[postgis-users] Finding points of intersection of a linestring with another multiolygon and linestring

[Nicolas Ribot]

Hi,

Yes, you can use st_dumppoints to extract way's points and use these points
in a query with seg_wp_intersection and zone_wp_intersection to find
intersections.

Nicolas

On 1 October 2015 at 20:27, Trang Nguyen <Trang.Nguyen at inrix.com> wrote:

> I realize I didn’t clearly phrase my question:
>
>
>
> -          Is there a way to retrieve the points in the waypoints
> linestring that intersects a polygon or another linestring without having
> to write a function to traverse each point in waypoints to check whether
> the conditions st_intersects(point, seg_wp_intersection) and
> st_intersects(point, zone_wp_intersection)  are met?
>
>
>
> Any help on this would be greatly appreciated!
>
>
>
> Thanks,
>
> Trang
>
> *From:* postgis-users-bounces at lists.osgeo.org [mailto:
> postgis-users-bounces at lists.osgeo.org] *On Behalf Of *Trang Nguyen
> *Sent:* Wednesday, September 30, 2015 10:28 PM
> *To:* postgis-users at lists.osgeo.org
> *Subject:* [postgis-users] Finding points of intersection of a linestring
> with another multiolygon and linestring
>
>
>
> Hi forum,
>
>
>
> I have a LINESTRING represent the waypoints of a trip through road
> segments (LINESTRING) and zones (MULTIPOLYGON).
>
> For each segment and zone, I would like to find out the points in the
> waypoints  which intersected the targeted zone/segment geometries. First
> and last intersection point into and exiting the zone or segment  would the
> sufficient as well.
>
> I can use st_intersection to find the intersection each of waypoints to
> segment and zone geometries, but this returns a geometry that doesn’t
> necessarily contain the subset of intersecting points in the linestring.
> The query will be run on large datasets, so performance is an important
> consideration. GIST indexes exist on all the geometries joined (zone_geom,
> segment_geom and waypoints).
>
>
>
> ---------------------------
>
> Query
>
> ---------------------------
>
> select
>
> st_transform(st_intersection(segment_geom, waypoints),4326)
> seg_wp_intersection, -- need subset of points in waypoints that intersected
> with segment_geom
>
> st_transform(st_intersection(zone_geom, waypoints),4326)
>  zone_wp_intersection,  -- need subset of  points in waypoints that
> intersected with zone_geom
>
> trip_id, waypoints, zone_id, segment_id
>
> from od1.v_trip_zone_segment
>
> where
>
> startts>=TIMESTAMP '2015-01-16T12:20:29.000Z' and startts<TIMESTAMP
> '2015-01-16T17:20:30.000Z' and endts<TIMESTAMP '2015-01-16T17:20:30.000Z'
> and zone_id in
> ('kansas_303','kansas_601','kansas_603','kansas_604','kansas_10','kansas_11','kansas_9','kansas_310','kansas_311','kansas_315','kansas_301','kansas_302','kansas_307','kansas_306','kansas_305','kansas_204','kansas_201','kansas_3','kansas_2','kansas_1')
> and segment_id in
> ('5062926','5062931','5062932','4062933','5055496','5063065','5062826','5062825','5062824','5062643','5062644','5062645','5062646','5055551','5062839','5062849','5062895','5063081')
> and segment_mapversion='1501'
>
> and st_intersects(segment_geom, waypoints)
>
> and st_intersects(szone_geom, waypoints)
>
>
>
>
>
> Thanks,
>
> Trang
>
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