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Abstract

The proliferation of wearable sensors and monitoring technologies has created an urgent need for standardized sensor placement protocols. While existing standards like SENIAM address specific applications, no comprehensive framework spans different sensing modalities and applications. We present a unified sensor placement standard that ensures the reproducibility and transferability of human movement and physiological data across various systems and research domains. Our framework provides precise anatomical landmarks, coordinate systems, and placement protocols with defined precision levels, compatible with existing data-sharing standards such as the Brain Imaging Data Structure (BIDS) and Hierarchical Event Descriptors (HED). This framework aims to enhance data quality, reproducibility, and interoperability in applications ranging from lab-based clinical biomechanics to continuous health monitoring in everyday life.

The Problem: Inconsistent Sensor Placement

Current sensor placement practices suffer from significant variability that directly impacts data quality. Studies have shown that EMG electrode placement variations of just 2-3 cm can lead to signal amplitude changes of up to 50%, while similar effects occur with IMU sensors where placement variations substantially impact measurement accuracy during dynamic movements. This inconsistency becomes even more problematic as we move toward multi-modal sensing systems that combine motion, physiological, and environmental measurements.

The emergence of consumer wearables and large-scale data-sharing initiatives further highlights these limitations. Modern applications often combine multiple sensing modalities—motion, heart rate, temperature, and other physiological parameters—requiring consistent sensor placement for reliable long-term monitoring and meaningful data comparisons across studies.

Our Solution: A Unified Placement Framework

Our framework addresses these challenges through three core components:

1. Comprehensive Anatomical Landmark System

  • Precisely defined, palpable landmarks for reliable identification
  • Standardized coordinate systems for each body segment
  • Clear relationships between local and global reference frames

2. Quantified Precision Levels

  • Level 1: ±10% precision (visual inspection)
  • Level 2: ±5% precision (manual measurement with tape)
  • Level 3: ±1% precision (3D scanning or motion capture-assisted placement)

3. Unified Placement Scheme

  • Normalized coordinates (0-100%) within local body segment systems
  • Technology-agnostic approach accommodating various sensing modalities
  • Compatible with existing standards like BIDS and HED
Key Features and Benefits

Reproducibility: Standardized protocols ensure consistent sensor placement across different operators and laboratories, reducing measurement variability and improving data quality.

Scalability: Normalized coordinate systems automatically adapt to different body sizes and proportions, making the framework applicable across diverse populations.

Interoperability: Designed for compatibility with existing data-sharing standards, enhancing the FAIRness (Findability, Accessibility, Interoperability, and Reusability) of collected data.

Flexibility: Accommodates different precision requirements while maintaining consistency, making it valuable for applications ranging from clinical research to consumer health monitoring.

Comprehensive Coverage: Includes detailed specifications for 15 major body segments, covering the full body from head to feet with systematic landmark definitions.

Implementation and Future Directions

The framework is designed to bridge existing domain-specific standards while providing a common language for sensor placement across applications. We identify several key developments for enhancing practical implementation:

  • Vocabulary Development: Collaboration with standards bodies like BIDS and HED for formal specifications and vocabulary cross-references
  • Validation Studies: Multi-operator studies to quantify inter-operator reliability and refine precision specifications
  • Software Tools: Development of coordinate calculation and placement visualization tools
  • Standard Mappings: Explicit mappings between our framework and existing standards like SENIAM
Interactive Framework Website

Explore our comprehensive framework at human-sensor-placement.github.io , which provides:

  • Interactive Landmark Table: Complete anatomical reference with coordinate systems for all body segments
  • Implementation Guidelines: Detailed placement protocols and precision specifications
  • Visual Reference: Anatomical illustrations and coordinate system definitions
  • Community Contributions: Platform for feedback and collaborative improvement
Citation
@ARTICLE{Shirazi2024-sensor-placement,
  title    = "A Standardized Framework for Sensor Placement in Human Motion
              Capture and Wearable Applications",
  author   = "Shirazi, Seyed Yahya and Welzel, Julius and Jeung, Sein and
              Godbersen, Lara",
  journal  = "arXiv preprint",
  pages    = "arXiv:2412.21159",
  month    = "Dec",
  year     =  2024,
  doi      = "10.48550/arXiv.2412.21159",
  language = "en"
}