Geolocation and Mapping

GeolocationGeolocation&

MappingIvano MalavoltaIvano Malavolta

[email protected]

http://www.di.univaq.it/malavolta

Roadmap

• Introduction• Geolocation• Geolocation• Google Maps Services*

* In this lecture we refer to Google Maps Services only because of spacelimitations. Other services, like Yahoo! Place Finder, can be used as validalternatives

Geolocation

GeolocationGeolocationGeolocationGeolocation is the identification of the real-world geographic location of an object, like

• mobile phone• Internet-connected computer terminal• Internet-connected computer terminal

Geolocation may refer to the practice of assessing the location, or to the actual assessed location

Mapping

MappingMappingMappingMapping usually refers to map-making and often used instead of cartography

Geolocation VS Mapping

GeolocationGeolocationGeolocationGeolocation refers to geospatial data collection and manipulationdata collection and manipulation

ex. LatLon calculations, geocoding, etc.

Mapping Mapping Mapping Mapping refers to the activity of creating a map through some creating a map through some cartographic works

ex. maps, layers, markers, routes, etc.

Roadmap


* In this lecture we refer to Google Maps Services only because of their high understandability and stability. Other services, like Yahoo! Place Finder, can be used as valid alternatives

Geolocation

navigator.geolocation

Provides access for capturing location information for the device, like:

• latitudelatitudelatitudelatitude

• longitudelongitudelongitudelongitude

• SpeedSpeedSpeedSpeed

Geolocation

The API itself is agnostic of the underlying location information sourcesinformation sources

Common sources of location information include

• Global Positioning System (GPS)Global Positioning System (GPS)Global Positioning System (GPS)Global Positioning System (GPS)

• location info from IP address, RFID, location info from IP address, RFID, location info from IP address, RFID, location info from IP address, RFID, WiFi,GSMWiFi,GSMWiFi,GSMWiFi,GSMcell IDs, etc.cell IDs, etc.cell IDs, etc.cell IDs, etc.cell IDs, etc.cell IDs, etc.cell IDs, etc.cell IDs, etc.

No guarantee is given that the API returns the device's actual location

Geolocation Methods

The geolocation object provides 3 methods:

• geolocation.getCurrentPositiongeolocation.getCurrentPositiongeolocation.getCurrentPositiongeolocation.getCurrentPosition

• geolocation.watchPositiongeolocation.watchPositiongeolocation.watchPositiongeolocation.watchPosition

• geolocation.clearWatchgeolocation.clearWatchgeolocation.clearWatchgeolocation.clearWatch

getCurrentPosition

It returns the device's current position

getCurrentPosition(win, [fail], [options]);

winwinwinwin

callback function with a PositionPositionPositionPosition parameter

failfailfailfail

error callback

optionsoptionsoptionsoptions

geolocation options

watchPosition

It gets the device's position when a change in position has been detectedbeen detected

var id = watchPosition(win, [fail], [options]);

winwinwinwincallback function with a PositionPositionPositionPosition parametercallback function with a PositionPositionPositionPosition parameter

failfailfailfailerror callback

optionsoptionsoptionsoptionsgeolocation options

clearWatch

Stop watching the Geolocation referenced by the watch ID parameterwatch ID parameter

clearWatch(watchID);

watchIDwatchIDwatchIDwatchID

ID returned by geolocation.watchPositionID returned by geolocation.watchPosition

Options

• frequency frequency frequency frequency (Number)– How often to retrieve the position in milliseconds– How often to retrieve the position in milliseconds

• enableHighAccuracyenableHighAccuracyenableHighAccuracyenableHighAccuracy (Boolean)– Receive the best possible results

• timeouttimeouttimeouttimeout (Number)– The maximum length of time (msec) that is allowed to pass from the call until the corresponding callback is invokedfrom the call until the corresponding callback is invoked

• maximumAgemaximumAgemaximumAgemaximumAge (Number)– Accept a cached position whose age is no greater than the specified time in milliseconds

The Position object

Contains the data created by the geolocation API

It is passed as argument to the success callbacks ofgetCurrentPosition and watchPosition

Properties:Properties:Properties:Properties:

coordscoordscoordscoords:::: A set of geographic Coordinates

timestamp:timestamp:timestamp:timestamp: Creation timestamp in millisecondsseconds in iOS

The Coordinates object

A set of properties that describe the geographic A set of properties that describe the geographic coordinates of a position

The Coordinates object is created and populated by Cordova, and attached to the Position object


