19 January 2016

The main requirement of this project is to be implementing a reality application based on time difference of arrival. Create, develop and make use of the tool to enhance human convenience.  
Thus, it need to design a positioning system. 
In this system, it may include L
1. receiver module 
2. transmitter module
3. MCU or computer to do calculation

To find the position, it can need a shape signal pluse in different media, for example, sound, ultrasonic, light and radio.

The speed of sound: 343.2 m/s, Ultrasonic will transmit in 343.2 m/s.
The speed of light: 3 x 10⁸ m/s. Radio waves will travel at the speed of light
For speed different, I will choose sound to be media in order to reduce positioning error.


In this stage, I still to find hardware unit to receive signal pulse,
The first attract thing is to record the audio signal and transform to computer. It may use USB Microphone for further experiment.

12 January 2016

Thank for dr. martin chow, I had learnt the early positioning system based on TDOA technique such as Loran-C and OMEGA Navigation System. 

Loran-C is the radio navigation system for use on merchant ships. Generally, it seems to be a “Start” pulse when the master signal is revived. Then, it is a “Stop” signal when the secondary transmitter signal received. The time difference from “Start” to “Stop” is a constant. Based on the constant time difference value, it can plot a hyperbolic curve between signals from two stations. The position can be found by more hyperbolic.

OMEGA is the first radio navigation system in global-range and  need to use atomic clocks for synchronizing. Omega used to determine the transition time between transmitter and receiver. Then, it use hyperbolic geometry to find the target position.