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Adding a single boundary layer with default styling

How do we add a single boundary layer with default styling? We are going to build on displaying a marker tutorial. In this tutorial we created an HTML document with all the appropriate tags and included a DIV tag which gave instructions on how to display the map. The heavy lifting is all done within the javascript section (between the script…/script tags). The instructions in this document will deal with this core of the code. Essentially we will be replacing the content of displaying a marker tutorial script tags, with the following:


<script type="text/javascript">
var osMap, boundaryLayer;
function init()
{
osMap = new OpenSpace.Map('map');
var options = {strategies: [new OpenSpace.Strategy.BBOX()],
area_code: ["CTY" ]
};
boundaryLayer = new OpenSpace.Layer.Boundary("Boundaries", options);
osMap.addLayer(boundaryLayer);
osMap.setCenter(new OpenSpace.MapPoint(400000, 200000), 2);
}
</script>

Let's break this up

We start a script tag to contain our code:


<script type="text/javascript">

Then we create a map object variable, osMap and a boundaryLayer object variable, boundaryLayer:


var osMap, boundaryLayer;

Now we define our init function:


function init()
{

Create a new OS OpenSpace map object and pass it our 'map' element id. This is the HTML div that will hold the map.


osMap = new OpenSpace.Map('map');

Then we create an options variable that contains strategies that will be used to refine the boundaries that are returned. The bounding box strategy(OpenSpace.Strategy.BBOX()) is compulsory. The area_code is one such strategy of which there are others (see documentation). In this case we just wish to return only county boundaries (area_code = "CTY"):


var options = {strategies: [new OpenSpace.Strategy.BBOX()],
area_code: ["CTY" ]
};

Then we populate our boundaryLayer object using the syntax required to return boundaries and with the options that we have just defined:


boundaryLayer = new OpenSpace.Layer.Boundary("Boundaries", options);

Then we add the boundary layer to the map:


osMap.addLayer(boundaryLayer);

However, we then need to move the map around so that the boundaries are actually returned. This can be the same as the current location:


osMap.setCenter(new OpenSpace.MapPoint(400000, 200000), 2);
}

Finally close the script.


</script>

The full code can be found below:


<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Open Space Tutorial 6</title>
<script type="text/javascript"
src="http://openspace.ordnancesurvey.co.uk/osmapapi/openspace.js?key=insert_your_api_key_here"></script>
<script type="text/javascript">
var osMap, boundaryLayer;
function init()
{
osMap = new OpenSpace.Map('map');
var options = {strategies: [new OpenSpace.Strategy.BBOX()],
area_code: ["CTY" ]
};
boundaryLayer = new OpenSpace.Layer.Boundary("Boundaries", options);
osMap.addLayer(boundaryLayer);
osMap.setCenter(new OpenSpace.MapPoint(400000, 200000), 2);
}
</script>
</head>
<body onload="init()">
<H1>Add a boundary</H1>
<div id="map" style="width: 500px; height: 300px; border: 1px solid
black;"></div>
</body>
</html>
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