[OpenLayers-Users] Newby: Display geoJSON Layer

Tue Jun 4 13:00:33 PDT 2013

Hi,

there is nothing wrong, but something missing. You use an unusual projection
for OpenLayers. 
OL needs to calculate the resolutions for the zoomlevels. For projection
EPSG:4326 and EPSG:900913 there are default resolutions.

Add maxExtent to your map options, then your features should displayed.

To get the extends of a geoJSON file, you can register "loadend" for the
layer and calculate the extent.

GeoJSONLayer.events.register('loadend', GeoJSONLayer, function(){
    var extent = GeoJSONLayer.getDataExtent().toBBOX().replace(/,/g,", ");
    alert("GeoJSONLayer dataExtent: " + extent);
});

little example with features from GeoJSON in projection EPSG:31466:
http://gis.ibbeck.de/ginfo/apps/OLExamples/OL212/BaseLayers/geoJson%20BaseLa
yer.asp

Arnd

  _____  

Von: openlayers-users-bounces at lists.osgeo.org
[mailto:openlayers-users-bounces at lists.osgeo.org] Im Auftrag von Helmut
Seidel M.A.
Gesendet: Dienstag, 4. Juni 2013 13:52
An: openlayers-users at lists.osgeo.org
Betreff: [OpenLayers-Users] Newby: Display geoJSON Layer

Hello everybody,

I’m absolutely new to OpenLayers – For a start I wanted to check out the
possibilities of OpenLayers and display a geoJSON-Layer which should act as
the base layer. The layer uses the projection ESPSG 31468 / DHDN /
Gauss-Krüger 4.

To say it in plain words I’m not too successfull in this, as nothing is
displayed.

I tried the following code which I copied from various sources:

<html>

                <head>

                               <script src="Lib/OpenLayers.js"></script>

                               <script type="text/javascript">

                               var map;

                               function init(){

                                               var lon = 4596651.93;

                                               var lat = 5355977.11;

                                               map = new
OpenLayers.Map('map', {

                                                               projection:
"EPSG:31468"

                                               });

                                               var kmlLayer = new
OpenLayers.Layer.Vector("GeoJSON", {

                                                               isBaseLayer:
true,

                                                               strategies:
[new OpenLayers.Strategy.Fixed()],

                                                               protocol: new
OpenLayers.Protocol.HTTP({

url: "flurstuecke.json",

format: new OpenLayers.Format.GeoJSON()

                                                               })

                                               });

                                               map.addLayers([kmlLayer]);

                                               map.addControl(new
OpenLayers.Control.MousePosition());

                                               map.setCenter(new
OpenLayers.LonLat(lon, lat), 10);

                               }

                               </script>

                </head>

                <body onload="init()">

                               <div id="map" style="width:300px;
height:300px;

                                               border: 1px solid
black;"></div>

                </body>

</html>

Can anybody tell me whats wrong with it?

By the way, how is it possible to retrive the extends of a geoJSON file?

Thank you all and regards

---

KnowHow - Helmut Seidel M.A.

Softwareentwicklung & Coaching

Gabelsbergerstraße 17 B

84034 Landshut

Telefon: 0871 9665230

Internet: www.knowhow-la.de

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