Extreme Sensing 2009:
The Tight Rope Walk
The Eight International
Conference on Information Processing in Sensor Networks (IPSN
'09) IPSN '09 will be hosting the Extreme Sensing competition
April 13, 2009. Each team will need to build a sensor system
using 7 sensors or less that can
perform dead reckoning
as people walk along predefined paths through a 10m x 10m
arena. Each team can use up to 5 body
sensors and at most 2 sensors placed in the arena. In
Phase 1, all teams will track conference attendees, estimating
their final position relative to a known starting
position. Results will
be broadcast live during Phase 1, providing each team an
opportunity to discern how the other teams' systems work and how
they might fail. In Phase 2,
this information can be used to prevent the other teams from scoring more
points, as each team gets one
chance to walk through the arena themselves while suited up with
their opponents' sensors. Rules of Play
Each team must build a sensing system that can perform
dead reckoning as people walk through a 10m x 10m arena, which
will be located in the poster/demo session of the
conference. The goal is to estimate the
final position of the person given the initial position. Teams
can use up to 5 body sensors, which may include accelerometers,
gyroscopes, magnetometers, etc. Each team can also setup at
most 2 sensors in or around the arena, but predefined paths must
remain unobstructed for people to walk, as shown in the diagram
below. The predefined paths will
not be revealed until the day of the competition, and will be
marked with tape. Examples of sensors placed
in the arena might include passive infrared motion
sensors, active infrared break beams, ultrasound, dopplar radar,
weights sensors, etc. These sensors can be useful for on-line
calibration of the body sensors. The sensor systems have
three restrictions: 1) no system may have data cables more than
12 inches in length* 2) no system may impede the motion of the
person being sensed, and 3) no system may use more than
7 pixels in total, eg. no cameras with more than 7
pixels, and no more than 7 single-pixel** sensors. Signal
emitters will be permitted, as long as they do not interfere
with other teams' sensors and as long as they do not help the
system emulate more than seven pixels (see below**). Each
time a person walks a path with a team's sensors, that team will
be required to update a server with its current position
estimate at least once per second. The path estimate
will be visualized and projected onto a wall.
Phase 1, between 5-10 volunteers from among the conference attendees
will walk along predefined paths in the arena, while being tracked by
the various teams. Each volunteer will walk the same path for all
teams, and can wear body sensors from multiple teams simultaneously, if
possible. The volunteer must walk along the path, with each foot
landing on the path in front of the other foot, like tight-rope walking
-- i.e. the volunteer cannot veer from the path and cannot walk
backwards. Aside from these restrictions, however, the volunteer
can move the body in any way that he/she chooses. The teams must
be able to outfit each volunteer with sensors in 1 minute or less, and
must put a sign on the volunteer to indicate that he/she is wearing
that team's sensors. Ground truth will be
obtained by entering the path number and a set of team numbers into a computer before the volunteer walks the path. During Phase 1, contestants will not be allowed to enter the arena.
In Phase 2, each team will be
given one chance for a team member to walk a path with every team's
body sensors. The goal of each team is to score points for themselves
without scoring points for competing teams.
The team can choose any of the predefined paths, but must
obey the same rules applied to the volunteers in Phase 1. The
team member must wear all teams' sensors simultaneously, to the extent
possible. If the different teams' sensors cannot be worn
simultaneously, all team members must still walk the same path for all
walking a path in Phase 2, you will be wearing body sensors from
multiple teams, and is unlikely to be able to fool all of them.
Instead, you will need to choose your walking strategies carefully to
fool the teams that are most likely to beat you, given the scores after
Phase 1. The position estimates from each team will be shown live on a
wall projection during Phase 1, as shown in the Figure to the right.
This is an opportunity for each team to discern how the other systems
work, and how they might fail. For example, radar and PIR sensors may
not detect slow moving objects; accelerometers may be fooled by shaking
or jumping, gyroscopes may be fooled by bending sideways, and so on.
This knowledge can then be used during Phase 2 to score points for your
own team but not for the other teams. No competitive strategies are
off-limits, except that all players must walk monotonically forward
along the predefined path. This means that running or jumping to fool
body sensors or spraying baby powder to illuminate laser beams are all
acceptable. Be sure to focus on avoiding the sensors of the team whose
score is closest to yours.
