Norwegian Polar Institute Maps API - Javascript

Getting Started

Overview

NPI provides topographic maps of Svalbard and Jan Mayen served at geodata.npolar.no/arcgis/rest/services. These maps can be consumed through various client applications such as ArcGIS API for JavaScript, Google Maps API, OpenLayers etc. to easily create a mapping application.

This documentation shows how to quickly setup and develop an interactive web map application for the Svalbard region using ArcGIS API for Javascript, including adding place name search, working with map overlays and popups and dealing with map services. The ArcGIS API for JavaScript is a lightweight way to embed maps and tasks in web applications similar to Google Maps API with more advanced functionalities, such as geoprocessing, network analysis and data editing.

Audience

This documentation is designed with the assumption that you are familiar with basic JavaScript programming and mapping concepts (such as Google Maps). It's also desirable if you make yourself familiar with Esri's ArcGIS API for Javascript to take full advantage of the mapping API.

Setting The Map

The easiest way to setup a map of Svalbard using ArcGIS API for JavaScript is to see a simple example. The following html page displays a map of Svalbard centered around Longyearbyen:

<!DOCTYPE html>
<html>
  <head>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
    <link rel="stylesheet" href="http://geodata.npolar.no/arcgis_js_api/library/3.8/3.8/js/esri/css/esri.css"/>
    <style type="text/css">
      html { height: 100% }
      body { height: 100%; margin: 0; padding: 0 }
      #map { height: 100% }
    </style>
    <script src="http://geodata.npolar.no/arcgis_js_api/library/3.8/3.8/init.js"></script>
    <script type="text/javascript">
      dojo.require("esri.map");
      function initialize() {
    var initialExtent = new esri.geometry.Extent({
        "xmin": 477423.89,
        "ymin":8663685.98,
        "xmax":553624.05,
        "ymax":8714486.09,
        "spatialReference":{"wkid":25833}
        });
    // create map instance and add a basemap
    map = new esri.Map("map", {extent: initialExtent, logo : false});
    basemapURL = "http://geodata.npolar.no/arcgis/rest/services/Basisdata/NP_Basiskart_Svalbard_WMTS_25833/MapServer"
    map.addLayer(new esri.layers.ArcGISTiledMapServiceLayer(basemapURL));
    }

    dojo.ready(initialize); 
    </script>
  </head>
  <body>
    <div id="map" style="width:100%; height:100%;"/>
  </body>
</html>

There are a few steps to follow in order to initialize a map in your web application:

  1. Setup an HTML document and include esri.css style sheet in the head section of the document to have styles and various widgets for the map.

    <link rel="stylesheet" href="http://geodata.npolar.no/arcgis_js_api/library/3.8/3.8/js/esri/css/esri.css"/>
    
  2. Add reference to the ArcGIS API for Javascript which loads all symbols and definitions needed for using the API.

    <script src="http://geodata.npolar.no/arcgis_js_api/library/3.8/3.8/init.js"></script>
    
  3. Create a div element with a certain id to hold the map. The size of the map is specified in the style attribute of the div.

    <div id="map" style="width:100%; height:100%;"/>
    
  4. Use another <script> tag to load the mapping modules from ArcGIS JavaScript API using the dojo.require() function. The initialize function creates a map instance using the esri.Map module and connects it with the DIV element created above by referencing it using the "map" id.

    <script>
    dojo.require("esri.map");
    function initialize() {
        // create map instance and add a basemap
        var map = new esri.Map("map");
        basemapURL = "http://geodata.npolar.no/arcgis/rest/services/Basisdata/NP_Basiskart_Svalbard_WMTS_25833/MapServerin"
        map.addLayer(new esri.layers.ArcGISTiledMapServiceLayer(basemapURL));
        }

        dojo.ready(initialize); 
    </script>

Add a topographic basemap of Svalbard to the map by providing the cached map service REST URI.

Finally, instruct the API to only execute the initialize() function after dependencies are fully loaded and the DOM is read, by passing dojo.ready().

