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Accubeacon. Andrew Gans, Spencer Curran, Shreyank Amartya, Alex Fouss, John Bullock. Avalanche Hazards background. Winter backcountry recreation has become increasingly popular. Thousands of skiers and sledders put themselves in dangerous avalanche zones each year

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Andrew Gans, Spencer Curran, Shreyank Amartya, Alex Fouss, John Bullock

avalanche hazards background
Avalanche Hazards background
  • Winter backcountry recreation has become increasingly popular.
  • Thousands of skiers and sledders put themselves in dangerous avalanche zones each year
  • 90% are caused by a victim or someone in their party.

Personal Account of Avalanche Video


avalanche hazards
Avalanche Hazards

include data on life expectancy


avalanche rescue methods
Avalanche Rescue Methods
  • Probe line - A technique used with an abundance of searchers
  • K9 search team - Avalanche dogs are trained to sniff out buried victims
  • Proper Shoveling - There are several methods for fast and swift extractions
  • Air Bag - A backpack air bag that can be deployed when victim triggers an avalanche to prevent being buried.


other innovations
Other Innovations

Use of sensors

1. Knowledge about the state of the victim; survival chances, urgency, vital signs.

2. Orientation of victim in snow

3. Depth of buried victim.

Multiple Buried victim markers

system overview

System Overview

Accubeacon Avalanche Transceiver

statement of purpose
Statement of Purpose

To design a set of avalanche transceivers that can communicate with each other to allow for more accurate pinpointing of buried victims and multiple burial detection



1. 457 kHz RF

Transmits/receives standard 457kHz frequency signal and processes associated RSSI signal

2. ZigBee Wireless

Transmits in the ISM band and uses RSSI or RTOF (round trip time of flight) to get triangulation information

4.User Interface/Data Processing

Provides clear and concise information about the location of burial


processing and user interface subsystem

Processing and User Interface Subsystem

Accubeacon Avalanche Transceivers

processing and user interface
Processing and User Interface
  • Collects data from 457khz and zigbee subsystems
  • Uses data to run required algorithms for multiple burial detection, localization and trilateration
  • Trilateration
  • Localization
  • Multiple Burial Detection
  • Uses distances between three or more searching beacons to determine relative x,y positions of other searchers
  • Requires accurate distance measurement between searching beacons
  • x,y positions of other searchers allows for triangulation using 457khz signal
trilateration process
Trilateration Process

-Localization determines relative position of other searchers

-Trilateration uses localized distance vectors from other searchers to compute buried location

-Buried location presented to searcher via user interface


multiple burial detection
Multiple Burial Detection
  • Use 457khz signal strength from multiple antenna and multiple beacons to determine distance from buried victim(s)
user interface and hardware
User Interface and Hardware
  • Requirements
    • Processor that can run all required algorithms
    • User interface that displays results of algorithms
development board
Development Board

Atmel xmega 256-A3 microcontroller

  • Power Conversion
  • Serial Connectors
  • 4.5V Battery Jack
  • Test Pads
  • USB connector
  • Power and Serial LED's
  • PDI interface for AVR ISP mkii
microcontroller atxmega 256a3u
Microcontroller - ATxmega 256A3U
  • Past experience with Atmel microcontrollers and AVR Studio
  • Can easily switch to a different series of Atmel microcontroller
  • Easily accessible drivers and libraries for different peripherals and modules
  • Can be easily programmed through PDI using Atmel mkii In System Programmer
user interface
User Interface
  • Push Buttons to power on, switch between search and transmit mode
  • LCD module to display the grid and relative positions of the searchers and victims
zigbee wireless subsystem

Zigbee Wireless Subsystem

Accubeacon Avalanche Transceivers

tasks and responsibilities
Tasks and Responsibilities
  • Sends data between searching beacons
  • Detects RTOF/RSSI from received signal to calculate distance
display processing

-Received Signal Packer from Other Searchers

-Distance correlation (RTOF/RSSi)

Transmitted Signal Packet to Other Searchers

ZigBee Modem

Distance Data to Microcontroller

Processing and Display

-Triangulates burial location

-Displays to screen

-Distances between searchers

-Distance/Angle to buried victim

-Mode information


wireless distance measurement
Wireless Distance Measurement

RSSI(Received Signal Strength Indicator)

-RSSI is the measurement of power present in the received radio signal. RSSI is directly proportional the distance as follows

RSSI 10 log (P/Pref)


wireless distance measurement1
Wireless Distance Measurement

Time of Arrival

- Using synchronized clocks and time stamps to record signal travel time

-Travel time can be correlated with distance

-More accurate than RSSI but requires precise timing


wireless packet
Wireless Packet

-Currently we are using XBee libraries to transmit packet arrays amongst other searcher.

-The packet contains the following data

1. Sender's XBee ID

2. 1st RF distance

3. 2nd Searchers RF distance

4. 3rd Searchers RF distance

5. Distance from 3 to 1

6. Distance from 3 to 2

7. Distance from 2 to 1

-Each individual XBee processes this data and extract all relevant data for their own array.

