GIS 2096

Introduction to Web Mapping&

The WWWGoogle Maps

& Google Mashups

The World Wide Web

• Clients• Servers• Communication Networks

Client

Server

• Applications that run on computers• Rely on servers for

– Files– Devices– Processing power

• Examples:– E-mail– Web Browser– FTP– ArcMap, QGIS

Clients

Clients are Applications

Servers

• Computers or processes that manage network resources– Disk drives (file servers)– Printers (print servers)– Web content (network servers)

• Example: Database Server– A computer system that processes database

queries

Servers Manage Resources

Client–Server Relationship

Process takes place on the server and the client

• Servers– Store and protect data– Process requests from clients

• Clients– Make requests– Format data on the desktop

Client-Server Computing Optimizes Computing Resources

What is a Google Map?Maps.google.com - interactive street, satellite, terrain maps and more.

What is Google Maps?An enormous amount of searchable geographic information (gazetteer)

A way of organizing the worlds information geographically

What is a Google Map?Google MyMaps – customize maps with user created enhancements.

Is Google Maps FOSS?• No• It is free of charge

What is Google Maps - summary• A web mapping service, free for non-commercial use

that contains:– Detailed global basemaps: streets, satellite imagery, and

terrain.– Useful services such as address and place locating by

searching against an information rich gazetteer.– Ability to overlay a wide variety of map layers, (weather,

traffic) from static or dynamic sources.– Map layer creation and light customization through

functionality through MyMaps.– An API that allows for embedding and extensive

customization.

Application Programming Interface (API)

• API - An interface to a software program that allows users to interact and customize it.– Determines the vocabulary and calling conventions a

programmer uses to employ the software services.– Usually based on an existing programming languages

(C, .NET, VisualBasic, Java, javascript)– Many desktop and web software applications have API’s– Google Maps API uses javascript

Google Maps API• Allows embedding of a Google map into one’s own web

page using javascript.

• Free to use, on any website that is provided free of charge to others.

• Relatively gentle learning curve.

• Highly customizable and easily transferrable.

• Evolving - new functionality consistently being added.

What is a Mashup• A web page or application that combines data or

functionality from two or more external sources to create a new service.

Therefore:MyWebPage + Google Map = mashup

Even better:MyWebPage + Google Map + Other web service(s)

Google Map mashups examples: embeddable and customizable

Google Maps, Mashups, and Google EarthDifferences and similarities

• Google Maps & MyMaps– A free web application (no software installation necessary)– 2 dimensional map view, with street, satellite, terrain basemaps– Data creation possible (points, lines, polygons), reads limited kml.– A selected set of map overlays and functions available.– Specific maps can be saved and shared easily on the web.

• Google Maps Mashups– A free service allowing one to embed a Google Map into a web page.– 2 dimensional map view, with street, satellite, terrain basemaps.– Highly customizable to include everything in MyMaps and more.– Customization requires using javascript and HTML.– Requires access to a web-server to publish to the web.

• Google Earth– A free desktop application (downloading and installation necessary).– 3 dimensional map view with satellite basemap, many map overlay layers, and a rich set

of visualization tools.– Data creation possible (points, lines, polygons).– Complex kml creation is possible.

Google Maps, Mashups, and Google EarthWhich one to use?

• Google Maps– Locating, measuring, or learning about the geography of a place.– If you want to share a map.– Communicate geographic information quickly.

• Google Maps Mashups– Used to embed a map into a new or existing website.– Create interactive web maps for your users.

• Google Earth– Visualizing terrain, 3d buildings, historical imagery, and access to many

thematic map layers.– Virtual tour creation (movies)– Small amounts of data collection, geocoding, and image geo-referencing.

Axioms to follow for fledgling Google mappers

• If MyMaps or an existing mashup can be used to accomplish your web mapping goal, use it.

• In your internet browser, use “View > Page Source” to learn what code is used to produce a specific website.

• When coding, pay attention to every character.

