[postgis-users] Postgis - Line to Point distance

Pavel Iacovlev iacovlev.pavel at gmail.com
Fri Jul 10 01:52:31 PDT 2009


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
>>
>> _______________________________________________
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>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>
>>
>
>
>
> --
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