[postgis-users] Create new lines from GPS points

[Martin Fafard]

Hi

Last step for my problem. Following the attached jpg, I need to 
highlight (create new line) the topological road (black) only when it 
intersect the green line
Any advice?
Thank you

Martin

Stephen Woodbridge a écrit :
> I think this problem has some hidden assumptions about what is the 
> rate of the incoming points, or more appropriately how close together 
> the GPS points are and with mis-alignment of GPS with respect to high 
> density road networks. If the GPS sample rate is high and the relative 
> distance is small percentage of the road network segments then the 
> problem is easier to solve because you can assume that any given point 
> is likely on the same segment as the last point or just transitioned 
> to the next segment in the network.
>
> There are still serious issue if there is a mis-alignment between the 
> GPS data and the road segments, especially in dense road network 
> areas. Here you might need to apply a stickiness to the segment you 
> are one and do additional analysis and in fact defer judgment to N-1 
> when looking at point N.
>
> Also as your sample rate spreads out and the distance between GPS 
> point increases then the last segment and the current segment might 
> not even be touching so you might need to route between the adjacent 
> GPS points. Add to this mis-alignment issues and you have a very 
> tricky problem to solve.
>
> The above issues are particularly prevalent in CDMA cell phone tower 
> assisted GPS systems that can have a lot of error in urban areas which 
> also have higher density road networks, but need to be considered with 
> any system like this.
>
> -Steve W
>
> On 1/11/2011 12:15 PM, Ralf Suhr wrote:
>> This will work. The GPS point is never on the road geometry.
>>
>> ST_Line_Substring( road,
>>
>> ST_Line_Locate_Point(road, ST_ClosestPoint(gps_start, road)),
>>
>> ST_Line_Locate_Point(road, ST_ClosestPoint(gps_end, road))
>>
>> ) AS highlight
>>
>> Gr
>>
>> Ralf
>>
>> Am Dienstag 11 Januar 2011, 18:08:29 schrieb Ralf Suhr:
>>
>>  > Hi Martin.
>>
>>  >
>>
>>  > ST_Line_Substring(road, ST_Line_Locate_Point(road, gps_start),
>>
>>  > ST_Line_Locate_Point(road, gps_end)) AS highlight
>>
>>  >
>>
>>  > Gr
>>
>>  > Ralf
>>
>>  >
>>
>>  > Am Dienstag 11 Januar 2011, 17:46:06 schrieb Martin Fafard:
>>
>>  > > Ralf
>>
>>  > >
>>
>>  > > Yes, ok for the buffer. But how to "dynamically segment" my new 
>> road
>>
>>  > > from my original segment?
>>
>>  > >
>>
>>  > > Martin
>>
>>  > >
>>
>>  > > Ralf Suhr a écrit :
>>
>>  > > > Hi Martin,
>>
>>  > > >
>>
>>  > > > you will not get a correct solution for this problem. Your road
>> network
>>
>>  > > > and the gps points differs always.
>>
>>  > > >
>>
>>  > > > A possible "solution" is building a buffer around the streets und
>> look
>>
>>  > > > für intersection with gps points and filter by direction 
>> road/points.
>>
>>  > > > Grouping gps points can give you the start and end point for the
>> road.
>>
>>  > > > If a road is only one times driven.
>>
>>  > > >
>>
>>  > > > Gr
>>
>>  > > > Ralf
>>
>>  > > >
>>
>>  > > > Am Dienstag 11 Januar 2011, 17:16:18 schrieb Martin Fafard:
>>
>>  > > >> Hi
>>
>>  > > >>
>>
>>  > > >> I have a network of roads (topological) and I receive GPS 
>> points. I
>>
>>  > > >> would like to create new lines who follow exactly the same path
>> as my
>>
>>  > > >> road from the GPS points (to "highlight" where the GPS unit was
>> on the
>>
>>  > > >> network). The problem is I need to segment the new line 
>> because the
>>
>>  > > >> GPS points can stop anywhere on my roads... Any advice to do 
>> this?
>>
>>  > > >> Thank you
>>
>>  > > >>
>>
>>  > > >> Martin F
>>
>>  > > >> _______________________________________________
>>
>>  > > >> postgis-users mailing list
>>
>>  > > >> postgis-users at postgis.refractions.net
>>
>>  > > >> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>
>>
>>
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