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 >
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