Thanks Andy and Greg for the clarification, Sorry for being so dense.
So I take it sprintf would never ever do any rounding (they merely print % significant digits). So g and f always truncate but g can flip to scientific if < .001 http://www.cplusplus.com/reference/clibrary/cstdio/sprintf.html Thanks, Regina -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Andy Anderson Sent: Friday, May 16, 2008 4:36 PM To: PostGIS Users Discussion Subject: Re: [postgis-users] Does ST_AsText truncate or round f & g are output formatting codes, f is the normal double-precision format, while g produces scientific notation (mmmE+xx) if the number is < 0.0001. The 8 and 15 represent the number of significant digits to print (for g). -- Andy On May 16, 2008, at 3:33 PM, Obe, Regina wrote: > First I can't remember what g means. I remember seeing fs and gs > somewhere before so I can only assume that f means round and g means > truncate? > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of > Paul > Ramsey > Sent: Friday, May 16, 2008 10:39 AM > To: PostGIS Users Discussion > Subject: Re: [postgis-users] Does ST_AsText truncate or round > > It all falls down into this function: > > write_double(double val){ > ensure(32); > if (lwgi) > sprintf(out_pos,"%.8g",val); > else > sprintf(out_pos,"%.15g",val); > to_end(); > } > > > > On Fri, May 16, 2008 at 3:23 AM, Paragon Corporation <[EMAIL PROTECTED]> > wrote: >> Slight clarification about what I am trying to solve. >> >> After edits I am coming back with lines that used to be intersecting > no >> longer intersecting and that still have the same AsText > representation. >> >> My hope is to reduce the precision of my geometry in the database so > the >> edits don't break the topology of my lines by doing something like > this >> >> >> Update sometable >> SET the_geom = ST_SetSRID(ST_AsText(the_geom), mysrid) >> >> >> But I fear that if AsText is doing a rounding rather than a > truncation, that >> I run the risk of breaking things that used to intersect. I am more >> concerned about under intersecting than over intersecting. >> Although I >> probably haven't thought this out enough so maybe it's a non-issue. >> >> Thanks, >> Regina >> >> >> >> -----Original Message----- >> From: [EMAIL PROTECTED] >> [mailto:[EMAIL PROTECTED] On Behalf Of > Paragon >> Corporation >> Sent: Friday, May 16, 2008 12:01 AM >> To: 'PostGIS Users Discussion' >> Subject: [postgis-users] Does ST_AsText truncate or round >> >> Hopefully this is a simple question. I know that ST_AsText returns a >> geometry that is not necessarily as prescise as what is actually > stored in >> the geometry field. I have an editor that relies on WKT > representation. >> >> Anyrate just wanted to know if the ST_AsText does a rounding of the > points >> or it does a truncation of the points. Also would be nice to know if > I >> could control the precision of this since I will need to truncate my > actual >> geometry accordingly so that both are in agreement. >> >> Thanks, >> Regina >> >> >> _______________________________________________ >> postgis-users mailing list >> postgis-users@postgis.refractions.net >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> >> _______________________________________________ >> postgis-users mailing list >> postgis-users@postgis.refractions.net >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > ----------------------------------------- > The substance of this message, including any attachments, may be > confidential, legally privileged and/or exempt from disclosure > pursuant to Massachusetts law. It is intended > solely for the addressee. If you received this in error, please > contact the sender and delete the material from any computer. > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users ----------------------------------------- The substance of this message, including any attachments, may be confidential, legally privileged and/or exempt from disclosure pursuant to Massachusetts law. It is intended solely for the addressee. If you received this in error, please contact the sender and delete the material from any computer. _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