457 khz rf subsystem

457 kHz RF Subsystem

The backbone of avalanche transceivers

the 457 khz subsystem is the bare minimum needed for a working avalanche beacon
The 457 kHz subsystem is the bare minimum needed for a working avalanche beacon
  • Other marketed beacons only have this system.
  • Some beacons use digital signal processing and 3 axis antennas to eliminate false readings
  • No current beacon uses communication with other searchers to correlate information and further eliminate error
457 khz receiver
457 kHz Receiver457 kHz Transmitter

Transmit on

(Oscillators / Filtering)


(device power on)

Ferrite Rod Antenna (2x, orthogonal) Outputs Radiation Pattern

Ferrite Rod Antenna (2x, orthogonal) Determines Orientation

Analog Front End

(Filtering, Multiplexing, A/D)

Directional Information to Microcontroller


(device switched to search mode)


457 khz transmitter level 3
457 kHz Transmitter (Level 3)

Pulsed 457 kHz

457 kHz













Antenna selection



Frequency Divider



RF Choke


457 khz receiver level 3
457 kHz Receiver (Level 3)

Antenna selection

(sync with Tx)

Creates a DC voltage relative to received RF signal strength

457 kHz tunning

Pulsed 457 kHz


Band pass filter






Out to CPU


457 kHz tunning

RF Choke


Using cross-searcher data communication reduces guesswork and ambiguity with ultimate goal of eliminating a coarse search
  • Trilateration (Triangulation)
  • Quick and precise pinpointing of multiple buried victims (even with unintended signal modulation - overlap)
  • Transmit RF signal within margin of error up to current standards (457 kHz ± 80 Hz)
  • Differentiate signals of multiple buried victims
  • Relay analog information to microcontroller when in search mode

Backwards Compatibility

  • Receive RF signals within a large margin of error (457 kHz ± 200 Hz)
    • Covers range of frequencies for 1970's era beacons
  • If all else fails (one searcher, no xbee communication, etc) the transceiver will function as a regular ("digital”) beacon
prototyping testing
Prototyping & Testing

Multiple searcher tests done

  • Differences in signal waveform (BCA Tracker DTS) give signature characteristics based on buried beacon’s orientation
  • Use the differences in signal to communicate between beacons and determine instantaneous location of buried victim
  • This method can be extrapolated for multiple burials
prototyping testing1
Prototyping & Testing

Digital signal processing

  • Differentiate between signal overlap and no signal overlap
  • Smooth out signal modulation when overlapping

More information is needed to reduce degrees of freedom

  • Searcher inputs number of burials
  • Digital compass used to find magnetic north

Antenna 1

Antenna 2

Transmitting Antenna

(Buried Person)

Receiving Antennas Arrangement

(BCA Tracker DTS)

development plan multiple burials
Development Plan (Multiple Burials)
  • Input data into microcontroller
  • Analog voltages converted to sampled digital signal
  • Signal processed using differential algorithms
  • Vectors assigned to signals and output to high-res matrix display
design approach
Design Approach


1. Proof of Theory

2. Rev A. - Proof Of Concept

3. Rev. B

4. Final Rev.


design so far
Design So Far
  • Completed required background research to show that the concept is feasible - Used existing beacon as test platform
  • Incorporated Zigbee wireless:

-data transmission

-distance measurement

  • Algorith Implementation on arduino


current setup
Current Setup
  • Arduino Uno
  • Xbee
    • Point to Point network
    • RSSI -Distance Measurement
  • BCA Tracker Beacon
    • RSSI pulled from 7-Segment Display
  • Allows for easy implementation of algorithms
revision b
Revision B

-First PCB Revision

-Atmel Microcontroller on “development board”

-Multiple Burial Algorithm Implemented

-Lower Level Input from Existing Beacon

-RTOF implementation


revision c final rev
Revision C - Final Rev.

-Integration of our own 457kHz Transceiver

-Finalized Zigbee System

-Finalized Multiple Burial Determination System

-Finalized Processing/Display


scheduling tasks
Scheduling Tasks

Along with our bi-weekly scheduled lab time, we have weekly "scrums" to discuss progress and updates on Monday nights.

We do our best to set up 2 week sprints, in which we set goals and task to accomplish in order to stay on track with our milestone goals.



Applied for UROP and using Personal Funds.


risks and contingencies
Risks and Contingencies
  • RSSI accuracy has not been proven, RTOF should prove to be more accurate, but we have been unsuccessful implementing

2. RF 457 kHz implementation

3. Expandability to function with N searching beacons

4. Multiple Burial Determination



-Current beacon technology is decades old

-Accuracy is going to be our biggest concern and goal

-Through 2-way communication we project to minimize search time to save lives and hopefully carve out a spot in the market not yet realized