[postgis-users] [Fwd: Re: [pgrouting-users] How to join Two points (latitudes and langitudes) in postgis?]

[Stephen Woodbridge]

Your coordinates appear to be lat, lon but in postgis you should be 
using lon, lat. Try fixing that and see if it works.

-Steve

Stephen Woodbridge wrote:
> Please reply to the list so other can benefit from the discussion.
> 
> -------- Original Message --------
> Subject:     Re: [pgrouting-users] How to join Two points (latitudes and
> langitudes) in postgis?
> Date:     Tue, 2 Mar 2010 16:12:48 -0500
> From:     SIDDHESH GANDHI <siddheshgandhi at gmail.com>
> To:     Stephen Woodbridge <woodbri at swoodbridge.com>
> References:
> <5d08242a1003021128q10baab4ci1d7e126e1edec462 at mail.gmail.com>
> <4B8D6A6F.3030208 at swoodbridge.com>
> 
> 
> 
> Thank you for your reply.
> 
> Sorry I thought I am posting in postgis group.
> 
> 1) I didnt get any error message but I didnt get required line when I
> imported required table in QGIS.
> E.g. Suppose I provide latitude and longitude of boston and some other
> city in MA and form a linestring. Now I start QGIS and import this
> linestring from that table. After this I add a vector layer of MA state.
> This should result in generation of linestring from boston to that city,
> but it does not show this.
> 
> If I try to put Points having lattitude and longitude and superimpose it
> on MA state shapefile, I can see points at right location in that 
> shapefile.
> 
> So I was asking if I am wrong in drawing linestring?
> 
> 2) Yes, it is there in database.
> 3) Contraints-
> CONSTRAINT enforce_dims_the_geom CHECK (ndims(the_geom) = 2),
>   CONSTRAINT enforce_geotype_the_geom CHECK (geometrytype(the_geom) =
> 'LINESTRING'::text OR the_geom IS NULL),
>   CONSTRAINT enforce_srid_the_geom CHECK (srid(the_geom) = 4326)
> 
> Can you tell me in short, what do constraints do?
> 
> Thanks Again
> Siddhesh
> 
> 
> On Tue, Mar 2, 2010 at 2:43 PM, Stephen Woodbridge
> <woodbri at swoodbridge.com <mailto:woodbri at swoodbridge.com>> wrote:
> 
>     Siddhesh,
> 
>     This is probably more of a postGIS list query than a pgRouting query.
> 
>     1) you did not say what error messages you might have gotten!
>     2) is the line in the database after you insert it?
>     3) what constraints to you have on the table for SRID?
>     4) you might want to ask on the QGIS list also
> 
>     -Steve
> 
>     SIDDHESH GANDHI wrote:
> 
>         Hi all,
>         I am trying to join 2 points on earth (SRID 4326) by a line but
>         somehow I m not able to see that in QGIS.
> 
>         I have taken some latitudes and longitudes and created points.
>         When I create POINT column and load these points, I can see them
>         on QGIS at exact same locations. (Boston, MA will be at same
>         position where it is now wrt MA state shapefile)
> 
>         Now when i try to join two points (E.g. Boston and Some other
>         place in MA), it does not appear on QGIS.
> 
>         I tried following queries for linestring construction -
>         1) insert into sridline (the_geom) values
>         (ST_setSRID(ST_MakeLine(ST_MakePoint(42.5667212,
>         -70.987212),ST_MakePoint(44.5667212, -70.987212)),4326));
>         Other thing I tried is :
>         2)  insert into sridline (the_geom) values
>         (GeomFromText('Linestring(42.342305 -71.04858,42.278325
>         -70.874176)',4326));
> 
>         For generating POINT :
>         UPDATE sridpoint
>                SET the_geom = ST_SetSRID(ST_Point(
>         longitude,latitude),4326);
> 
>         I can draw linestring when SRID = -1 but with SRID, I am facing
>         problems.
>         Please let me know if someone is aware of how to generate
>         linestring when SRID is specified.
> 
>         Thanks
>         Siddhesh
> 
> 
> 
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