Properties:Properties:Properties:Properties:

• latitudelatitudelatitudelatitude (Number)– Latitude in decimal degrees

• longitudelongitudelongitudelongitude (Number)– Longitude in decimal degrees

• accuracyaccuracyaccuracyaccuracy (Number)– Accuracy level of the latitude and longitude coordinates in meters

http://bit.ly/Ln6AtM


• altitudealtitudealtitudealtitude (Number)– Height of the position in meters above the ellipsoid

null in Android

– Height of the position in meters above the ellipsoid

• altitudeAccuracyaltitudeAccuracyaltitudeAccuracyaltitudeAccuracy (Number)– Accuracy level of the altitude coordinate in meters

http://bit.ly/Ln7V3H


• heading*heading*heading*heading* (Number)– Direction of travel, specified in degrees counting – Direction of travel, specified in degrees counting clockwise relative to the true north

• speedspeedspeedspeed (Number)– Current ground speed of the device, specified in meters per second

The Compass API in Cordova isexclusively dedicated to the

http://bit.ly/LnanXV

exclusively dedicated to the heading property

Position Error

Encapsulates the error code resulting from a failed position capture operationposition capture operation

It contains a prepreprepre----defined error codedefined error codedefined error codedefined error code

PositionError.PERMISSION_DENIED

PositionError.POSITION_UNAVAILABLEPositionError.POSITION_UNAVAILABLE

PositionError.TIMEOUT

Example

var options = { maximumAge: 3000, timeout: 5000,

enableHighAccuracy: true };

navigator.geolocation.watchPosition(win, fail, options);

function win(pos) {

var el = ‘<div>Latitude: ‘ + pos.coords.latitude + '</div>');

el += ‘<div>Longitude: ‘ + pos.coords.longitude + '</div>');

el += ‘<div>timestamp: ‘ + pos.timestamp + '</div>');

$(‘#block’).html(el);

}

function fail(err) {

console.log(err.code);

}

Roadmap


* In this lecture we refer to Google Maps Services only because of their high understandability and stability. Other services, like Yahoo! Place Finder, can be used as valid alternatives

Google Maps API

The Google Maps Javascript API lets you embed Google Maps in your appMaps in your app

The latest version (v3) of this API

is especially designed to be faster faster faster faster

and more applicable to mobilemobilemobilemobile

devicesdevicesdevicesdevices

http://www.cibando.com

Goole Maps API

The API provides a number of utilitiesutilitiesutilitiesutilities for manipulating maps and adding content adding content adding content adding content to the map through a maps and adding content adding content adding content adding content to the map through a variety of services

You can see it like a way to programmatically managemaps on http://maps.google.com

GMaps Basics

google.maps.Map

This object represents a GMaps map

it will contain the maps along with all the otherelements, like markers, polygons, etc.

GMaps Basics

Here is its constructor:

google.maps.Map(htmlElement, options);

• htmlElementhtmlElementhtmlElementhtmlElement– a reference to a HTML element where you want the map to be insertedmap to be inserted

• for example <div id=“map”></div>

• optionsoptionsoptionsoptions– an object literal containing a set of properties

GMaps Basics

The options parameter may have these properties:

• center center center center (google.maps.LatLng)– the center of the map

• zoom zoom zoom zoom (Number)– the initial zoom-level of the map

• mapTypeIdmapTypeIdmapTypeIdmapTypeId (google.maps.MapTypeId)– what kind of map type that would initially be used

– The most common type is google.maps.MapTypeId.ROADMAP

GMaps Basics

• draggabledraggabledraggabledraggable (boolean)– if false, prevents the map from being dragged– if false, prevents the map from being dragged

• minZoomminZoomminZoomminZoom (Number)– the minimum zoom level which will be displayed on the map

• maxZoommaxZoommaxZoommaxZoom (Number)– the maximum zoom level which will be displayed on the map

• zoomControlzoomControlzoomControlzoomControl (boolean)• zoomControlzoomControlzoomControlzoomControl (boolean)– if false, hides the control to zoom in the map

• etc...

The LatLng object

It is a point in geographical coordinates:

• latitude• latitude

• longitude

ex. new google.maps.LatLng(57.8, 14.0);

The LatLngBounds object

It represents a rectangle in geographical coordinates

• south-west• south-west

• north-east

ex. new google.maps.LatLngBounds(

new google.maps.LatLng(57.8, 14.0),

new google.maps.LatLng(57.8, 14.0)

);

contains(pt), intersect(bounds), getCenter(),

union(bounds), etc.

