Let me describe the background in brief -
We have web applications. The users can fill up forms from anywhere in the world. Some service needs to be physically present to some physical location. How could we know whether the forms have been filled up from a desired physical location or how could we verify if users logged in to the system from office or home?
The solution we thought - is GPS!
I did some studies about some similar services those use GPS information. The 911 emergency service is one of them.
The 911 service in cell phone is an interesting one. There are basically two kinds of solutions available for the cell phone operators - Network assisted location tracking and GPS assisted location tracking.
For the first case, some operator like T-Mobile uses Triangulation method to locate subject when it is seen by 3 transmitting tower. At any given time, 3 towers calculates receiving signal based on time differences and/or angle differences and locates on relative readings.
Other operators, like Sprint supports E911 based on GPS information. A 911 call triggers the phone chip - the GPS coordinates are transmitted along with baseband signal to 911 operator and the nearest Public Safety Answering Point. This feature is built in with all phone made after 2004-05 - I think.
There are other services provided by operators. For example, Sprint offers the TeleNav service. In that case, tracking by private parties require the person whose phone is being tracked to explicitly give permission and monthly charge. And usually client software has to be installed on the phone to provide these kind of services.
For us, the desktop based solution - where a GPS device will be attached to users' computer, a program will be running inside web browser, having Java Runtime Environment installed in the machine, the web browser will collect GPS coordinates from pc's port and send these data along with application data to the servers.
The demo version worked successfully!
Some of the interesting articles I liked can be found here -
http://electronics.howstuffworks.com/gadgets/travel/gps.htm
