1. NAVI-LIGHT: GPS based Embedded System for Backtracking in Unfamiliar Environments
Ashray Solanki, Antony Pollail, Lovlish Gupta
Undergraduate Students,
Computer Engineering
Advisor: Alex Doboli, Assistant Professor
Electrical and Computer Engineering Department

2. Definitions Backtrack GPS Time-to-first-fix Embedded System
To go back over the course by which one has come
GPS
Global Positioning System (GPS) is a world-wide radio-navigation system formed from a constellation of 24 satellites and their ground stations
Time-to-first-fix
Amount of time it takes the GPS receiver to start producing solutions
Embedded System
A complete computer on a smaller scale which contains a microprocessor, memory, I/O ports and sensors

3. Technical Description
NAVI-LIGHT is an embedded system based, innovative flashlight used for navigation
Primary function is to
record the user’s starting point
trace the path taken
display the path back to the user
NAVI-LIGHT is a compact portable device that can be easily controlled

4. Technical Description
Records the user’s path by choosing between a GPS receiver or digital compass based on the availability of a GPS signal
Implements a software controlled backtracking system for situations in which a GPS module would be ineffective

5. Operating Environment
NAVI-LIGHT is designed to operate under normal weather conditions
Operating temperature is between 0° Celsius and 60° Celsius
Storing temperature is between -40° Celsius and 70° Celsius

6. Design Requirements
Main objective of the design is a navigational tool that displays the path taken by the user
Primary objective combines the design with the integration of a compass sensor, a GPS module and embedded system
Secondary objective involves software programming and debugging to interface the components together

7. Approach and Design
Design and develop a system level diagram of the components necessary for implementing the navigational flashlight
Components were chosen to be of low power consumption and minimal size; allowing them to be embedded in a portable flashlight

8. Assumptions
Vector 2X digital compass has a 2-degree accuracy and must measure the Earth’s field in the plane which is level
The M12 Oncore GPS receiver has a cold time-to-first-fix of no greater than 60 seconds and a positioning accuracy of less than 25 meters

9. Assumptions
Assumed that the user will operate the GPS receiver outdoors and obtain a signal from at least three satellites
Implementing a velocity sensor to measure the user’s exact distance would yield more accurate results in backtracking mode

10. System Design Vector 2X Digital Compass DATA 8 Software for
backtracking and
GPS mode control
SBC1190
Embedded System
+5V
to GPS
Antenna
GPS
Module
TTL to RS232

11. SBC1190 Embedded System Ready-to-run embedded PC 128K RAM, 256K flash
Small PC/104 format and expansion
Two RS232/RS485 COM ports
24 TTL-compatible I/O Lines
5V - only operation

12. Vector 2X Digital Compass
Complete compass module
Easily integrates with embedded systems
Small in size
High accuracy
Ease of calibration
Low power consumption
Low cost

13. M12 Oncore GPS Receiver Ready for software and systems integration
Small in size
Low cost
Quick implementation
Low power consumption
Fast time-to-first-fix

14. Operational Flow Chart
button not pressed
return to
run mode

15. Backtracking Flow Chart
if heading
has changed
if button is
not pressed
Return to Main if button is pressed

16. GPS Flow Chart if button is not pressed
Return to Main if button is pressed

17. Status and Future Plans
Present:
- Interfacing components of design
- Coding software for backtracking and GPS
Future Plans:
- Implement a velocity sensor to calculate distance traveled with a given degree parameter
- Implement a battery pack to make the
NAVI-LIGHT portable