Map Types

You must specifically set an initial map type at this time as welltime as well

mapTypeId: google.maps.MapTypeId.ROADMAP

Supported types:•• ROADMAP

• SATELLITE

• HYBRID

• TERRAIN

Example

// in your JS file

var options = {var options = {

center: new google.maps.LatLng(-34.397, 150.644),

zoom: 8,

mapTypeId: google.maps.MapTypeId.ROADMAP

};

var map = new

google.maps.Map(document.getElementById(“map”),

options);options);

// somewhere in your HTML templates

<div id=“map”></div>

GMaps Events

There are 2 types of events:

• User events– are propagated from the DOM to the Google Maps API

– for example click

• MVC state change notifications• MVC state change notifications– reflect changes in Maps API objects and are named using a property_changed convention

– for example the API will fire a zoom_changed event on a map when the map's zoom level changes

Map Event Listeners

You register for event notifications using the addListener() event handleraddListener() event handler

google.maps.event.addListener(obj, eventname, callback)

• objobjobjobj: the object on which the event can occur– ex. the whole map, a marker, etc.

• eventnameeventnameeventnameeventname: an event to listen for– ex. “click”, “center_changed”, “zoom_changed”, etc.– every objects can respond to different types of events

• callbackcallbackcallbackcallback: function to call when the specified event occurs

DOM Object Events

It allows you to capture events occurred on elementswithin the DOMwithin the DOM

addDOMListener(obj, eventname, callback)

It is similar to addListener, but here obj can be anyelement within the DOMelement within the DOM

Example

var map = new

google.maps.Map(document.getElementById(“map”),

opt);

google.maps.event.addListener(map, 'click',

function(event) {

var marker = new google.maps.Marker({

position: event.latLng,

map: mapmap: map

});

map.setCenter(marker.getPosition());

}

);

GMaps Overlays

Overlays are objects that you “add” on the mapOverlays are objects that you “add” on the mapOverlays are objects that you “add” on the mapOverlays are objects that you “add” on the map, like

• points,• points,

• lines,

• areas,

• collection of other objects

They are tied to latitude/longitude coordinates

� so they move when you drag or zoom the map

http://bit.ly/Lztdac

Types of Overlays in GMaps

• MarkerMarkerMarkerMarker– represent single locations on the map

http://bit.ly/LztJoV

– represent single locations on the map

– can be represented also by an icon

• PolylinePolylinePolylinePolyline– an ordered sequence of locations

– represent lines on the map– represent lines on the map

In this lecture we will focus on markers & polylines only


• PolygonPolygonPolygonPolygon– an ordered sequence of locations– an ordered sequence of locations

– define a region on the map

• MapMapMapMap TypesTypesTypesTypes– represent map layers

– can replace base map tiles– can replace base map tiles

– can be displayed on top of

base map tiles

http://bit.ly/LztFoV

http://www.mapofthedead.com/


• Info Info Info Info WindowWindowWindowWindow– displays content within a popup – displays content within a popup

balloon on top of a map

– linked to a specific location

• Custom Custom Custom Custom OverlayOverlayOverlayOverlay– any DOM element that be– any DOM element that be

positioned on the map

http://bit.ly/LztFoV

Markers

Markers identify locations on the map

Markers are designed to be interactiveMarkers are designed to be interactive

�you can attach event listeners to them

ex. ex. marker = new google.maps.Marker({

// options

});

google.maps.event.addListener(marker, 'click', callback);

Marker Options

The google.maps.Marker constructor takes a single object literal specifying the initial properties of the object literal specifying the initial properties of the marker

• positionpositionpositionposition– LatLng identifying the initial location of the marker

• mapmapmapmap• mapmapmapmap– the Map object on which to place the marker– You can add the marker later by calling setMap() method– You can remove a marker by calling setMap() with null

Marker Options

• animationanimationanimationanimation– google.maps.Animation.DROP– google.maps.Animation.DROP

– google.maps.Animation.BOUNCE

You may initiate an animation on an existing marker by calling setAnimation() on the marker object

• draggabledraggabledraggabledraggable– makes the marker draggable on the map– makes the marker draggable on the map

• iconiconiconicon– used to set a custom icon for the marker– it defines the URL of an image to be used as icon– The Google Maps API will size the icon automatically

Polylines

A Polyline object consists of an array of LatLngs

It creates a series of line segments that connect those locations in an ordered sequence

