[postgis-users] Postgis - Line to Point distance

[Peter Kukuča]

ST_Length_spheroid is perfectly great, but it does not take a line as an
input :-(

2009/7/10 Pavel Iacovlev <iacovlev.pavel at gmail.com>

> And for geometry length use ST_length_spheroid(geometry,spheroid)
>
> On Fri, Jul 10, 2009 at 11:48 AM, Pavel
> Iacovlev<iacovlev.pavel at gmail.com> wrote:
> > you can take the middle of the line, st_line_interpolate_point(the_geom,
> 0.5)
> >
> > 2009/7/10 Peter Kukuča <pjr.kukuca at gmail.com>:
> >> Hi Pedro,
> >>
> >> thank you for your reply.
> >>
> >> I cannot use pointn, the line can be up to several hundred kilometers
> long
> >> and consits of up to 800 points, so this would be too rough.
> >>
> >> Regardinf the decond suggestion, that is exactly what I am doing now,
> but I
> >> don't know, which projection (srid) to transform the wgs84 data into. It
> >> should work on all of the earth's surface, at least in all of europe for
> a
> >> start. And from what I found, the projections are usually tied to a
> small
> >> territory. I was thinking about mercator projection, but there is a
> zillion
> >> of them in postgis. And I found a post, that the one with srid 900913 is
> >> working great, but I don't have that one in my postgis.
> >>
> >> 2009/7/10 Pedro Doria Meunier <pdoria at netmadeira.com>
> >>>
> >>> -----BEGIN PGP SIGNED MESSAGE-----
> >>> Hash: SHA1
> >>>
> >>> Hi Peter
> >>>
> >>> You could use the pointn(geometry, n) for the first point of the
> >>> linestring as a first approach.
> >>> As far as meters are concerned here's a little example of transforming
> >>> the geometry to the desired projected system:
> >>>
> >>> select distance(transform(u.coordinates,srid),
> >>> transform(p.geometry,srid)) AS thedistance
> >>>
> >>> HTH,
> >>>
> >>> Pedro Doria Meunier
> >>> GSM: +351 96 17 20 188
> >>> Skype: pdoriam
> >>>
> >>>
> >>>
> >>>
> >>> Peter Kukuča wrote:
> >>> > Dear sir,
> >>> >
> >>> > I am not sure if I am writing to the correct email address. I have
> >>> > found a post on the postgis-users formu from *Rich Gibson *and this
> >>> > address was next to it.
> >>> >
> >>> > I am using postgis for a while now and it is great. It solved a lot
> >>> > of problems for me.
> >>> >
> >>> > However, I am now facing a problem I cannot solve. I searched for
> >>> > almost two days now, but I still cannot find an answer. Here is my
> >>> > problem:
> >>> >
> >>> > I have a database of linestrings in wgs84 projection and points in
> >>> > wgs84 projection. I would like to determine the distance between a
> >>> > line and a point. The ST_distance function does this very well, but
> >>> > it does not take the wgs84 projection into account and also, the
> >>> > result is in degrees. On the other hand, the ST_Distance_Spheroid
> >>> > does take the wgs84 into accound and does give the result in meters,
> >>> > but it does not accept a linestring as an input parameter.
> >>> >
> >>> > Is there any way i can the distance between a line and a point in
> >>> > meters from the wgs84 projected input? I do not need grat accuracy.
> >>> > +-5 meters is still good enough. Thank you for your tips.
> >>> >
> >>> > --
> >>> > S pozdravom (regards)
> >>> > Ing. Peter Kukuča
> >>> >
> >>> >
> ----------------------------------------------------------------------
> >>> >
> >>> > _______________________________________________
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> >>
> >>
> >>
> >> --
> >> S pozdravom (regards)
> >> Ing. Peter Kukuča
> >>
> >> _______________________________________________
> >> postgis-users mailing list
> >> postgis-users at postgis.refractions.net
> >> http://postgis.refractions.net/mailman/listinfo/postgis-users
> >>
> >>
> >
> >
> >
> > --
> > http://iap.md, The future is open
> >
>
>
>
> --
> http://iap.md, The future is open
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>



-- 
S pozdravom (regards)
Ing. Peter Kukuča
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