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
