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I am trying to create a service that returns the shortest path for a given start and end destination. What I did was used shortest path query provided by pgrouting to calculate the vertex and edges that form the shortest path. Then for each of the edges I calculated their corresponding coordinates and send them as points in a gpx file. Now when I plotted the coordinates and joined them by a straight line, it gave me a path but not the curve that I needed.

I am wondering what is the best way to send that information, I mean the path information. Currently I am just sending the coordinates. So lets say for a long curve path, do I need to actually send all the intermediate points in the curve to actually plot it like a curve or is there other way.

What is the standard procedure? Thanks

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1 Answer 1

Maybe another suitable format could be GeoJSON. PostGIS can return edge geometries in GeoJSON format with ST_AsGeoJSON, so all you need to do is wrapping all edges into a GeoJSON "FeatureCollection".

You can find a simple example in the pgRouting workshop: http://workshop.pgrouting.org/chapters/php_server.html#geojson-output

You can create KML, GML, GPX or other formats in a similar way, but GeoJSON is probably the easiest one.

Update:

If you need GPX, how does your file look like? Like this should be correct:

<?xml version="1.0" encoding="UTF-8"?>
<gpx 
    xmlns="http://www.topografix.com/GPX/1/1" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd" 
    creator="" version="1.1">

    <metadata>[...]</metadata>

    <trk>
        <name>Track name</name>
<!-- Loop through your edge segments -->
        <trkseg>
            [List of points]
            <extensions></extensions>
        </trkseg>
<!-- Loop end -->
    </trk>
</gpx>

<trkseg> is described in http://www.topografix.com/GPX/1/1/#type_trksegType. You need to modify your PostgreSQL query and put the geometry in the right list format for each edge.

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no I need that to be in the gpx format –  rajan sthapit Apr 28 '12 at 2:27
    
Yeah I have tried that. For the edges that I get by running the shortest path query, I get the corresponding source and target's coordinates from there and I send the coordinates. However, I think I need to use the geometry feature as well, because just joining the points by straight line doesn't work. So how can I accomplish this.Could you please elaborate more? What do you mean by put the geometry in the right list format? –  rajan sthapit Apr 28 '12 at 11:27
    
The format you have given is the same as I have used. But the issue is the edges given by the query sometimes, they have overlaps and when I display it, it doesn't look good. I have just sent the coordinates now for each edge. But it's not working in my case. So it will be like <trkseg>all points all edges in the order returned by the query </trkseg> –  rajan sthapit Apr 28 '12 at 11:44
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