[postgis-users] PostGIS to calculate time spent within polygon

[Masanao Yajima]

Hi Everyone

Thank you!!
That was very helpful, I might be able to pull it off.
I'm still struggling to implement it but will report back when I get a
result.
If anyone else has more suggestions I'm all ears.

Masanao Y

On Wed, Oct 7, 2009 at 12:42 AM, Suhr, Ralf <Ralf.Suhr at itc-halle.de> wrote:

> I think the best solution a join from the inersect line and the gps-points
> group by min/max time. Because the intersect line havn't M-values and the
> first and the last point from line haven't corrospondending gps-points.
>
> Gr Ralf
>
> -----Ursprüngliche Nachricht-----
> Von: postgis-users-bounces at postgis.refractions.net [mailto:
> postgis-users-bounces at postgis.refractions.net] Im Auftrag von Simon
> Greener
> Gesendet: Mittwoch, 7. Oktober 2009 07:38
> An: PostGIS Users Discussion
> Betreff: Re: [postgis-users] PostGIS to calculate time spent within polygon
>
> I haven't used the Linear referencing funcitons of PostGIS but perhaps this
> might help.
>
> First find the intersection points of the measured line and the polygon
> using ST_Intersection. Don't worry about loosing the M in the returned data
> - what you want is the point at which the line enters (ST_StartPoint) and
> leaves (ST_EndPoint).
>
> Then use these points and the appropriate Linear referencing functions (
> http://postgis.refractions.net/documentation/manual-1.4/ch07.html#Linear_Referencing)
> to compute the time measure values where the line enters the polygon and
> when it leaves.
>
> regards
> Simon
>
>
> http://postgis.refractions.net/documentation/manual-1.4/ST_Line_Locate_Point.html
> On Wed, 07 Oct 2009 14:19:37 +1100, George Silva <georger.silva at gmail.com>
> wrote:
>
> > You can select the interval between minimun and maximum timestamp outside
> > each polygon. Interpolate to get a value "when entering" the polygon
> > (intersection between line and polygon) and when leaving.
> >
> > Then you can subtract both values to get an estimate of time.
> >
> > You probably can write a simple function for this.
> >
> > George
> >
> > On Tue, Oct 6, 2009 at 11:18 PM, Masanao Yajima <yajiyajijp at yahoo.co.jp
> >wrote:
> >
> >> Thank you for your response.
> >>
> >> However, would it be possible to elaborate on the 2nd part?
> >> If my reading of the manual is correct,
> >> I believe st_intersection is not implemented to handle the 4th
> dimension.
> >>
> >> Masanao Yajima
> >>
> >> On Tue, Oct 6, 2009 at 6:47 AM, Suhr, Ralf <Ralf.Suhr at itc-halle.de>
> wrote:
> >>
> >>>  Hello Masanao Yajima,
> >>>
> >>>
> >>>
> >>> for db-design you can go with ogr2ogr (GPX -> PostGIS). Ogr2ogr creates
> >>> point and line geometrys from gpx files. In case of linestring you have
> to
> >>> add the 4. Dimension from the point table.
> >>>
> >>> A optimal query would be the intersection from gps-linestrings and your
> >>> polygon area. The result can be many sublinestrings with start and end
> time.
> >>>
> >>>
> >>>
> >>> Gr Ralf
> >>>
> >>>
> >>>
> >>> *Von:* postgis-users-bounces at postgis.refractions.net [mailto:
> >>> postgis-users-bounces at postgis.refractions.net] *Im Auftrag von
> *Masanao
> >>> Yajima
> >>> *Gesendet:* Montag, 5. Oktober 2009 23:03
> >>> *An:* postgis-users at postgis.refractions.net
> >>> *Betreff:* [postgis-users] PostGIS to calculate time spent within
> polygon
> >>>
> >>>
> >>>
> >>> Dear PostGIS users
> >>>
> >>> I am new to PostGIS and I would like expert opinion on how to deal with
> my
> >>> situation.
> >>>
> >>> I have 2D GPS data and time associated with each points and they
> >>> represents line of a trip.
> >>> I also have few geographic polygon data representing some area on a
> map.
> >>>
> >>> what I want to get out is length of time that is spent within polygon
> area
> >>> for a trip.
> >>>
> >>> What is the optimal way to design a database and what kind of query
> would
> >>> you use to get such a number.
> >>>
> >>> One constraint is the time interval for GPS is not accurate so sampling
> >>> rate vary alot with in a trip.
> >>>
> >>> I thought of using time as 4th dimension but I believe st_intersection
> is
> >>> not implemented on the 4th dimension..
> >>>
> >>> I could do this by bruit force but I am looking for something fast.
> >>>
> >>> I appreciate your help.
> >>>
> >>> --
> >>> Masanao Yajima
> >>>
> >>> _______________________________________________
> >>> postgis-users mailing list
> >>> postgis-users at postgis.refractions.net
> >>> http://postgis.refractions.net/mailman/listinfo/postgis-users
> >>>
> >>>
> >>
> >>
> >> --
> >> Masanao Yajima
> >>
> >> _______________________________________________
> >> postgis-users mailing list
> >> postgis-users at postgis.refractions.net
> >> http://postgis.refractions.net/mailman/listinfo/postgis-users
> >>
> >>
> >
> >
>
>
> --
> SpatialDB Advice and Design, Solutions Architecture and Programming,
> Oracle Database 10g Administrator Certified Associate; Oracle Database 10g
> SQL Certified Professional
> Oracle Spatial, SQL Server, PostGIS, MySQL, ArcSDE, Manifold GIS, FME,
> Radius Topology and Studio Specialist.
> 39 Cliff View Drive, Allens Rivulet, 7150, Tasmania, Australia.
> Website: www.spatialdbadvisor.com
>   Email: simon at spatialdbadvisor.com
>   Voice: +61 362 396397
> Mobile: +61 418 396391
> Skype: sggreener
> Longitude: 147.20515 (147° 12' 18" E)
> Latitude: -43.01530 (43° 00' 55" S)
> GeoHash: r22em9r98wg
> NAC:W80CK 7SWP3
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
>



-- 
Masanao Yajima
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20091007/2923bcf5/attachment.html>