Similarly to Marker, the constructor of Polylinetakes an object literal containing the optionstakes an object literal containing the options

Also Polyline can react to user events

Polylines Options

• path[]– array of LatLng, one for each point of the polyline– array of LatLng, one for each point of the polyline

• strokeColor– color of the lines in CSS syntax

• strokeOpacity– opacity of the lines as a decimal number between 0 and 1

• strokeWeight• strokeWeight– the weight of the line's stroke in pixels

• editable– boolean, specifies whether users can modify it or not

Example

var map; // the map object, initialization omitted here

var coords = [

new google.maps.LatLng(37.772323, -122.214897),

new google.maps.LatLng(21.291982, -157.821856),

new google.maps.LatLng(-18.142599, 178.431),

new google.maps.LatLng(-27.46758, 153.027892)

];

var polyline = new google.maps.Polyline({var polyline = new google.maps.Polyline({

path: coords,

strokeColor: "#00FF00",

strokeOpacity: 1.0,

strokeWeight: 1

});

flightPath.setMap(map);

GMaps Services

3 are the main services provided by GMaps:

• DirectionsDirectionsDirectionsDirections

• DistanceDistanceDistanceDistance MatrixMatrixMatrixMatrix

• GeocodingGeocodingGeocodingGeocoding

Directions

You can calculate directions (using a variety of methods of transportation) by using the object

google.maps.DirectionsService

This object communicates with Google Maps which receives direction requests and returns computed results

You can1. manage these directions results directly2. use the DirectionsRenderer object to render them

Direction Requests

1. create an object of type DirectionsService2. create a DirectionsRequest object literal containing

the input terms2. create a DirectionsRequest object literal containing

the input terms3. call DirectionsService.route() to initiate a

request to the Directions service4. manage the results via a callback function manageRoute

var dirService = new google.maps.DirectionsService();var dirService = new google.maps.DirectionsService();

var request = {

origin: ”…”,

destination: “…”,travelMode: google.maps.TravelMode.DRIVING

};

dirService.route(request, manageRoute);

Directions Request Properties

Directions Results

When sending a directions request to the DirectionsService, you receive a response consisting of you receive a response consisting of

1. a DirectionsResultDirectionsResultDirectionsResultDirectionsResult object– contains an array of DirectionsRoute object, each of

them representing a route from the origin to destination

2. a status codestatus codestatus codestatus code2. a status codestatus codestatus codestatus code– OK, NOT_FOUND, ZERO_RESULTS, INVALID_REQUEST, etc.

Example of Route

destination

origin

waypoints

steps

http://goo.gl/maps/ZK4H

legs

Routes

It is an object literal with the following fields:

• legslegslegslegs[]: array of DirectionsLeg objects

• waypoint_orderwaypoint_orderwaypoint_orderwaypoint_order[]: indicates the order of waypoints

• overview_pathoverview_pathoverview_pathoverview_path[]: array of LatLngs approximating the path of the resulting directions

• boundsboundsboundsbounds: LatLngBounds containing the route• boundsboundsboundsbounds: LatLngBounds containing the route

• copyrightscopyrightscopyrightscopyrights: text

• warningswarningswarningswarnings: text

Legs


• stepsstepsstepssteps[]: array of DirectionsStep objects

• distancedistancedistancedistance: total distance covered by this leg

• durationdurationdurationduration: total duration of the leg

• start_locationstart_locationstart_locationstart_location: the origin of the leg as LatLng

• end_locationend_locationend_locationend_location: the destination of the leg as LatLng• end_locationend_locationend_locationend_location: the destination of the leg as LatLng

• start_addressstart_addressstart_addressstart_address: the origin of the leg as text

• end_addressend_addressend_addressend_address: the destination of the leg as text

Steps


• instructionsinstructionsinstructionsinstructions: instructions for this step within as text

• distancedistancedistancedistance: total distance covered by this step

• durationdurationdurationduration: total duration of the step

• start_locationstart_locationstart_locationstart_location: the origin of the leg as LatLng

• end_locationend_locationend_locationend_location: the destination of the leg as LatLng• end_locationend_locationend_locationend_location: the destination of the leg as LatLng

Example

http://bit.ly/KtJrUM

Distance Matrix

It is a service to compute

1.1.1.1. travel distancetravel distancetravel distancetravel distance1.1.1.1. travel distancetravel distancetravel distancetravel distance

2.2.2.2. journey durationjourney durationjourney durationjourney duration

between multiple origins and destinations

This service does not return detailed route informationThis service does not return detailed route information

� you need the Directions Service for these

Distance Requests

google.maps.DistanceMatrixService

.getDistanceMatrix(options, callback).getDistanceMatrix(options, callback)

where

• optionsoptionsoptionsoptions– object literals containing origin, destination, travel modes, ...

