How is your query calculating the distance between a point and a line? Are you not just calculating the length of the line?
2009/7/10 Pavel Iacovlev <[email protected]> > Works on lines for me: > > QUERY: > select ST_length_spheroid(st_transform(the_geom, 4326), > 'SPHEROID["GRS_1980",6378137,298.257222101]') as ellps_distance, > st_distance(the_geom) as normal_distance from fondcart_layers.roads > limit 1 > > RESULT: > ellps_distance: 9214.65310341668 > normal_distance: 9214.10811677981 > > 2009/7/10 Peter Kukuča <[email protected]>: > > ST_Length_spheroid is perfectly great, but it does not take a line as an > > input :-( > > > > 2009/7/10 Pavel Iacovlev <[email protected]> > >> > >> And for geometry length use ST_length_spheroid(geometry,spheroid) > >> > >> On Fri, Jul 10, 2009 at 11:48 AM, Pavel > >> Iacovlev<[email protected]> wrote: > >> > you can take the middle of the line, > st_line_interpolate_point(the_geom, > >> > 0.5) > >> > > >> > 2009/7/10 Peter Kukuča <[email protected]>: > >> >> 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 <[email protected]> > >> >>> > >> >>> -----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 > >> >>> > > >> >>> > > >> >>> > > ---------------------------------------------------------------------- > >> >>> > > >> >>> > _______________________________________________ > >> >>> > postgis-users mailing list > >> >>> > [email protected] > >> >>> > http://postgis.refractions.net/mailman/listinfo/postgis-users > >> >>> -----BEGIN PGP SIGNATURE----- > >> >>> Version: GnuPG v1.4.7 (GNU/Linux) > >> >>> Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org > >> >>> > >> >>> iD8DBQFKVv052FH5GXCfxAsRAqS1AJ0dfphFX3wrMuo+FdXVRTgmUzHRUACfUmvH > >> >>> 146yGHfxoVmlnt9a91rpWmE= > >> >>> =G70f > >> >>> -----END PGP SIGNATURE----- > >> >>> > >> >>> _______________________________________________ > >> >>> postgis-users mailing list > >> >>> [email protected] > >> >>> http://postgis.refractions.net/mailman/listinfo/postgis-users > >> >> > >> >> > >> >> > >> >> -- > >> >> S pozdravom (regards) > >> >> Ing. Peter Kukuča > >> >> > >> >> _______________________________________________ > >> >> postgis-users mailing list > >> >> [email protected] > >> >> http://postgis.refractions.net/mailman/listinfo/postgis-users > >> >> > >> >> > >> > > >> > > >> > > >> > -- > >> > http://iap.md, The future is open > >> > > >> > >> > >> > >> -- > >> http://iap.md, The future is open > >> _______________________________________________ > >> postgis-users mailing list > >> [email protected] > >> http://postgis.refractions.net/mailman/listinfo/postgis-users > > > > > > > > -- > > S pozdravom (regards) > > Ing. Peter Kukuča > > > > _______________________________________________ > > postgis-users mailing list > > [email protected] > > http://postgis.refractions.net/mailman/listinfo/postgis-users > > > > > > > > -- > http://iap.md, The future is open > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > -- S pozdravom (regards) Ing. Peter Kukuča
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