[postgis-users] st_split

[franco base]

Hi.
Yes the cause can be that every function has his own "tolerance"

SELECT line,geom_line,point,geom_point,
ST_ClosestPoint(geom_line,geom_point), ----- return geometry=geom_point
ST_distance (geom_line,geom_point), ---- return 0
ST_contains(geom_line,geom_point) ---- return false

"line";"geom_line";"point";"geom_point";"st_closestpoint";"st_distance";"st_contains"
7646;"0102000020BB0B000006000000A4703D0A471F37412D211F04AF335341FAEDEBE0491F3741325530C2AE335341BD5296014F1F37418FC2F578AE3353414694F606521F3741D2DEE07BAE3353412D211F74541F37418FC2F578AE33534123B9FC675020374112143FF6BC335341";11764;"0101000020BB0B00005713362F611F37410D996234AF335341";"0101000020BB0B00005713362F611F37410D996234AF335341";0;f
7646;"0102000020BB0B000006000000A4703D0A471F37412D211F04AF335341FAEDEBE0491F3741325530C2AE335341BD5296014F1F37418FC2F578AE3353414694F606521F3741D2DEE07BAE3353412D211F74541F37418FC2F578AE33534123B9FC675020374112143FF6BC335341";11769;"0101000020BB0B00005EF0DD584620374139BF2762BC335341";"0101000020BB0B00005EF0DD584620374139BF2762BC335341";0;f
7646;"0102000020BB0B000006000000A4703D0A471F37412D211F04AF335341FAEDEBE0491F3741325530C2AE335341BD5296014F1F37418FC2F578AE3353414694F606521F3741D2DEE07BAE3353412D211F74541F37418FC2F578AE33534123B9FC675020374112143FF6BC335341";11762;"0101000020BB0B0000A5CBC785841F374156A2A33CB1335341";"0101000020BB0B0000A5CBC785841F374156A2A33CB1335341";0;f

Remi I don't undesrtand very well your tip to translate date and use
St_SnapToGrid

I cannot snap (using St_Snap) line to point because I'm working on a road
network and I cannot move the line versus point.


Thanks
fb


2013/10/28 Rémi Cura <remi.cura at gmail.com>

> I had the same problem,
> all function don't react the same way when hitting precision limit.
>
> You may want to translate your data to reduce digits, and/or use
> ST_SnapToGrid on everything before using ST_ClosestPoint.
>
> Cheers,
> Rémi-C
>
>
> 2013/10/28 Nicolas Ribot <nicolas.ribot at gmail.com>
>
>> Hmm this is strange:
>>
>> Finding the closest point (st_closestPoint) or using
>> st_lineLocatePoint to project point onto the line does not work either
>> on the provided dataset.
>> Though the st_distance(line, point) returns 0.
>>
>> Nicolas
>>
>>
>>
>> On 28 October 2013 18:42, Rémi Cura <remi.cura at gmail.com> wrote:
>> > You may want to split not with point but with the projected point one
>> line
>> > (use http://postgis.refractions.net/docs/ST_ClosestPoint.html)
>> > If it is not enough, you may want to translate all your geometries to
>> reduce
>> > the number of digits in coordinates.
>> > Another possibility is to use ST_Snap to snap line to point (won't work
>> the
>> > other way)
>> >
>> > Cheers,
>> > Rémi-C
>> >
>> >
>> > 2013/10/28 Nicolas Ribot <nicolas.ribot at gmail.com>
>> >>
>> >> Hi,
>> >>
>> >> The points are not on the line, probably due to rounding errors.
>> >>
>> >> st_contains(line, point) returns false.
>> >>
>> >> Nicolas
>> >>
>> >> On 28 October 2013 18:07, franco base <frenk.calza at gmail.com> wrote:
>> >> > Hi.
>> >> > I have a set of linestring and point on linestring.
>> >> > I want cut the linestring on the point.
>> >> > I can have n points for one linestring,
>> >> > so I use ST_Split
>> >> > (insted of ST_Line_Interpolate_Point and ST_Line_Substring)
>> >> > but it doesn't work.
>> >> >
>> >> > line;geom_line;point;geom_point
>> >> >
>> >> >
>> 7646;"0102000020BB0B000006000000A4703D0A471F37412D211F04AF335341FAEDEBE0491F3741325530C2AE335341BD5296014F1F37418FC2F578AE3353414694F606521F3741D2DEE07BAE3353412D211F74541F37418FC2F578AE33534123B9FC675020374112143FF6BC335341";11764;"0101000020BB0B00005713362F611F37410D996234AF335341"
>> >> >
>> >> >
>> 7646;"0102000020BB0B000006000000A4703D0A471F37412D211F04AF335341FAEDEBE0491F3741325530C2AE335341BD5296014F1F37418FC2F578AE3353414694F606521F3741D2DEE07BAE3353412D211F74541F37418FC2F578AE33534123B9FC675020374112143FF6BC335341";11769;"0101000020BB0B00005EF0DD584620374139BF2762BC335341"
>> >> >
>> >> >
>> 7646;"0102000020BB0B000006000000A4703D0A471F37412D211F04AF335341FAEDEBE0491F3741325530C2AE335341BD5296014F1F37418FC2F578AE3353414694F606521F3741D2DEE07BAE3353412D211F74541F37418FC2F578AE33534123B9FC675020374112143FF6BC335341";11762;"0101000020BB0B0000A5CBC785841F374156A2A33CB1335341"
>> >> >
>> >> > ST_GeometryType(St_Split(geom_line, geom_point))
>> >> > give "ST_GeometryCollection"
>> >> >
>> >> > but
>> >> >
>> >> > (ST_Dump(ST_Split(geom_line, geom_point))).geom
>> >> >
>> >> > return only 3 linestring (one for record) and the geometry is egual
>> to
>> >> > geom_line
>> >> >
>> >> >
>> >> > thanks.
>> >> >
>> >> > fb
>> >> >
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