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7.4. Develop an X’treme Prototype: Sensing & Analysis Software
105
Figure 7.4: Logging-unit composed of Smart-Its Technology
7.4.2 Data-Logging
Due to our positive experience from previous projects
[
Kern and Schiele 2003
]
we
built the sensing platform (see Figure 7.4) upon the Smart-Its platform
[
Holmquist
et al. 2004
]
. It provides computation power through a PIC micro-controller that
can sample analog data with a rate up to 50kHz with a resolution of 10bits. An
add-on multiplexer-board (see
[
Kern and Schiele 2003
]
for details) shares this A/D
conversion among 24 analog input channels for sensor data. The on-board UART
driver of the Smart-It limits the maximum data rate to 14kB/sec. Assuming a the
average logging duration of a ski-run of two minutes and considering one more minute
before and after the run, with the maximal data rate, 2.47MB accumulate. For the
first prototype which chose the simplest way: Two data-logging units connected to
a Laptop-PC via serial line for persistent data storage.
7.4.3 Software: SKI - Synchronous Kinetics Integration
An analysis software prototype, referred to as SKI, was developed, so that video
sequences and data recorded by the sensor platform can be viewed in a synchro-
nized way. During the development of the visualization software one challenge was
to implement an intuitive representation of the measured data. Furthermore, spe-
cial attention was paid towards extensibility, in order to incorporate feedback and
suggestions stemming from users during the experience sessions: By using the Java
Reflection Framework
[
Green 2003
]
new data-viewers derived from basic framework
classes can be added to the software without any further changes of the entire frame-
work. In SKI the user can associate video recordings of a ski with sensor data, and
view those through di erent visualization representations (see Figure 7.5a).
In particular, the framework provides rotating bars indicating rotation movements
primarily for gyroscope data (see Figure 7.5b), a composition of all foot force mea-
surements (see Figure 7.5c), and, finally, an animated data plot showing the plain
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