• Comment your code thoroughly.

• Organize, document, and backup your maps and data.

• Other web map mashup API’s exist (Yahoo!, Microsoft, OpenLayers). If Google’s API doesn’t serve your needs, explore the others.

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Web Mashup Definitions

• Mashup: A web application that performs browser-side integration of content or services from multiple sources

• Provider: site the provides content to the mashup

Markup languages Markup languages –

• Hyper Text Markup Language (HTML), Extensible Markup Language (XML), Keyhole Markup Language (KML), and many more…

• Text encoding schemes used to create and format a web document.• Use tags contained within brackets <> to define formatting that web

browsers read.

Markup language code sample:

<html><body><p><b>This a new paragraph of text that is bold</b></p><p><big>This text is new paragraph of text that is big</big></p><i>This text is italic</i></body></html>

HTML

•HyperText Markup Language

•What you create a web page in

•Consists of specific sections

•Content described by tags

HTML Tags

Syntax<TAG> content </TAG>

Standard Elements<html>...</html> Specifies the type of document<head>...</head> Title, Metadata, Scripts etc.<body>...</body> The main content of the page

Comments<!-- A Comment -->

A Basic HTML Page

<html>

<head> <title> favorites / bookmark title goes here </title></head>

<body bgcolor="white" text="blue">

<h1> My first page </h1>

This is my first web page and I can say anything I want in here - I do that by putting text or images in the body section - where I'm typing right now :)

</body>

</html>

HTML Tags

A Few Common HTML Tags<title>…</title> Web page title – Head section<p>…</p> Paragraph – basic text in Body section<a>…</a> Anchors – hyperlinks<script>...</script> To embed a script – e.g. javascript<table>…</table> Creates a table<tr>…</tr> Creates a table row<td>…</td> Creates and populates a table cell<div>…</div> Divide document into sections

Basics of an HTML page

The Head section:•Where you define the title of your web page•Include metadata for your page so search engines like Google and Yahoo can find your page•Style sheets (CSS) and scripts (javascript)<head><title> Blah blah blah </>title<meta…><script type=“text/javascript”> …</script></head>

Basics of an HTML pageThe Body section:Where you put most of your content

Javascript Javascript: Typically a “client side” programming language used primarily in

web browsers Used to provide dynamic content to a web page

• Uses variables, loops, and functions to generate output on the web.• Allows for the development of enhanced user interfaces and dynamic

websites.

Javascript code sample (Adds a placemark on a Google map)

function createMarker(point,html) {var marker = new GMarker(point);GEvent.addListener(marker, "click", function() { marker.openInfoWindowHtml(html); });return marker; }var point = new GLatLng(35.65654,-106);var marker = createMarker(point,’Info in Window’);gmap.addOverlay(marker);

Javascript<html><head><script type="text/javascript">function message(){alert("This alert box was called with the onload event");}//Comment</script></head>

<body onload="message()">

<p>We usually use the head section for functions (to be sure that the functions are loaded before they are called).</p>

</body></html>

http://www.w3schools.com/JS/JS_examples.asp

Explanations of the Basic Google Maps Code

Google Map Code

This first javascript is a critical script element. It’s src attribute points to the location of the API on Google’s server, and your key is passed as a parameter.

GoogleMaps use javascript to call the Google server and to provide specific parameters for your mashup

Google Map Code

Google Resources

Google Maps API Sign Uphttp://code.google.com/apis/maps/signup.html

Google Maps API Documentationhttp://code.google.com/apis/maps/documentation/introduction.html

Google App Enginehttp://code.google.com/appengine/

Google Map Bookshttp://www.googlemapsbook.com/

Map Builderhttp://www.mapbuilder.net/

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Mashup Examples

• housingmaps.com• Wii Finder• Clockr• popurls.com• Yahoo vs. Google• Google Gadgets

Lab 6

Open FirefoxGo to http://maps.cga.harvard.edu

Click on Google Maps tutorials