I want to provide a geometry that was input from Google Maps (SRID 3857)
for GPS units (SRID 4326). How should I do that?

 

I hated to post this, frankly. I know it's a "thinko;" I'm not
understanding the concept. If I describe a geometry in SRID 3857, then
it seems to me that that point would have a slightly different
description in SRID 4326. Instead, they're wildly different. So, I know
I am misunderstanding in some basic way. 

 

Ron

 

________________________________

From: [email protected]
[mailto:[email protected]] On Behalf Of
Emilie Laffray
Sent: Thursday, May 20, 2010 12:48 PM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] I can't make sense of this.

 

Why would you expect them to be similar? There are different sets of
coordinates.
Your first set of coordinates looks like wgs84 but you set the srid to
Google srid. 
It doesn't make sense.

        On 20 May 2010 17:38, "Ronald Phillips"
<[email protected]> wrote:

        SELECT   

                    ST_AsText(

                                ST_GeomFromText('POINT(-81.064544
40.28787)', 3857)

                                ) 

        AS goog, 

                    ST_AsText(

                                ST_Transform(

        
ST_GeomFromText('POINT(-81.064544 40.28787)', 3857)

                                , 4326)

                    ) 

        AS gcs

         

        3857 is "Google's" SRID, and 4326 is a fairly standard GPS SRID.
I'm getting this:

         

        Goog: "POINT(-81.064544 40.28787)";

        Gcs: "POINT(-0.000728215188753794 0.000361912093851508)"

         

        What am I doing wrong, that they're so different?

         

        Ronald Phillips, B.S., M.S.

        Programmer/Analyst

         

        Summit County Engineer

        538 E. South St.

        Akron OH 44311

        330.643.8061

        http://www.linkedin.com/in/rwphillips

         

        
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