1. Geolocation Technology
a) W3C Geolocation
i. Supported System and Browser
Ø Chrome with Gears
Ø Firefox3.5+
Ø Opera10.0+
Ø Safari4.0+
Ø iOS3.0+
Ø Android2.0+
ii. Locate process
iii. Location Result
Ø latitude double
Ø longitude double
Ø altitude double/null
Ø accuracy double/null
Ø altitudeAccuracy double/null
Ø heading double/null
Ø speed double/null
Ø timestamp DOMTimeStamp
b) Google Gears Geolocation
i. Supported OS System and Widget Frameworks
Ø iOS
Ø Google Gears
Ø BlackBerry Device OS 6
Ø BlackBerry Device Software 4.1
Ø Nokia Web Runtime Toolkit
Ø webOS Application Platform
Ø Bondi Widgets 1.0
Ø Torch Mobile Iris Browser
Ø Mozilla Geode
ii. Locate Process
iii. Location Result
Ø latitude double
Ø longitude double
Ø altitude double/null
Ø accuracy double/null
Ø altitudeAccuracy double/null
Ø heading double/null
Ø speed double/null
Ø timestamp DOMTimeStamp
c) IP Geolocation
i. Support Environment
Ø Every browser connected to the network
ii. Locate Process
iii. Location Result
Ø country_code string
Ø country_name string
Ø city string
Ø region string
Ø region_name string
Ø latitude string
Ø longitude string
Ø postal_code string
Ø area_code string
Ø metro_code string
2. Locating Device
Both Google Gears Geolocation and W3C Geolocation has a strategy to select the locating device. GPS is the first choice, WIFI is the second choice, GPRS is the last choice.
a) GPS
GPS is the most accurate device of all. Its accuracy is about 30 meters. And it is the only way to get the altitude data of the location.
b) WIFI
WIFI is the fastest device of all. Its accuracy is about 70 meters.
c) GPRS
GPRS is the slowest device of all. Its accuracy is about 550 meters.
d) IP
IP Geolocation is the last choice to locate the position. It can only locate the city where you are.
3. Others
Actually the system will not calculate the position every time the locating request is sent. A maximum age of location can be set into the request, the maximum age can be n milliseconds. If a location that is get in the last n milliseconds is stored in the system, this location will be returned to the application directly.
4. Advice
Use Google Gears Geolocation technology to develop our product. Firstly, it has packaged many technology in it. Secondly, we can expand other technology into it when we need, so we can customize our geolocation library based on Google Gears Geolocation.