That's it! You now have a working map of Svalbard.

Map Options

At this stage, you didn't pass any optional parameters when creating the map instance and therefore the map is loaded with the default extent and zoom level.

Because we often want to center the map on a specific area, create an initialExtent object to hold the starting extent of the map and add it to the map instance created above. Use the extent helper to create your desired map extent coordinates in JSON.

    var intialExtent = new esri.geometry.Extent ({
        "Xmin": 477423.89,
        "Ymin": 8663685.98,
        "Xmax": 553624.05,
        "Ymax": 8714486.09,
        "spatialReference": {"wkid":25833}
        });
    // create map instance and add a basemap
    var map = new esri.Map("map" {extent: initialExtent});

By default the Esri logo is drawn to the bottom right of the map which can be turned off by:

 var map = new esri.Map("map" {extent: initialExtent, logo: false});

Geocoding Service (Search place name)

Norwegian Polar Institute provides the place names API for looking up place names dynamically from user input. The search results can be used to convert place names (e.g "Longyearbyen") into geographic coordinates (e.g. latitude 78.22223 and longitude 15.631533), which you can use to place markers or position the map.

Autocomplete place names

The YUI autocomplete library is used to dynamically search for place names as the user types in the input field. As text is entered, the autocomplete returns place name predictions to the application in the form of a drop-down pick list which can be used to help users find and zoom to a specific location.

Requirements: Make sure you add reference the YUI library before creating the autocomplete instance.

<script src="http://yui.yahooapis.com/3.10.1/build/yui/yui-min.js"></script>

Next, create a new YUI instance for your application and populate it with the required modules by specifying them as arguments to the YUI().use() method.

<script>
// Create a new YUI instance and populate it with the required modules.
YUI().use("autocomplete", "autocomplete-filters", "autocomplete-highlighters", function(Y) {
    // AutoComplete is available and ready for use. Add implementation code here.
});
</script>

You can use the placenames API within your code as results source via the http://placenames.npolar.no:80 URL. The results source contains the input terms and a callback method to execute upon receipt of the response.

The JSON response is an object in the following form:

{
location: "Svalbard",
title: "Longyearbyen",
terrain: "Bustad",
approved: true,
ident: "8560",
north: 78.22223,
link: "/stadnamn/Longyearbyen?ident=8560",
east: 15.631533,
newer_ident: ""
}

The fields are explained in the place names API. These fields can also be passed as parameter to narrow the search results.

The example below restricts your autocomplete results to place names that are approved and within Svalbard:

<script>
    // Create a new YUI instance and populate it with the required modules.
    YUI().use("autocomplete", "autocomplete-filters", "autocomplete-highlighters", function(Y) {
        // Add the yui3-skin-sam class to the body so the default
        // AutoComplete widget CSS skin will be applied to the form element.
        Y.one('form').addClass('yui3-skin-sam'); //Autocomplete css

        var geoname_base = "http://placenames.npolar.no:80";
        // Geoname service URI (JSONP service)
        // Use GET parameters ?location= and ?approved=true|false to change service URI
        // and thereby restricting results, e.g. /stadnamn/auto?location=Svalbard&approved=true
        var geoname_service = geoname_base + "/stadnamn/edge/{query}?callback={callback}&rows=5" + "&approved=true&location=Svalbard⟨=nn";
        var geoname_autocomplete = Y.one('#geoname_autocomplete');
        geoname_autocomplete.plug(Y.Plugin.AutoComplete, {
            resultHighlighter : 'phraseMatch',
            //resultFormatter: simple_geoname_formatter,
            resultTextLocator : 'title',
            source : geoname_service
        });

        // zoom and add marker to the map when the user selects a place name from result 
        geoname_autocomplete.ac.on('select', function(e) {
            //console.log(e.result.raw);
            WGS84ToUTM33(e);
            addMarker(position);
        })
    }); 
    </script>

The last function zooms and adds a graphic marker to the map when a user selects a place name from the result.

Finally, create a div element above the map div to hold the search form and add an input element with the geoname_autocomplete id referenced in the YUI instance.

    <div id = "search" style="margin:10px 10% 0 10%; position: absolute; width: 250px; z-index: 2;">
        <form action="" method="get">
            <input type="search" id="geoname_autocomplete" value="" placeholder="Zoom to place name"/>
        </form>
    </div>

Map Overlays

Adding Graphics

The ArcGIS JavaScript API also alows to add or draw graphics such as markers, polylines, polygons, and popups into your map. Those objects have location coordinates tied to them so that they can move when zooming or panning the map.

You can create and add a point, polyline, or polygon using the esri.Graphic object.

When adding graphics to the map, you need to wait for the map to load first. This can be done by adding a function that runs after the map finishes loading using the dojo.connect() event handler. The example below adds a simple point around Longyearbyen where the geometry is set using esri.geometry.Point(). The coordinates used to create the point geometry in this sample are in UTM33.

<script>
    dojo.require("esri.map");
    function initialize() {
        // create map instance and add a basemap
        var map = new esri.Map("map", {logo : false});
        basemapURL = "http://geodata.npolar.no/ArcGIS/rest/services/Basisdata/NP_Basiskart_Svalbard_WMTS_25833/MapServer"
        map.addLayer(new esri.layers.ArcGISTiledMapServiceLayer(basemapURL));

        dojo.connect(map, 'onLoad', function() {
            var symbol = new esri.symbol.SimpleMarkerSymbol().setColor(new dojo.Color([255, 0, 0, 0.5]));
            var graphic = new esri.Graphic(new esri.geometry.Point(514589.2466, 8682916.3628), symbol);
            map.graphics.add(graphic);
            }); 
        }
        dojo.ready(initialize); 
    </script>

Similar method can be used to create lines, polylines, and polygons.

Drawing on map

If you would like the users to draw a points, lines, or polygons on the screen and capture that geometry, the easiest is to use Draw toolbar of ArCGIS API for Javascript.

Map Service Layers

Norwegian Polar Institute provides various dynamic thematic map services that can easily be overlayed on the top basemaps. You can use the map Services Directory to discover the available map services. \ Dynamic map services are more flexible than cached services by providing the user options such as turn on and off layers in the service, change layer transparency, freely adjust the scale, retrieve layer info and legend, etc.

To create dynamic layer to a map, you only need to call the esri.layers.ArcGISDynamicMapServiceLayer() constructor pointing to the URL of service's REST endpoint (e.g. http://geodata.npolar.no/ArcGIS/rest/services/inspire3/Sjofuglkolonier/MapServer).

//Use the ImageParameters to set the visible layers in the map service during ArcGISDynamicMapServiceLayer construction.
    var imageParameters = new esri.layers.ImageParameters();
    imageParameters.format = "png32";  //sets the image format to PNG32.
    imageParameters.layerIds = [0]; // we want the layer with id 0 to be visible
    imageParameters.layerOption = esri.layers.ImageParameters.LAYER_OPTION_SHOW;
    //Takes a URL to a dynamic map service.
    serviceURL = "http://geodata.npolar.no/ArcGIS/rest/services/inspire3/Sjofuglkolonier/MapServer";
    var dynamicLayer = new esri.layers.ArcGISDynamicMapServiceLayer(serviceURL, {
          "opacity":0.75, 
          "imageParameters":imageParameters
        });              
    map.addLayer(dynamicLayer);

The above code creates a layer from a dynamic ArcGIS Server map service. The following arguments were passed to the ArcGISDynamicMapServiceLayer constructor in order to create the layer:

  • The URL of the map service. The URL provided in this sample is the Seabird colonies map of Svalbard.
  • Optional parameters to specify the image format (png, jpg, png32 etc).
  • An opacity setting that determines the transparency of the layer which is between 0 and 1.

Finally, you need to add that dynamic layer on top of the basemap by calling the map's addLayer() method.


Norwegian Polar Data

Norwegian Polar Institute

9296 Tromsø,

Norway