[postgis-users] Spheroid Question

[Stephen Woodbridge]

Dan,

I am be wrong on my understanding, but it looks like you might be doing 
a full table scan. Since SRID:4326 is in decimal degrees, and you are 
expanding you point by +-2000 decimal degrees which is likely 
overlapping every object in the table. If you want to select items in 
2km of your point you might want to convert 2000 into its approximate 
degrees for the && clause.

Also what units do the *_spheroid() return in?

-Steve W.

Dan Phillips wrote:
> Okay, this works. It's just really slow (~40 minutes). Any suggestions on
> speeding this up?
> 
> SELECT
>   CRID,
>   distance_spheroid(centroid(the_geom),
>   setSRID(makepoint(-72.607912, 42.058052),4326),
>   'SPHEROID["GRS_1980",6378137,298.257222101]') as distance
> FROM crrts
> WHERE
>   the_geom && expand(setSRID(makepoint(-72.607912, 42.058052),4326),2000)
>   AND distance_spheroid(centroid(the_geom),
>   setSRID(makepoint(-72.607912, 42.058052),4326),
>   'SPHEROID["GRS_1980",6378137,298.257222101]')<2000 ;
> 
> Thanks,
> 
> Dan
> 
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net]On Behalf Of
> strk at refractions.net
> Sent: Friday, June 24, 2005 11:39 AM
> To: PostGIS Users Discussion
> Subject: Re: [postgis-users] Spheroid Question
> 
> 
> On Fri, Jun 24, 2005 at 11:36:27AM -0400, Dan Phillips wrote:
> 
>>Thanks Jeff & Paul. That was the problem.
>>
>>Now I'm getting "ERROR:  Operation on two geometries with different SRIDs"
>>
>>I assume this is because I'm not setting the SRID for my makepoint(). How
> 
> do
> 
>>I do this to make it match the SRID (4326) of my 'crrts' table?
> 
> 
> Use the setSRID() function:
> setSRID(makepoint())
> --strk;
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