[postgis-devel] error in ST_ModEdgeSplit

[Rémi Cura]

OUps, forgot to mention.
Split function taht works for line, point argument, and take account
precision :
https://github.com/Remi-C/PPPP_utilities/blob/aa802f136cc3768d987b77cb3a4d04e9f6a74344/postgis/rc_Split_Line_By_Points.sql
Cheers,
Rémi-C

2015-02-11 13:45 GMT+01:00 Rémi Cura <remi.cura at gmail.com>:

> Solved by introducing precision (topology precision),
> and another split function (st_split(line, point) is not reliable).
>
> The edge is not moved in this case, it is the node that is moved,
> thus the topology is safe
>
> Cheers,
> Rémi-C
>
> 2015-02-11 12:28 GMT+01:00 Sandro Santilli <strk at keybit.net>:
>
>> On Wed, Feb 11, 2015 at 12:02:13PM +0100, Rémi Cura wrote:
>> > Hey,
>> >
>> > I get an error with ST_ModEdgeSplit that looks like aa precision related
>> > issue.
>> >
>> > When trying to split an edge with a point (the point is from
>> > ST_ClosestPoint, so _very_ close to the edge),
>> > st_modeedgesplit complains that the point is not on the edge.
>>
>> This is a known issue. I've mixed feeling about what the function
>> should do because "ST_" prefixed functions supposedly come from
>> the standard that makes no mention of "precision".
>>
>> The toTopoGeom function handles that by first snapping the edge against
>> the point retrived by "ClosestPoint". Note that such snapping might
>> move the edge in a way that it could end up colliding against another
>> edge. This may happen if the intersection node you found is close to
>> another existing node and between two indicent edges almost parallel.
>> There's no primitive function handling such case, which would involve
>> updating partially merging the two edges into one.
>>
>> --strk;
>>
>>   ()   Free GIS & Flash consultant/developer
>>   /\   http://strk.keybit.net/services.html
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>>
>
>
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