proj=tmerc,<br>>> etc.),<br>>> there is a more sensible reference to 41001 being defined in a<br>>> GeoServer<br>>> install as:
<br>>><br>>> PROJCS["WGS84 / Simple Mercator",<br>>> GEOGCS["WGS 84",<br>>> DATUM["WGS_1984",<br>>> SPHEROID["WGS_1984", 6378137.0, 298.257223563
]],<br>>> PRIMEM["Greenwich", 0.0],<br>>> UNIT["degree", 0.017453292519943295],<br>>> AXIS["Lon", EAST],<br>>> AXIS["Lat", NORTH]],<br>>> PROJECTION["Mercator_1SP"],
<br>>> PARAMETER["central_meridian", 0.0],<br>>> PARAMETER["scale_factor", 1.0],<br>>> PARAMETER["false_easting", 0.0],<br>>> PARAMETER["false_northing",
0.0],<br>>> UNIT["m", 1.0],<br>>> AXIS["x", EAST],<br>>> AXIS["y", NORTH],<br>>> AUTHORITY["EPSG","41001"]]<br>>><br>>> This is more sensible (at least it's a Mercator projection!) but it
<br>>> is still<br>>> a ellipsoidal rather than spherical projection, so it's not quite<br>>> right.<br>>><br>>> However, the entire universe of Web-based "geographic" projection
<br>>> fans,<br>>> stimulated by Google and Microsoft, obviously don't really get<br>>> bothered when<br>>> their maps are "not quite right", so I should learn not to be so<br>>> fussy.
<br>>><br>>> - Ed<br>>><br>>> P.S. I modified the reply to go only to the MAPSERVER-USERS list,<br>>> since the<br>>> original cross-posting to both lists only complicates matters for
<br>>> people<br>>> trying to help.<br>>><br>>><br>>>> From: Paul Spencer <<a href="mailto:pspencer@DMSOLUTIONS.CA">pspencer@DMSOLUTIONS.CA</a>><br>>>> Reply-To: Paul Spencer <
<a href="mailto:pspencer@DMSOLUTIONS.CA">pspencer@DMSOLUTIONS.CA</a>><br>>>> Date: Sun, 8 Jul 2007 22:17:03 -0400<br>>>> To: <<a href="mailto:MAPSERVER-DEV@LISTS.UMN.EDU">MAPSERVER-DEV@LISTS.UMN.EDU
</a>><br>>>> Subject: Re: [UMN_MAPSERVER-DEV] Projections<br>>>><br>>>> You need what is commonly referred to as EPSG:41001, defined as:<br>>>><br>>>> <41001> +proj=tmerc +ellps=WGS84 +units=m +no_defs <>
<br>>>><br>>>> To use this, add the above line to your 'epsg' file and also add a<br>>>> projection object to your map object:<br>>>><br>>>> PROJECTION<br>>>> "init=epsg:41001"
<br>>>> END<br>>>><br>>>> You will also need to make sure that every layer in your map file has<br>>>> a proper projection so mapserver can reproject it correctly.<br>>>><br>>>> Cheers
<br>>>><br>>>> Paul<br>>>><br>>>> On 8-Jul-07, at 9:44 PM, Bradley Mclain wrote:<br>>>><br>>>>> This is kind of hard to explain but what I want to do is use<br>>>>> Mapserver to project my data which is in the GDA94 projection as
<br>>>>> shown below:<br>>>>><br>>>>> "# GDA94 / MGA zone 55<br>>>>> <28355> +proj=utm +zone=55 +south +ellps=GRS80<br>>>>> +towgs84=0,0,0,0,0,0,0 +units=m +no_defs <>"
<br>>>>><br>>>>> to a projection that will be able to be properly merged with Google<br>>>>> maps (using OpenLayers) which uses a projection something like the<br>>>>> following:
<br>>>>><br>>>>> "Update 4: Agreement frrom Melita Kennedy and David Burrows that<br>>>>> Google Maps and Virtual Earth use spherical equations for the<br>>>>> Mercator projection. The correct proj4 settings are:
<br>>>>><br>>>>> +proj=merc +latts=0 +lon0=0 +k=1.0 +x0=0 +y0=0<br>>>>> +a=6378137.0 +b=6378137.0 +units=m<br>>>>><br>>>>> Note this is different than using the ellipsoidal equations which
<br>>>>> would be:<br>>>>><br>>>>> +proj=merc +latts=0 +lon0=0 +k=1.0 +x0=0 +y0=0<br>>>>> +ellps=WGS84 +datum=WGS84 +units=m no_defs"<br>>>>><br>>>>> I believe that I need to use Mapserver to do this but I have no
<br>>>>> idea how to go about it. Currently my Mapserver is running fine<br>>>>> displaying the data correctly using the GDA94 projection except i<br>>>>> had to use a .vrt file to correctly align the raster image which
<br>>>>> was slightly out of alignment. I have also set up and can call my<br>>>>> Mapserver as a WMS (thought having issues with the WMS Layer<br>>>>> function in OpenLayers, just displays a white screen but I believe
<br>>>>> that this is to do with projections)<br>>>>><br>>>>> My Mapserver has been compiled with GD, GDAL, GEOS, PostGIS, PHP<br>>>>> and proj4.<br>>>>><br>>>>> In my mapfile I have defined each layer using "init=epsg:28355" as
<br>>>>> well as globally defining the map using the same projection.<br>>>>><br>>>>> This reason I am trying to do this is because currently I don't<br>>>>> think that my projection can be properly imported into OpenLayers
<br>>>>> and merged with Google Maps.<br>>>>><br>>>>> Thanks<br>>>>><br>>>>> Brad<br>>>><br>>>> +-----------------------------------------------------------------+
<br>>>> |Paul Spencer <a href="mailto:pspencer@dmsolutions.ca">pspencer@dmsolutions.ca</a> |<br>>>> +-----------------------------------------------------------------+<br>>>> |Chief Technology Officer |
<br>>>> |DM Solutions Group Inc <a href="http://www.dmsolutions.ca/">http://www.dmsolutions.ca/</a> |<br>>>> +-----------------------------------------------------------------+<br>>>
<br>><br>> +-----------------------------------------------------------------+<br>> |Paul Spencer <a href="mailto:pspencer@dmsolutions.ca">pspencer@dmsolutions.ca</a> |<br>> +-----------------------------------------------------------------+
<br>> |Chief Technology Officer |<br>> |DM Solutions Group Inc <a href="http://www.dmsolutions.ca/">http://www.dmsolutions.ca/</a> |<br>> +-----------------------------------------------------------------+
<br>><br>><br>><br>><br>><br></blockquote></div><br>