AW: AW: [postgis-users] Re:PHP access to PostGIS

[Düster Horst]

Hi Martin

> By line snap do you mean snap to an arbitrary point on a
> line string belonging to a polyline or polygon? 

That's what I meant. The point should snap to the closest point on a line
belonging to a polyline or polygon. Take a look at the attached image.

With best regards

Horst

---------------------------------
 
Dr. Horst Düster 
GIS-Koordinator /Amtschef Stv.

Kanton Solothurn 
Amt für Geoinformation
Abteilung SO!GIS Koordination
Werkhofstr. 65
CH-4509 Solothurn 

Tel.: ++41 (0)32 627 25 32 
Fax: ++41 (0)32 627 22 14

horst.duester at bd.so.ch 
www.sogis.so.ch



-----Ursprüngliche Nachricht-----
Von: Stephen Woodbridge [mailto:woodbri at swoodbridge.com]
Gesendet am: Sonntag, 20. März 2005 15:22
An: PostGIS Users Discussion
Betreff: Re: AW: [postgis-users] Re:PHP access to PostGIS

Martin,

I had a different read on this request. I think the idea in line snap 
would be to identify the two portions of the line that are roughly 
coincident or adjacent to the another line ("line" being a line, 
polyline, polygon edge, etc.) and cause the two line portions to "snap" 
to one another. This would require identifying to two coincident 
sections, then modifying them so they have the same vertex points along 
the "snapped" edge.

Of course, this may not be what to original poster had in mind :)

-Steve

Martin Høgh wrote:
> Hi Horst, By line snap do you mean snap to an arbitrary point on a
> line string belonging to a polyline or polygon? And the possibility
> of adding a new vertex where the snap occurred?
> 
> I've though of this and it's a very good idea. I'll think about how
> this could be accomplished.
> 
> /Martin
> 
> ********
> 
> Martin
> 
> I took a look at your snap function. I works nice with single vertex
> snap, but a linesnap is not available. That means, that two lines
> with different number of vertexpoints doesn't snap correct. I'm sure
> that you are aware of this circumstance. Are your interested to
> enhance your snap function with this feature? Further I think, that
> an add vertex function with linesnapping could be a very helpful
> thing. With these mensioned enhancements and your geometry class it
> is possible to build a wide featured web editing tool.
> 
> What do you think about my ideas?
> 
> Horst
> 
> 
> 
> 
> -----Ursprüngliche Nachricht----- Von: "Martin Høgh" [mailto:mh at
> svaj.dk] Gesendet am: Freitag, 11. März 2005 17:30 An: postgis-users
> at postgis.refractions.net Betreff: [postgis-users] Re:PHP access to
> PostGIS
> 
> Hi, Yes of couse.
> 
> If you want to do snap the geometry to another geometry so they
> thouch, you can use this function
> 
> $g->snapShape($shapeId,$snapTolerance,$snapLayerStr);
> 
> A geometry feature comprises one or more shapes (more if
> multigeometry). The shapeId is the id of the shape you want to snap,
> tolerance is the snap tolerance and snapLayerStr is a string with
> coords "x1 y1,x2, y2...." which will be evaluated. If a coord in
> shape with shapId lies within the tolerance from the coords of
> snapLayerStr, it'll be snapped to this.
> 
> e.g.
> 
> $g->snapShape(0,5,"3 3, 4 4, 8 8");
> 
> If you want to snap two geometries
> 
> $g1->snapShape(0,5,$g2->getVertices());
> 
> shape with id 0 of $g1 will be altered if it has coords that lies
> within a distance of 5 from the coords of $g2.
> 
> there is also the method:
> 
> $g0->snapAllShapes($snapTolerance,$snapLayerStr);
> 
> This will loop through all shapes of $g and snap them.
> 
> Soon I will start on writing some documentation.
> 
> /martin
> 
> ****
> 
> 
> Martin
> 
> Your geometry class sounds very interesting. Could you made some
> further explanations particulary the snap functions. I couldn't
> understand what you do mean with the snapLayerStr.
> 
> 
> With best regards
> 
> Horst _______________________________________________ postgis-users
> mailing list postgis-users at postgis.refractions.net 
> http://postgis.refractions.net/mailman/listinfo/postgis-users
> 

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