To address the need for portable systems to collect high-quality eye movement data for field studies, this paper shows how one might design, test, and validate the spatiotemporal fidelity of a homebrewed eye-tracking system. To assess spatial and temporal precision, we describe three validation tests that quantify the spatial resolution and temporal synchronization of data acquisition. First, because measurement of pursuit eye movements requires a visual motion display, we measured the timing of luminance transitions of several candidate LCD monitors so as to ensure sufficient stimulus fidelity. Second, we measured eye position as human observers (n=20) ran a nine-point calibration in a clinical-grade chin rest, delivering eye-position noise of 0.22 deg (range: 0.09-0.29 deg) and accuracy of 0.97 deg (range: 0.54-1.89 deg). Third, we measured the overall processing delay in the system to be 5.6 ms, accounted for by the response dynamics of our monitor and the duration of one camera frame. The validation methods presented can be used: 1) to ensure that eye-position accuracy and precision are sufficient to support scientific and clinical studies and are not limited by the hardware or software, and 2) the eyetracker, display, and experiment-control software are effectively synchronized.

A novel, autonomous, fully distributed sensor node platform designed and built for a continuous, wide-area surveillance and security system is described. Sensor nodes cooperate to detect and track intruders in the surveilled area. Analysis and simulation of the surveillance system indicates that while considerably more capability is required in many aspects (processing power, memory, latency, communication range, and so on) than is currently available in common "mote" designs, performance, energy consumption, node lifetime, and ease of use are enhanced by this approach. Because higher capability components are used, more careful scheduling and power control software is required to mitigate the impact on energy consumption. A full software suite was developed and instrumented to record true system usage during operation of the surveillance system. Measurements of actual usage have been made on a moderately oversized prototype platform. A second generation platform has been designed based on the measured usage data. The software suite is being ported to this platform. Lifetime of the second generation platform running the demanding surveillance application is expected to be about 90 days on 2 AA batteries (3000mAh at 1.5V). Applications with less stringent requirements should enjoy much longer lifetimes.