• callbackcallbackcallbackcallback• callbackcallbackcallbackcallback– the function executed upon response

Distance Request Options

• originsoriginsoriginsorigins– array containing one or more address strings and/or LatLng

• destinationsdestinationsdestinationsdestinations• destinationsdestinationsdestinationsdestinations– array containing one or more address strings and/or LatLng

• travelModetravelModetravelModetravelMode– google.maps.TravelMode.DRIVING– google.maps.TravelMode.WALKING– google.maps.TravelMode.BICYCLING

• unitSystemunitSystemunitSystemunitSystem– google.maps.UnitSystem.METRIC– google.maps.UnitSystem.IMPERIAL

• avoidHighwaysavoidHighwaysavoidHighwaysavoidHighways (boolean)• avoidTollsavoidTollsavoidTollsavoidTolls (boolean)

Distance Responses

A successful call to the Distance Matrix service returns:returns:

• a DistanceMatrixResponse object

• a DistanceMatrixStatus object

These are passed to the callback function you specified in the request

DistanceMatrixResponse

It is an object containing the following properties:

• originAddressesoriginAddressesoriginAddressesoriginAddresses– array containing the locations passed in the origins field

• destinationAddressesdestinationAddressesdestinationAddressesdestinationAddresses– array containing the locations passed in the destinations field

• rowsrowsrowsrows– array of DistanceMatrixResponseRow objects, with each row

corresponding to an origincorresponding to an origin

• elementselementselementselements– are children of rows, and correspond to a pairing of the row's

origin with each destination– They contain status, distance, and duration information for each

origin/destination pair

Example

var origin = “L’Aquila, Italy";

var destination = “London, England";

var service = new google.maps.DistanceMatrixService();

service.getDistanceMatrix({origins: [origin],

destinations: [destination],

travelMode: google.maps.TravelMode.DRIVING,

avoidHighways: false,

avoidTolls: false

}, callback);}, callback);

function callback(response, status) {

if (status == google.maps.DistanceMatrixStatus.OK) {

var t = response.rows[0].elements[0].distance.text;

alert(t);

}

}

Geocoding

It is the process of convertingconvertingconvertingconverting addresses intogeographical coordinatesgeographical coordinates

ex.

“via Vetoio 1, L’Aquila” � 42.362319,13.368514

A geocoder may return more than a resultA geocoder may return more than a result

You can also perform the inverse conversion

� reverse reverse reverse reverse geocodinggeocodinggeocodinggeocoding

Geocoding Requests

var geocoder = google.maps.Geocoder();

geocoder.geocode(options, callback);geocoder.geocode(options, callback);

where• optionsoptionsoptionsoptions (object literal)

– address (String) � geocoding– latLng (LatLng) � reverse geocoding– latLng (LatLng) � reverse geocoding– bounds (LatLngBounds) – region (String)

• see http://www.iana.org/assignments/language-subtag-registry

• callbackcallbackcallbackcallback– the function executed upon response

Geocoding Responses

They are passed to the callback function as a GeocoderResults object

Example

geocoder = new google.maps.Geocoder();

var address = “via Vetoio 1, L’Aquila”;

geocoder.geocode( { 'address': address}, callback);

function callback(results, status) {

if (status == google.maps.GeocoderStatus.OK) {

for(result in results) {

console.log(result.geometry.location);

}

} else {

console.log(status);

}

}

What’s more?

• ControlsControlsControlsControls

– UI elements to allow user interaction with the map– UI elements to allow user interaction with the map

– zoom, Street View, scale, map type

• LayersLayersLayersLayers

– GeoRSS, KML, Fusion Tables, etc.

• MapMapMapMap TypesTypesTypesTypes & & & & StylesStylesStylesStyles (see http://bit.ly/JEA6Nu)

– custom styles, image overlays, etc.– custom styles, image overlays, etc.

• StreetViewStreetViewStreetViewStreetView ServicesServicesServicesServices

• DrawingDrawingDrawingDrawing LibraryLibraryLibraryLibrary

– drawing tools, geometry, etc.

References

https://developers.google.com/maps/documentation/javascript/

Education

Geolocation and Mapping