[postgis-users] Intersect ???

[Eduardo Bieñkowski]

Thanks for your quick response.
I'll try and I'll think about for results

2015-07-30 16:28 GMT-03:00 Rémi Cura <remi.cura at gmail.com>:

> Hey,
> answered a few weeks ago :
> http://comments.gmane.org/gmane.comp.gis.postgis/38249
> Cheers
> Rémi-C
>
> 2015-07-30 18:30 GMT+02:00 Basques, Bob (CI-StPaul) <
> bob.basques at ci.stpaul.mn.us>:
>
>> I’ve done this with a SQL statement in the past.  (it’s been a few years
>> now.)
>>
>> It was dependent on the lines actually intersecting each other
>> (diagrammatic lifework) vs physical representations.  We had to manually
>> end the line work at the intersections, and in some instances divide lines
>> that need a break at the intersections.
>>
>> You can still do the intersection extract without all this work by using
>> a gap tolerance in the search, but this may lead to more errors depending
>> on number of short street segments, etc in the dataset.
>>
>> Another way to approach this is by matching up street attributes like
>> names.  You can then derive a street intersection name index for zooming-to
>> in a map.  you’ll also likely need to use a self join of some type.
>>
>> Lastly, you can use a straight tabular method, that uses a cartiesian
>> coordinate equation and check every line segment again every other (Hint:
>> a^2 + b^2 = c^2) You don’t even need POSTGIS for this is you have the end
>> points of each line segment as coordinates.  In most cases this type of
>> search is very fast.
>>
>> I would look at the ST_INTERSECTS and possibly ST_CROSSES functions to
>> start with, but they don’t actually give up a point.
>>
>> Also, this may help get you started . . .
>>
>>
>> http://gis.stackexchange.com/questions/20835/identifying-road-intersections-using-postgis
>>
>>
>>
>> bobb
>>
>>
>> On Jul 30, 2015, at 11:06 AM, Eduardo Bieñkowski <edukoski at gmail.com>
>> wrote:
>>
>> I have one and only one layer lines (they are city streets)
>> How I can get a point layer where the lines cross? and so have a layer of
>> crosspoints
>>
>> Apologize for my English
>>
>> --
>> Eduardo
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-- 
Eduardo
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