data (#23) - Probable explanation for this? (#320) - Message List

Probable explanation for this?

Hi Everyone

I am trying to overlay data ( onto Google Maps. I have downloaded data from Canadian website as recommended by a tutorial on this website. I have changed SRID to 54004 for Victoria table. But when I display Victoria table on Google Maps then it appears smaller than Google Maps (nearly half of the size of area on Google Map). When I try to use 900913 for Victoria table it does not appear at all.

I am using OpenLayers? and my map projection is in 900913.

The Victoria tables is published as a WMS, thus I am using 900913 project for it in the mapfile.

Here is my ESPG entry for Proj4 (for MapServer)

<900913> +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs

Here is the insert statement for 900913 for PostGIS (it is taken from this website as well)

INSERT INTO spatial_ref_sys (srid, auth_name, auth_srid, srtext, proj4text) VALUES (900913, 'EPSG', 900913, 'PROJCS["unnamed",GEOGCS["unnamed ellipse",DATUM["unknown",SPHEROID["unnamed",6378137,0]], PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]], PROJECTIONMercator_2SP?,PARAMETER["standard_parallel_1",0],PARAMETER["central_meridian",0],PARAMETER["false_easting",0], PARAMETER["false_northing",0],UNIT["Meter",1],EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs"]]',

'+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs');

Could any one help me in understating what is wrong? Will it overlay properly that is the best.


  • Message #1274

    Which version of OpenLayers? do you use?

    • Message #1285

      Hi Daniel

      I am using OpenLayers? 2.8

      Thanks for reply.

      • Message #1287

        I'm not sure about the details anymore. But at the time, when I made this workshop (for the FOSS4G conference in 2007), the vector support of OpenLayers? was still in heavy development and I had to take a sandbox version to get Google Maps and vectors together.

        That time there was no 900913 projection either and 54004 was the one most people used. I remember that I had drifts like you have now, too. But only on higher scales. It seems to me now, that somewhere a 54004 projection is still "alive" in your application. I just have no good advice where it could be.

        There were some other issues with the 2007 workshop and newer versions of OpenLayers?, because a lot of things changed since then. Did you take a look at these wiki pages with a few modifications: