NL Maps

Table of Contents

• Purpose
• Usage example
• Getting set up
• API documentation
• Events
• Advanced usage
• Raw tile URLs
• Developing

Purpose

The nlmaps JavaScript library allows you to create layers for Leaflet, Google Maps, Mapbox, or OpenLayers pre-configured to use the BRT-Achtergrondkaart layers. You don't need to figure out the tile URLs yourself. To make it even easier, it automatically detects the map library you're using and creates a map pre-loaded with one of the BRT-Achtergrondkaart layers.

Usage example

let map = nlmaps.createMap({style: 'grijs', target: 'nlmaps-holder'});

Available map styles:

• standaard: the default BRT-Achtergrondkaart in color
• pastel: in pastel tints
• grijs: in very low saturation
• luchtfoto: aerial imagery

Extending

In order to create a NL Maps version for your own organisation you can extend upon this package. To see an example of this you can check out the City of Amsterdam's version amaps on GitHub.

Getting set up

Wizard

The NL Maps wizard makes it super easy to get started with your choice of map library and map style. It gives you a code example that shows you how to include the HTML and JavaScript code to get a working map. It is recommended that you refer to the wizard output even if you are doing things manually.

Manual browser configuration

You need one of Leaflet, Google Maps, Mapbox, or OpenLayers available in your web page. nlmaps autodetects which one is present (and currently considers it an error if more than one is present). For further information on using the respective libraries, refer to their documentation:

• Google Maps
• Leaflet
• Mapbox
• OpenLayers

Finally, you will need the nlmaps library itself, which you can download from the latest release on Github. Download and extract the source code and select the file dist/nlmaps.iife.js Include it on your web page like this:

<script src="url_of_nlmaps.iife.js"></script>

NodeJS

nlmaps has been developed against NodeJS version 6.x.

npm install -S nlmaps

//CommonJS
let nlmaps = require('nlmaps');

//ES2015 Modules
import nlmaps from 'nlmaps';

Leaflet, Google Maps, Mapbox, or OpenLayers will also need to be available in your final web browser scope. One way you can do this is to install a package that wraps your map library for Node; in that case npm install -S it (for example, leaflet, google-maps or openlayers). You can also include it as a script in the HTML-file that loads your final app output.

Note on using Mapbox: if you are using the Mapbox library, follow the instructions for Leaflet. Since Mapbox includes the Leaflet library it will work the same.

API documentation

nlmaps.createMap(options<object>)

Creates a map using Leaflet, Google Maps, Mapbox, or OpenLayers with a given BRT-Achtergrondkaart layer already added as a background layer. Configured with an options object with the following properties:

• target: string (required). This is the id of the div in which to create the map.
• center: object (optional). This object contains latitude and longitude properties for setting the initial viewpoint. Defaults to a position near the centre of the Netherlands.
• zoom: number (optional). This is the zoom level at which to initialize the viewpoint. Defaults to 8.
• style: string (optional). This sets the base map style. One of 'standaard', 'pastel', 'grijs' or 'luchtfoto', default 'standaard'.
• marker: boolean or object (optional). Use one of 'true' or 'false' for setting whether or not to show a marker at the location specified by center. Defaults to 'false'. To explicitly set the position of the marker, pass the marker an object with latitude and longitude properties.
• overlay: string (optional). This specifies a map overlay on top of the BRT-Achtergrondkaart or aerial imagery. One of 'drone-no-fly-zones', 'gebouwen', 'gemeenten', 'hoogte', 'percelen' or 'provincies'.
• search: boolean (optional). Use one of 'true' or 'false' for setting whether or not to show the search box for places and addresses. Defaults to 'false'.

Returns a map object.

Example

const opts = {
  style: 'grijs',
  target: 'nlmaps-holder',
  center: {
    longitude: 5.4534,
    latitude: 52.3112
  },
  zoom: 15,
  marker: true,
  overlay: 'hoogte',
  search: true
};
let map = nlmaps.createMap(opts);

nlmaps.geoLocate(map<map object>, options<object>)

Creates a geolocator control and adds it to the map. Clicking on the control will initiate a browser geolocation API request and center the map on the result. The geolocator can also be initialized to perform a geolocation request immediately, without waiting for the user to click on the control.

• map: object map (required). the map that the geolocator control should be added to.
• options object (optional). An object with one allowed property, start: true|false. If set to true, the geolocator is initialized on page load.

Returns a geolocator object. See the nlmaps-geolocator package for more information.

Example

const map = nlmaps.createMap();
const geolocator = nlmaps.geoLocate(map, {start: true})

nlmaps.<leaflet|openlayers>.bgLayer([style<string>]) | nlmaps.googlemaps.bgLayer(map, [style])

Creates a layer for the given library configured to fetch tiles for style tile source, or if style is omitted, for the 'standaard' tilesource. In order to use the nlmaps library in conjunction with Mapbox, select nlmaps.leaflet.

NOTE: for Google Maps, you also need to pass the map object as the first argument (so if you pass a style, also pass map first).

Arguments:

• map: map.object (only for Google Maps). The map to which the layer will be added.
• style: string (optional). Name of tile source to load. One of 'standaard', 'pastel','grijs' or 'luchtfoto'; default 'standaard'.

Returns a layer object.

Example (OpenLayers)

const layer = nlmaps.openlayers.bgLayer();
layer.addLayer(map);

nlmaps.<googlemaps|leaflet|openlayers>.markerLayer([coords<object>])

Creates a layer for the given library configured to position a marker at the location coords. In order to use the nlmaps library in conjunction with Mapbox, select nlmaps.leaflet.

Arguments:

• coords: object (required). This object contains latitude and longitude properties for setting the location of the marker.

Returns a layer object.

Example (Leaflet)

const marker = nlmaps.leaflet.markerLayer({
  longitude: 5.4534,
  latitude: 52.3112
});
marker.addTo(map);

nlmaps.<leaflet|openlayers>.overlayLayer([overlay<string>]) | nlmaps.googlemaps.overlayLayer(map, [overlay])

Creates a layer for the given library configured to fetch tiles for one of the pre-defined overlay map sources. In order to use the nlmaps library in conjunction with Mapbox, select nlmaps.leaflet.

NOTE: for Google Maps, you also need to pass the map object as the first argument (so if you pass an overlay, also pass map first).

Arguments:

• map: map.object (only for Google Maps). The map to which the layer will be added.
• overlay: string (required). Name of map source to load. One of 'drone-no-fly-zones', 'gebouwen', 'gemeenten', 'hoogte', 'percelen' or 'provincies'.

Returns a layer object.

Example (Google Maps)

const overlay = nlmaps.googlemaps.overlayLayer(map, 'drone-no-fly-zones');

nlmaps.<leaflet|openlayers>.overlayLayer([overlay<string>],[endpoint<object>]) | nlmaps.googlemaps.overlayLayer(map, [overlay], [endpoint])

Creates a layer for the given library configured to fetch tiles for a custom overlay Web Mapping Service (WMS). The service must follow the OGC WMS specification and support the Spherical Mercator (EPSG:3857) projection. In order to use the nlmaps library in conjunction with Mapbox, select nlmaps.leaflet.

NOTE: for Google Maps, you also need to pass the map object as the first argument (so if you pass an overlay, also pass map first).

Arguments:

• map: map.object (only for Google Maps). The map to which the layer will be added.
• overlay: string (required). Name of the custom layer.
• endpoint: object (required). This object contains url, layerName, and styleName parameters for specifying the Web Mapping Service (WMS).

Returns a layer object.

Example (OpenLayers)

const endpoint = {
  url: 'https://geodata.nationaalgeoregister.nl/fysischgeografischeregios/ows?',
  layerName: 'fysischgeografischeregios',
  styleName: 'fysischgeografischeregios:fysischgeografischeregios'
};
const overlay = nlmaps.openlayers.overlayLayer('fysisch-geografische-regios', endpoint);
map.addLayer(overlay);

nlmaps.<leaflet|openlayers>.geoLocatorControl(geolocator) | nlmaps.googlemaps.geoLocatorControl(geolocator, map)

Creates a control for the given library which talks to the given geolocator. The control has a very simple interface: click to initiate a geolocation request and have the map be centered on the resulting location. You need to add the control to the map yourself. Arguments:

Arguments:

• geolocator object geolocator (required). The geolocator to which the control should be connected. If you are using this method, you will probably be creating the geolocator yourself with the nlmaps-geolocator package.
• map object map (only for Google Maps). The map with which the control should be associated.

Returns a geolocator control.

Example (Leaflet)

import geoLocator from 'nlmaps-geolocator';
import geoLocatorControl from 'nlmaps-leaflet';
const geolocator = geoLocator();
const control = geoLocatorControl(geolocator);
control.addTo(map);

nlmaps.clickProvider(map)

only Leaflet

creates an event provider for clicks on the map, which can be subscribed to with a listener function or used as input to nlmaps.queryFeatures.

The click events returned are original Leaflet click events

Arguments:

• map object map (required). The map for which to emit click events.

returns an object with a subscribe function which takes as an argument the callback that should handle the events. clickProvider follows the callbag spec so this callback should have the signature callback(type, data) and should expect type to be 1.

Example (Leaflet)

const clicks = nlmaps.clickProvider(map);
function myHandler(type, data) {
  if (type === 1){
    console.log(data)
  }
}
clicks.subscribe(myHandler)

The returned object is itself a callbag so it can be used with other callbags, as is done with nlmaps.queryFeatures.

nlmaps.queryFeatures(clickProvider, baseUrl, requestFormatter, responseFormatter)

creates an interface to query an HTTP API with coordinates from clicks on the map.

Arguments:

• clickProvider object (required). an nlmaps.clickProvider.
• baseUrl string (required). the base url for the API to be queried.
• requestFormatter function(baseUrl, xy) => formattedUrl string (required). A function which receives the base url and an xy object of the format {x: longitude, y: latitude} and must return the url with which to query the external API
• responseFormatter function(response) => anything (required). A function which receives the API response and can be used to handle the response before passing it on.

Returns an object with a subscribe method which can be used to handle the response. This method takes as an argument a function of signature callback(type, data) and should expect type to be 1. The data argument will be an object of signature:

{
    latlng: {
      lat: <latitude>,
      lng: <longitude>
    },
    queryResult: <queryResult> from reponseFormatter
}

Example

const clicks = nlmaps.clickProvider(map);

function requestFormatter(baseUrl, xy) {
  return `${baseUrl}${xy.x},${xy.y}?radius=50`
}

function responseFormatter(res) {
  let filtered = res.results.filter(x => x.hoofdadres === true);
  return filtered.length > 0 ? filtered[0] : null;
}

let featureQuery = nlmaps.queryFeatures(clicks, requestFormatter, responseFormatter)
featureQuery.subscribe(myHandler)

nlmaps.singleMarker(map, popupCreator)

Leaflet only

places a marker on the map. Meant to be used in combination with nlmaps.clickProvider. The default behaviour is to move the marker on every click, and remove the marker when it is clicked. An optional popupCreator function can be passed to specify how to create a popup on the marker.

Arguments:

• map object map (required). The map on which the marker should be placed.
• popuCreator function(data) => htmlElement (optional). A function which receives data and creates a popup based on it. The function should return an html element to be used by Leaflet to create the popup.

returns an function which can be used to subscribe to nlmaps.clickProvider.

Example with default functionality:

const clicks = nlmaps.clickProvider(map);
const singleMarker = nlmaps.singleMarker(map);
clicks.subscribe(singleMarker);

Example with a custom popupCreator. Note that this function is bound to an object with a removeMarker method, allowing you to remove the parent marker from interaction on the popup.

function popupCreator(d) {
  let div = document.createElement('div');
  let button = document.createElement('button');
  let p = document.createElement('p');
  p.innerText = d.responseText;
  div.append(p);
  button.innerHTML = 'remove';
  button.addEventListener('click', this.removeMarker)
  div.append(button);
  return div;
}
const clicks = nlmaps.clickProvider(map);
const singleMarker = nlmaps.singleMarker(map, popupCreator);
clicks.subscribe(singleMarker);

Events

the nlmaps object produces the following events:

• mapclick when the map is clicked. Returns the click event from the underlying map library.
• search-select when the user selects a search result. Returns the lat/lon location of the result and the 'weergavenaam' of the result.

You can subscribe a listener function to these events as follows:

nlmaps.on('event-name', listener)

Advanced usage

If you're already using a mapping library in your project, you can use the library-specific bgLayer(), overlayLayer(), and markerLayer() functions. All you'll need to do first is create a map and set the view. This is what the createMap() function does under the hood, with some default values.

Leaflet

let map = L.map('map').setView( new L.LatLng(52.20936, 5.970745), 10);
let mylayer = nlmaps.leaflet.bgLayer('grijs').addTo(map);
let marker = nlmaps.leaflet.markerLayer({longitude: 5.5, latitude: 52.5}).addTo(map);

OpenLayers

let map = new ol.Map({
  view: new ol.View({
    center: ol.proj.fromLonLat([5.97075, 52.20936]),
    zoom: 10
  }),
  target: 'map'
});
let layer = nlmaps.openlayers.bgLayer();
map.addLayer(layer);
let marker = nlmaps.openlayers.markerLayer(true)
map.addLayer(marker);

Google Maps

Google Maps requires a bit more code, since we have to add our layer to the mapTypes list manually.

let map = new google.maps.Map(document.getElementById('map'), {
  center: {lat: 52.20936, lng: 5.970745},
  zoom: 8
});

let mylayer = nlmaps.googlemaps.bgLayer(map, 'pastel');

//add your map to the available layers
map.mapTypes.set(mylayer.name, mylayer);
//set it as active layer
map.setMapTypeId(mylayer.name);

To comply with Google Maps JavaScript API Terms of Service we will also add a layer switcher control so the standard map is available.

//add control for switching between layers
let mapTypeIds = [mylayer.name, 'roadmap']
map.setOptions({
  mapTypeControl: true,
  mapTypeControlOptions: {
    mapTypeIds: mapTypeIds
  }
});

let overlay = nlmaps.googlemaps.overlayLayer(map, 'drone-no-fly-zones');

let marker = nlmaps.googlemaps.markerLayer({longitude: 5.0, latitude: 52.5});
marker.setMap(map);

Include only your library-specific functions

If you want to save as many bytes as possible, simply include the sub-module for your map library instead of the whole nlmaps package. Each of these modules provides a bgLayer() function which will return a layer for the corresponding map library, a markerLayer() function which will return a marker on the map, and a geoLocatorControl() function which returns a control for the geolocator.

Web browser:

Download the appropriate nlmaps-<maplib>.min.js release Download and extract the source code and select the appropriate file from the dist directory. Upon including the script in your web page, you will have a bgLayer() function available which works with the respective map library. In order to use the nlmaps library in conjunction with Mapbox, select leaflet.

NodeJS:

npm install --save nlmaps-leaflet

//CommonJS
let bgLayer = require('nlmaps-leaflet').bgLayer; //note the use of property off of require
let marker = require('nlmaps-leaflet').markerLayer;

//ES2015
import { bgLayer, markerLayer } from 'nlmaps-leaflet';

These functions can subsequently be used in the same way as the functions from the parent package.

Removing or further manipulating the map or layer

If you want to remove your map object or layer, you can just use the standard method provided by your library. The objects returned from createMap(), bgLayer(), markerLayer(), and overlayLayer() are just standard map and layer objects for the appropriate libraries. For example, Leaflet has a map.remove() function which destroys the map and clears all event listeners.

The geolocator and the geoLocatorControls

You can also use the nlmaps-geolocator package directly instead of calling it with nlmaps.geoLocate. This gives you flexibility to implement your own control. Each of the library-specific sub-packages provides a control which interfaces with the nlmaps-geolocator API, but these are quite simple controls with, at the moment, hard-coded CSS styling. In the future nlmaps may provide a CSS file but for now, if you want to modify the placement, you should provide your own CSS and/or create your own control.

Raw tile URLs

The tile URLs which nlmaps configures for you follow these templates:

For BRT-Achtergrondkaart series:

https://service.pdok.nl/brt/achtergrondkaart/wmts/v2_0/standaard/EPSG:3857/{z}/{x}/{y}.png

For aerial imagery:

https://service.pdok.nl/hwh/luchtfotorgb/wmts/v1_0/Actueel_ortho25/EPSG:3857/{z}/{x}/{y}.jpeg

Developing

See also CONTRIBUTING

Installation/set up

To develop nlmaps, clone the repository and then in the directory run:

lerna bootstrap
npm install

lerna bootstrap symlinks cross-dependencies between the subpackages into each others' node_modules directory so that they can require() or import each other without having to actually download from npmjs.com

General development notes

Development is most stable in Node version 10.x.

There are some issues when trying to call rollup from npm scripts, so there is a set of scripts in scripts/ that should be called directly. The usage is as follows (note that rollup needs to installed as global):

• node scripts/build to build the source from packages/PACKAGE/src into packages/PACKAGE/build
• node scripts/test to run tests in packages/PACKAGE/test -- runs unit-test.js with Node and copies/compiles browser test js and html to build.
• node scripts/serve to run live-reload servers watching build, for use with the test html pages.
• node scripts/serve-dev to build, test and serve.
• node scripts/publish doesn't actually publish, but copies the build output to the top-level dist/ directory.

All the above scripts can either operate on all subpackages (the default), or on a subset of packages by using the -p flag:

//only builds nlmaps-leaflet and nlmaps-openlayers
node scripts/build -p leaflet,openlayers

The list of packages to consider is specified in scripts/conf.json.

The scripts can be run in watch mode to recompile/retest when source/test files change:

//build leaflet, and rebuild on source file changes
node scripts/build --watch -p leaflet

This is not applicable to the serve script, which always live-reloads.

You can use the wrapper serve-dev to run the whole development setup, but note that all logging will go to one terminal and may be out of order, making it difficult to interpret. You may therefore want to run different combinations of commands for different subpackages in separate terminals for clarity.

Note on testing: The test script looks for a file called 'unit-test.js' to execute; this is meant for testing in nodejs. For the browser, it copies everything matching the glob *test.html to the build dir; and for the actual test scripts, it calls rollup with rollup.test.js as the config file for each package. These currently use browser-test.js as the main entrypoint.

Also, NOTE: the live server runs with basic SSL. You have to open the test pages with https:// or they won't work. You will also need to add an exception for the self-signed security certificates the first time you open them.

Publishing

Lerna is used for optimising the workflow around managing multi-package JavaScript projects with git and npm. Because of some seeming subtleties of Rollup's interaction with Lerna or NPM, there is a different build script. Use the following procedure to publish the packages.

1. lerna exec npm -- install If you need to update dependencies
2. node scripts/build can't use npm run or lerna run because rollup can't handle non-externalized dependencies when lerna is symlinking them.
3. node scripts/publish this doesn't actually publish yet, but copies the transpiled output from packages/*/build/ to the top-level dist/ directory.
4. git add and commit
5. lerna version to choose version numbers for each changed package.
6. lerna publish to publish to the NPM repository.

This publishes to npm as well as creates new git tags for the releases, which are pushed to Github. To finish the release, go to the Github repo's release page and annotate the latest release for the 'nlmaps' package (this makes it show up under the 'latest' path on Github).

Note: publishing usually happens automatically via CircleCI.

Building the webpage

To build the webpage goto the docs folder and make sure you have gulp installed.

Run gulp build to start the build process. When the process is finished the compiled website and assets are available in the build folder.

Note: the gulp build process copies nlmaps css and assets directly from ../packages/assets.