[postgis-users] Postgis - Line to Point distance

[Pavel Iacovlev]

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>
>>
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>> 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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>
>



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