Google maps projections..

[Steve Young]

Hi Dave,
 
Check out John Deck's blogg.
http://johndeck.blogspot.com/2005/09/overlaying-mercator-projected-wms.h
tml
 
Google map's projection is Mercator, but uses lat long as units (rather
than metres). I think there's something that Mapserver does with
bounding boxes that other WMS don't do. I haven't successfully got a WMS
overlaid correctly using my mapserver WMSs (3.6.1 and 4.0). I've got
close using John Deck's method, but suffer tile alignment issues that
don't affect other WMS servers.
 
Might also be worth checking out Mapbuilder. I understand they have a
javascript Mercator/Lat long conversion function. It may be more
accurate than the one John Deck uses.
 
 
Steve
 
 

________________________________

From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Dave Brown
Sent: November 6, 2005 9:38 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: [UMN_MAPSERVER-USERS] Google maps projections..


Could any one help me setting the correct parameters for overlaying my
vector maps (latlong wgs84) over google maps imagery ?
 
I have the right bounds etc.. and when I dont specify the projections at
all, the correct data is overlayed but the projection is off.. 
 
I am experimenting with mapserver as I want to move away from mapxtreme,
which in mapxtreme I used to render the map in mercator projection/Nad27
but whatever I seem to do in mapserver, I get incorrect results..
 
I using OGRINFO on one of my MI .TAB files the projection info is...
 
GEOGCS["unnamed",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563],
        TOWGS84[0,0,0,0,0,0,0]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433]]

 
Any help greatly appreciated. 
 
Thanks,

Dave.


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