Hawaii Pacific GIS Conference 2012: Internet GIS - Create Your Own Google Like Maps

Create Your Own Google-like Maps
Michael Baker
Senior Consultant

Thursday, September 2, 2010

Why Build a Google-like Mapping Application?

 Have you ever:
– Wanted your mapping application to have the same navigation as Google Maps?
– Wanted the same speed and performance as Google Maps?
– Wanted to see your vector data in Google Maps?
– Wanted to see your imagery in Google Maps?

Thursday, September 2, 2010 2

History of Web Mapping: Pre - 2003

History of Maps on the Web (2003)
The Natio nal A tlas o f
TerraServer USA
Canada

Flash P layer 5
Java 1.0

B irth o f the WWW SVG 1.0
M apQuest
First web bro wser A uto desk's M apGuide

1989 1991 1993 1995 1997 1999 2001 2003
Xero x P A RC M apserver

ESRI's A rcIM S 3.0
Intergraph's Geo M edia
HTM L 1.0
HTTP 1.0 WebM ap 1 .0

Netscape bro wser
ESRI's M ap Objects
(M o saic)


History of Web Mapping: 2003 – Present

Maps on the Web 2003 to Present
SVG 1.2
Yaho o ! M aps A P I

Go o gle M aps

Go o gle M aps A P I

2003 2004 2005 2006 2007
Firefo x 1 (native SVG)
.5
Go o gle Earth

Windo ws Live Lo cal

Term Web 2.0 intro duced


How Does Google Maps Work?


Development History of Google Maps

 Google Maps first started as a software application developed by Lars and Jens Rasmussen
for the company Where2.
 In October 2004 the company was acquired by Google where it transformed into the web
application Google Maps.
 The application was first announced on the Google Blog on February 8, 2005.
 It originally only supported users of Internet Explorer and Mozilla web browsers, but support
for Opera and Safari was added on February 25, 2005.
 Currently Internet Explorer 6.0+, Firefox 2.0+, Safari 3.1+, and Google Chrome are supported.
 It was in beta for six months before becoming part of Google Local on October 6, 2005.


Performance - It Is All About the Cache!

 The map within Google Maps consist as a set of tiles
 These tiles cover the entire earth at each zoom level
 Tiles exist for each map type:
– Street map
– Satellite map
– Hybrid map
– Physical map


How Much Cache?

 Tiles do not cover all regions at all zoom levels
 Different areas of the map may contain tiles at varying resolutions and therefore varying zoom
levels
 Tile coverage of any map type varies based on location
– For example, many areas of the Pacific Ocean do not appear at high zoom levels, while Honolulu may
have very detailed maps


Zoom Levels

 At the lowest zoom level (0), one tile represents the entire earth
 Each succeeding zoom level divides the map into 4N tiles, where N refers to the zoom level
– Zoom level 1, divides the world up into a 2x2 grid for a total of 4 tiles
– Zoom level 2, divides up the world into a 4x4 grid for a total of 16 tiles


Spherical Mercator

 The coordinates in Google Maps and which are presented to the users is Latitude/Longitude
in WGS84 Datum
 For tile publishing, a Mercator projection is used.
 Why Mercator?
– Mercator projection significantly distorts scale and area
– It has two important properties:
 It is a conformal projection
– Preserves the shape of relatively small objects
 It is a cylindrical projection
– North and south are always straight up and down, and west and east are always straight left and
right
 Since the Mercator projection goes to infinity at the poles, it does not actually show the entire
world.
– Maximum latitude is approximately 85.05 degrees


Addressing Tiles

 There are three coordinate systems that Google uses:
– Pixel coordinate referencing a point on an image tile
– Tile coordinates referencing a tile within a tile layer
– The zoom layer, which defines the total number of tiles
 This is often referred to as Google XYZ


Why Would You Not Use Google?

 Why as a website developer, who controls all aspects of your site, would you allow a big alien
blob on your site?
– You accept whatever colors, fonts and map layers Google chooses
– You do add some custom markers and overlays but fundamentally, the map itself is out of your hands
 Google’s choices about what to display on the map may not work for your application
 You are limited to Google API’s terms and conditions
 You are limited to what Google wants to implement
 You so have much invested in your data


If Not Google Maps, What?

 The key is to understand the map
stack
 Modern online mapping applications
Browser UI
adhere to this architecture
HTTP Server
 There are four major components of
the map stack:
– Browser UI
– Tile Cache
Tile Cache
– Map Server
– Geospatial data Tile Server

Map Server

Geospatial
Data
Application Server


Tile Cache

 A tile cache is a server that sits between the browser and the map server.
 It checks to see if a requested map tile is already generated so it can be served up quickly.
 If the map tile is not already generated, the tile cache gets it from the map server and saves it
for future requests.
 The tile cache may be considered as one half of a layer in the map stack.
 It is not technically required.


Map Server

 A map server is an application that takes geospatial data as input and renders graphical
output.
 The map server allows the user creative control of the final map.
 Map servers can be exposed directly to the internet or can be hidden from direct access by
the tile cache layer in the stack.


Geospatial Data

 The building blocks of any mapping application are the databases that define the points, lines,
and polygons that represent real-world places, roads, and areas.


How Do I Create a Google Maps-like Application


Performance – Need Cache

 Map caching is a very effective way to make maps run faster.
 When you create a map cache, the server draws the entire map at several different scales,
and stores copies of the map images.
 The server can then distribute these images whenever someone asks for a map.


Tile Caching Review

 Advantages
– Performance
– Quality
 Performance isn’t affected by how much detail is on the map
– Industry standard
 Tile caching is becoming an industry standard
 Disadvantages
– Takes time to generate the tiles
 When should you cache?
– If the data you see on the map needs to be live, with no time delay acceptable, then caching is not
appropriate.
 Although the cache represent pictures of the data, you can still run operations on your map
and your data.
 These operations will query the server and return the results.
 Results will be drawn on top of the cached image.


Thinking about Cache

 Need to think about the layers of the map
 Design your map for the scale to be viewed.
 Utilize the style properties at each scale.
 Choose your largest scale carefully. This will show the most detail and take the longest to
process.


Utilize Open Source Tools

 Remember the map stack
– Browser UI
– Tile Cache
Browser UI
– Web Server
– Geospatial Data HTTP Server

 There are a couple of commercial /
open source tile caching solutions
Tile Cache

Tile Server

Web Server

Geospatial
Data
Application Server


Summary

 Google Maps is a great application. However, it has limitations.
 Organizations have spent a tremendous amount of money collecting and maintaining their
data.
 It is not difficult to create your own Google-like mapping application.
 The key is to understand the elements of the map stack.
 Remember scale and layer definitions.


Questions?


Hawaii Pacific GIS Conference 2012: Internet GIS - Create Your Own Google Like Maps

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