[postgis-users] Absolute Beginner

[Dave Potts]

Bob Pawley wrote:

I suspect your not using the latest version of postgis.  The command 
select postgis_version(); will return which version use are using.

D.
> Thanks Regina
>
> My version of PostgreSQL has no functions that start with ST_ such as 
> ST_GeomFromText.
>
> I removed the ST_ from the code you suggested making it GeomFromText 
> and it worked well.
>
> What does the ST_ signify??
>
> Bob
> ----- Original Message ----- From: "Obe, Regina" 
> <robe.dnd at cityofboston.gov>
> To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
> Sent: Tuesday, April 22, 2008 5:21 AM
> Subject: RE: [postgis-users] Absolute Beginner
>
>
> Bob,
>
> Unfortunately I'm not too familiar with Delphi (aside from its some
> Pascal derivative) and I guess no one is in this group since no one
> responded to your question.
>
> I guess it depends what Delphi is expecting for the Canvas - e.g. can it
> use SVG maybe or most unlikely (WKT  or WKB representations).  At
> anyrate I suspect you are more likely to find Delphi plugins for
> rendering SVG than any other format output by PostGIS.
>
> If you can find SVG plugins, there is an asSVG function in PostGIS that
> may prove useful to you.
>
> As far as storing the path, you could put it in your database as a
> LINESTRING of the form
>
> INSERT INTO temppath(fieldname)
> VALUES(ST_GeomFromText('LINESTRING(1 2,3 12)'))
>
> You can ignore use of SRID since you don't care about Geography.
>
> Then query it as SVG format with
>
> SELECT AsSVG(fieldname)
> FROM temppath
>
> or expand it out to x and y with something like
>
> SELECT somekeyfield, ST_x(the_geom) as x, ST_y(the_geom) as y
> FROM
> (SELECT somekeyfield, ST_PointN(fieldname, generate_series(1,
> ST_numpoints(fieldname)) As the_geom
> FROM temppath)  as foo
>
> That will give you the x and y coordinates of each point of the line
> string (with all belonging to the same linestring having
> the same somekeyfield
>
> and then you can just plot the x and y on canvas.
>
> Hope that helps,
> Regina
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Bob
> Pawley
> Sent: Monday, April 21, 2008 1:25 PM
> To: PostGIS Users Discussion
> Subject: [postgis-users] Absolute Beginner
>
> I know that most, if not all, on this list are interested in the
> geography
> side of GIS.
>
> However, I have a question on the geometry side.
>
> I have a Delphi Canvas that I need to connect to a PostgreSQL database.
>
> What is the minimum table structure that is needed to hold the vector
> coordinates such as this path ((1,2), (3, 12)) so that it will draw the
> line
> in Delphi?
>
> Perhaps the Delphi knowledgeable people can let me know if the following
> query is any where near correct to accomplish this action.
>
> Thanks in advance.
>
> Bob
>     PSQLQuery1.Close;
>      PSQLQuery1.SQL.Clear;
>      PSQLQuery1.SQL.Add ('Select * fieldname ');
>      PSQLQuery1.SQL.Add ('FROM temppath');
>      PSQLQuery1.Prepare;
>      PSQLQuery1.Open;
>      PSQLQuery1.First ;
>      i2:= PSQLQuery1.FieldByName('fieldname').AsInteger ;
>      testfrm:= IntToStr(i2);
>
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