On Game Day, each system must
automatically (ie. no human intervention) report scores to
a scoring server at least once per minute when it is in use. This can be done through the following XML-RPC
Reporting API |
bool report(float X, float Y)
This function can be used to the current position estimate of a particular team.
The units of X and Y should be meters.
This function is provided by the
competition server, for which the URL will be released on Game Day. In
the meantime, the source code of the server is
publicly available for testing. The code includes a XML-RPC server, a
graphical visualization, and sample clients written in both Python and
Java. Because this is a XML-RPC server, teams may call the function from
any language that provides a XML-RPC library, including C, C++, Java,
Perl, and Python, among others. See this simple "How To"
to learn how to use a XML-RPC client in other languages. Teams will use
HTTP authentication with the username and password provided.
To estimate the final position,
teams should assume each path starts at (0,0) and can use a
coordinate system with any orientation, as long as the units of
the X and Y coordinates are meters. Thus, position estimates
will be scored on their magnitude |X,Y| = sqrt(X^2+Y^2). In
other words, position estimates are scored based on how closely
they approximate the displacement of the final position
form the original position. This score requires a team to
differentiate between walking away from the origin and walking
in a circle back to the origin, but does not penalize for the
orientation of the team's coordinate system.
How to Enter
enter, a team must send email to the competition co-chairs Kamin
Whitehouse and Brano Kusy containing the team's name, institutional affiliation, the
players' names, and a rough description of the hardware to be used.
Entries must be received on or before April 5, 2009. The team
should expect a response with the username and password to be used on the
competition day. Email should be sent to:
In the case of any dispute, decisions about
scoring and eligibility will be made by judges on Game Day and will be
final. Contestants who would like to do something that might be the cause
of dispute should ask for clarification of the rules and/or pre-approval
of the hardware and techniques before the April 5 deadline. All rules of
this contest are subject to clarification or change at any time.
* Wireless networks may be used and power cables of any length may be used. One
long data cable (e.g. a serial or USB cable) may be used to connect your sensor
system to a computer. However, no other cables that carry data may be more than 12 inches in length.
The Extreme Sensing Competition organizers anticipate availability of Student Travel Grants to enable increased student participation in the competition. Each grant includes partial reimbursement for registration and travel costs.
- Application Deadline: April 5, 2009
Student selection for the travel grants will be in accordance with the following guidelines:
- Students who have already received another travel grant from an CPSWeek -related conference or workshop should not apply.
- Travel grants will be awarded according to a financial need basis. Students who are well-funded and have ample means of covering their travel should not apply.
How to Apply
Interested student applicants should pay for the registration and attend CPSWeek first . If they are selected to receive the travel award, the travel award should cover partial expense of the students for registration and travel costs .
The student applicant must send an e-mail to
The subject of the e-mail must be XSC TRAVEL GRANT APPLICATION (in uppercase letters). This e-mail must include the student's faculty advisor in the cc list. The e-mail must include the following information:
Is your research funded by an active grant (yes/no) :
If Yes, is the source of funding NSF? (yes/no):
Underrepresented state/institution (yes/no):
Underrepresented/minority student (explain in 2-5 words):
The applications will be examined and ranked. The top applicants will receive award letters (by e-mail) informing them of the acceptance decision. They will then be instructed how to receive partial refunds, which will be issued to the person or institution that covered the initial expenses.
Women and members of
underrepresented groups are particularly encouraged to apply. Applications
from underrepresented groups will be given special consideration. Whereas
most applicants are likely to be graduate students, undergraduates who are
actively involved in systems research projects are also welcome to
Student travel awards are supported by the National Science Foundation under
Grant No. 0936902.
** A single-pixel sensor can be
defined in many ways. As a general guideline, a "pixel" is a sensor input
that is directly mapped to exactly one sensor output, with no logic in
between. In some cases, a single AND or OR gate on binary sensors may be reasonable (in
order to make the sensor bigger, for example). Single-pixel sensors that
emulate multi-pixel sensors through movement
of the sensor, the use of moving mirrors,
etc, will not be acceptable. Similarly, using actuators that help the
sensor emulate a multi-pixel sensor (such as a time synchronized array of
infrared transmitters) will also not be acceptable. Borderline and
questionable hardware should be discussed before the April 5 deadline,
and all hardware is subject to approval by the judging panel on Game