[postgis-users] degree vs. metric projection performance? - Writing the answer to my own question :)

[Pedro Doria Meunier]

Sorry to trouble you Regina... (blush)

I googled for it. ;-)

sql code:

INSERT INTO spatial_ref_sys (srid,auth_name,auth_srid,srtext,proj4text) 
VALUES
(900913,'EPSG',900913,'PROJCS["Google Mercator", GEOGCS["WGS 
84",DATUM["World Geodetic System 1984", SPHEROID["WGS 84", 6378137.0, 
298.257223563, 
AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich", 
0.0, AUTHORITY["EPSG","8901"]], UNIT["degree", 0.017453292519943295], 
AXIS["Geodetic latitude", NORTH], AXIS["Geodetic longitude", EAST], 
AUTHORITY["EPSG","4326"]], PROJECTION["Mercator (1SP)", 
AUTHORITY["EPSG","9804"]], PARAMETER["semi_major", 6378137.0], 
PARAMETER["semi_minor", 6378137.0], PARAMETER["latitude_of_origin", 
0.0], 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["Easting", EAST], AXIS["Northing", NORTH], 
AUTHORITY["EPSG","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');

BR,
Pedro Doria Meunier

Pedro Doria Meunier wrote:
> Hi Regina :)
>
> Could you please provide the entry for the spatial_ref_sys table for 
> this SRID ?
>
> Best regards,
> Pedro Doria Meunier
>
> Obe, Regina wrote:
>>>  By the way, are the Google Mercator and WGS84 systems equivalent
>>>     
>>
>> No they aren't.  I think Google is a mercator meter projection (not good
>> for measurement though but more or less good for presentation) and they
>> use WGS84 datum when accepting data.  I think it actually has an
>> official SRID (could be wrong)
>> that is EPSG:900913
>>
>> and proj4 looks like this
>>
>> +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
>>
>> People usually plot WGS84 longlat (4326) on Google Maps, thus the
>> confusion.
>>
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