In-field validation of the accuracy of wearable sensors is desirable since algorithms that perform well in a laboratory setting may not perform as well in real-world use. However, the use cases can be challenging. For example, a foot worn wearable designed to measure foot trajectory should expect to be used in a variety of scenarios ranging from straightforward (running track) to challenging (a woodland area with many undulations). Typically the more challenging the scenario the more difficult it is to get ground truth with conventional systems. We describe a low-cost, highly-portable, point tracking system that can be used where space and infrastructure is limited. The system is built around a pair of commodity video cameras in a stereo setup. We demonstrate how to configure the cameras, a novel technique to approximate shutter synchronisation to sub-frame interval, and we benchmark the system indoors against gold-standard motion capture systems. For a runner 3 m from the cameras we re able to recover their foot trajectory with a mean spatial deviation of 1.7±1.1 cm.
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