Re: [postgis-users] LinearReferencing: measure vertex of linestring?
http://trac.osgeo.org/postgis/ticket/1747 ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] LinearReferencing: measure vertex of linestring?
On Wed, Mar 28, 2012 at 06:22:28PM +0200, Andrés Maneiro wrote: LINESTRINGM(1 0 1,2 0 2,4 0 4) What I'm wondering is if somehow I could calibrate the vertex of the linestring, having as a result, for example, this route: LINESTRINGM(1 0 1,2 0 *1.7*,4 0 4) See ST_SetPoint --strk; ,--o-. | __/ |Delivering high quality PostGIS 2.0 ! | / 2.0 |http://strk.keybit.net - http://vizzuality.com `-o--' ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] LinearReferencing: measure vertex of linestring?
On 28/03/12 18:26, Sandro Santilli wrote: On Wed, Mar 28, 2012 at 06:22:28PM +0200, Andrés Maneiro wrote: LINESTRINGM(1 0 1,2 0 2,4 0 4) Oh, I get it. And there is a native way in postgis to calibrate the line from a given set of measured points instead of using the ends? -- If I understand it correctly I could: 1) mylinestringm = ST_AddMeasure(mylinestring, measure_start, measure_end); 2) Add the given set of points to mylinestringm with ST_AddPoint 3) Using ST_SetPoint to move the original vertexes. Is that correct? I'm very interested to know if there is a more direct and proper way to create a route from a set of points. best, Andrés ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] LinearReferencing: measure vertex of linestring?
On 3/28/2012 1:26 PM, Andrés Maneiro wrote: On 28/03/12 18:26, Sandro Santilli wrote: On Wed, Mar 28, 2012 at 06:22:28PM +0200, Andrés Maneiro wrote: LINESTRINGM(1 0 1,2 0 2,4 0 4) Oh, I get it. And there is a native way in postgis to calibrate the line from a given set of measured points instead of using the ends? -- If I understand it correctly I could: 1) mylinestringm = ST_AddMeasure(mylinestring, measure_start, measure_end); 2) Add the given set of points to mylinestringm with ST_AddPoint 3) Using ST_SetPoint to move the original vertexes. Is that correct? I'm very interested to know if there is a more direct and proper way to create a route from a set of points. ST_MakeLine [1] can be used to aggregate a sequence of points into a line. [1] http://www.postgis.org/documentation/manual-1.5/ST_MakeLine.html ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] LinearReferencing: measure vertex of linestring?
I guess the best way to do this is to combine the actual line and a virtual line, probably a view, with measured points. This involves a bit of thinking but it might be possible. George On Wed, Mar 28, 2012 at 3:03 PM, Stephen Woodbridge wood...@swoodbridge.com wrote: On 3/28/2012 1:26 PM, Andrés Maneiro wrote: On 28/03/12 18:26, Sandro Santilli wrote: On Wed, Mar 28, 2012 at 06:22:28PM +0200, Andrés Maneiro wrote: LINESTRINGM(1 0 1,2 0 2,4 0 4) Oh, I get it. And there is a native way in postgis to calibrate the line from a given set of measured points instead of using the ends? -- If I understand it correctly I could: 1) mylinestringm = ST_AddMeasure(mylinestring, measure_start, measure_end); 2) Add the given set of points to mylinestringm with ST_AddPoint 3) Using ST_SetPoint to move the original vertexes. Is that correct? I'm very interested to know if there is a more direct and proper way to create a route from a set of points. ST_MakeLine [1] can be used to aggregate a sequence of points into a line. [1] http://www.postgis.org/**documentation/manual-1.5/ST_**MakeLine.htmlhttp://www.postgis.org/documentation/manual-1.5/ST_MakeLine.html __**_ postgis-users mailing list postgis-users@postgis.**refractions.netpostgis-users@postgis.refractions.net http://postgis.refractions.**net/mailman/listinfo/postgis-**usershttp://postgis.refractions.net/mailman/listinfo/postgis-users -- George R. C. Silva Desenvolvimento em GIS http://geoprocessamento.net http://blog.geoprocessamento.net ___ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
Re: [postgis-users] LinearReferencing: measure vertex of linestring?
Create a ticket describing the calibration, that's useful info and
would be a good utility for LRS users for a future version.
P.
2012/3/28 Andrés Maneiro amane...@icarto.es:
Hello people,
I'm reviewing what postgis is able to do in terms of Linear Referencing. As
fas as I could see, to calibrate a linestring there is only the method
ST_AddMeasure:
http://www.postgis.org/docs/ST_AddMeasure.html
So, as stated in the example, the operation will create a route like:
SELECT ST_AsEWKT(ST_AddMeasure(
ST_GeomFromEWKT('LINESTRING(1 0, 2 0, 4 0)'),1,4)) As ewelev;
ewelev
LINESTRINGM(1 0 1,2 0 2,4 0 4)
What I'm wondering is if somehow I could calibrate the vertex of the
linestring, having as a result, for example, this route:
LINESTRINGM(1 0 1,2 0 *1.7*,4 0 4)
The project I'm working on is related to road management, and it's very
common that the ratio between a route's length and its measures is not
constant. So, my doubt goes: is it somehow possible to create a route in
postgis where the measure and the distance are not directly related?
(For those who know how ArcGIS dynamic segmentation works, what I'd like
to achive is something similar to calibrate a route using points [1]).
Let me know if I explain myself properly.
best,
Andrés
[1]
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/About_calibrating_route_measures_using_points/0039000t00/
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