GIS 2096
Introduction to Web Mapping
&
The WWW
Google Maps
& Google Mashups
The World Wide Web
• Clients
• Servers
• Communication Networks
Server
Client
Clients
• Applications that run on computers
• Rely on servers for
– Files
– Devices
– Processing power
• Examples:
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E-mail
Web Browser
FTP
ArcMap, QGIS
Clients are Applications
Servers
• Computers or processes that manage network
resources
– Disk drives (file servers)
– Printers (print servers)
– Web content (network servers)
Servers Manage Resources
• Example: Database Server
– A computer system that processes database
queries
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 Earth
Differences and similarities
• Google Maps & MyMaps
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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
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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 Earth
Which 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.
Web Mashup Definitions
• Mashup: A web application that performs browserside integration of content or services from multiple
sources
• Provider: site the provides content to the mashup
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Markup languages
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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.
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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 page
The Body section:
Where you put most of your content
Javascript
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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
GoogleMaps use javascript to call the Google
server and to provide specific parameters for your
mashup
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.
Google Map Code
Google Resources
Google Maps API Sign Up
http://code.google.com/apis/maps/signup.html
Google Maps API Documentation
http://code.google.com/apis/maps/documentation/introduction.html
Google App Engine
http://code.google.com/appengine/
Google Map Books
http://www.googlemapsbook.com/
Map Builder
http://www.mapbuilder.net/
Mashup Examples
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housingmaps.com
Wii Finder
Clockr
popurls.com
Yahoo vs. Google
Google Gadgets
35
Lab 6
Open Firefox
Go to http://maps.cga.harvard.edu
Click on Google Maps tutorials