[OpenLayers-Users] Showing points from a database

Sun Sep 21 10:19:32 PDT 2014

Hi,

your map is in projection EPSG:900913 (OSM). 
Are your data also in this projection or perhaps in EPSG:4326 (lonlat)?

If so, it could be that your data are shown (at x=0,y=0), but you only can't
see them.

Regards,
Arnd

  _____  

Von: openlayers-users-bounces at lists.osgeo.org
[mailto:openlayers-users-bounces at lists.osgeo.org] Im Auftrag von Niccolò Dal
Santo
Gesendet: Freitag, 19. September 2014 23:11
An: Mark Prins
Cc: openlayers-users
Betreff: Re: [OpenLayers-Users] Showing points from a database

Thank you very much for your answer. I have therefore started to investigate
the possiblity to use the GeoJSON format, and now I am trying to train with
this format with this example but it doesn't work 

    <script type="text/javascript">

    var map = new OpenLayers.Map("my_map");

    var layer = new OpenLayers.Layer.OSM("OpenStreetMap");
    map.addLayer(layer);

    map.addControl(new OpenLayers.Control.LayerSwitcher());
    map.setCenter(new OpenLayers.LonLat(0,0), 2);

    var citiesLayer = new OpenLayers.Layer.Vector("World Cities (GeoJSON)", 

        {   protocol: new OpenLayers.Protocol.HTTP({
            url: "http://localhost/openlayers/world_cities.json",
            format: new OpenLayers.Format.GeoJSON()
        }),
        strategies: [
            new OpenLayers.Strategy.Fixed(), 
            new OpenLayers.Strategy.Cluster({distance: 15})
        ]
    });
    map.addLayer(citiesLayer);
</script>

In order to make the protocol work I have installed nginx on my laptop and
the url correctly points to the file world_cities.json in my browser. Anyway
this example doesn't work, any idea why?

Thanks! 
Niccolò

2014-09-19 15:54 GMT+02:00 Mark Prins <mc.prins at gmail.com>:

using plain text or (geo) json is much less error prone than using
GML, and probably gives better performance

2014-09-19 15:45 GMT+02:00 Niccolò Dal Santo <ncl.dalsanto at gmail.com>:
> Hi there,
>
> I am new of Openlayers and I need to show some points that come from a
> database on a map centred in Turin (Italy), with some information related
to
> this point (for instance an image). Searching on line I have found that
> Openlayers supports many formats of data like GML, KML, GeoJSON and many
> others. Could you suggest a format useful fror my problem and maybe some
> examples of how to use it?
>
> I have tried with this code generating a map of europe, but it doesn't
work
>
> <html>
> <head>
>   <title>Prova GML</title>
>     <script src="http://openlayers.org/api/OpenLayers.js"></script>
> </head>
>     <body>
>     <div id="ch3_gml" style="width: 100%; height: 100%;"></div>
>
>     <script type="text/javascript">
>
>         // Create the map using the specified DOM element
>         var map = new OpenLayers.Map("ch3_gml");
>
>         var layer = new OpenLayers.Layer.OSM("OpenStreetMap");
>         map.addLayer(layer);
>
>         map.addControl(new OpenLayers.Control.LayerSwitcher());
>         map.setCenter(new OpenLayers.LonLat(0,0), 2);
>
>         map.addLayer(new OpenLayers.Layer.Vector("Europe (GML)", {
>             protocol: new OpenLayers.Protocol.HTTP({
>                 url: "./europe.gml",
>                 format: new OpenLayers.Format.GML()
>             }),
>             strategies: [new OpenLayers.Strategy.Fixed()]
>         }));
>     </script>
> </body>
> </html>
>
> where europe.gml is a gml file in the same folder of this script, but
> nothing happens.
>
> Thank you very much for your help!
>
> Regards
>
> Niccolò
>
> --
> Niccolò Dal Santo
> +39 342 15 70 842 <tel:%2B39%20342%2015%2070%20842> 
> ncl.dalsanto at gmail.com
>

> _______________________________________________
> Users mailing list
> Users at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/openlayers-users

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Niccolò Dal Santo 
+39 342 15 70 842
ncl.dalsanto at gmail.com

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