Why inertial sensors and not just video?
Q: New artificial intelligence based apps for mobile/cellphones are available for assessing movement asymmetry. Why would I bother instrumenting a horse with sensors?
A: A great question, and the answer to this will have to be reviewed constantly over the coming years as continuing progress is neing made in both inertial sensor technology and processing as well as in artificial intelligence for markerless tracking of humans and animals.
For now (January 2023), inertial sensor based systems are (still) the more versatile tools. In particular our EquiGait systems provide the following advantages:
1) more complex movements can be measured:
For example, our standard setup is able to measure withers movement in addition to head and pelvis movement. This allows us to draw direct conclusions about whether a measured movement asymmetry is related to force asymmetries between the forelimbs or between the hind limbs.
As a second example, our 6, 8 or 9-sensor wireless systems or our 4-sensor DOT system measure 6-dimensional movements of the back. This is still very difficult to achieve from a single-camera setup due to possible occlusions (the back not easily visible from in front of the horse or from behind) and since multi-dimensional quantification (more than 2 dimensions) is not without challenges from a single camera view. Attaching a sensor to the horse overcomes these challenges.
2) straight-line and lunge and ridden:
similar to the challenges with quantifying multi-dimensional back movement from a single camera, it is more challenging to analyze video data where the viewing angle (between the camera and the horse) is constantly changing. Think lunge or ridden exercise as an example. For now, inertial sensors, mounted on the horse and hence with the measurement reference system moving with the horse, have advantages for this application.
3) measure the unseen:
Oftentimes, subtle movement deficits maybe felt while you are riding your horse. If you want to measure sublte changes affecting the horse in this situation, including the movement of the back, optical systems, including expensive 3D motion caputre systems based on multiple cameras will struggle to provide measurements of all regions of interest, in particular what is going on with the back of the horse under the saddle.
4) anywhere, anytime:
Data analysis is made on your device (Windows laptop/tablet) and does not require internet access) as some other cloud based artificial intelligence tools may need. Results are available in seconds (wireless systems) or reliably (without internet access!) a couple minutes after the measured exercise (DOT system). Other systems that depend on 'cloud computing' may experience variable delays depending on network availability and speed.
5) trade-off between instrumentation time versus analysis time.
Of course putting sensors on horses takes up a little bit of time. In our experience, the more often you do this the better and faster you get. Putting 3 sensors (our minimum setup) on the horse will take in the order of 2 minutes. Once the sensors are on the horse you can perform as many measurements (within battery-life, 5 to 6 hours) as you want and the analysis will be done in seconds, every time! A great benefit during complex lameness exams! No waiting for data upload or analysis!
6) no ongoing subscription fees.
Our systems do not require signing up to a monthly or case-based subscription system as typically encounterd for cloud-based services. The system is yours (once you have purchased it!).
Q: is there any sense in using both: inertial sensor and video/AI based analysis?
A: Absolutely! Combine more complex analysis enabled by our EquiGait systems with long-term assessment over a period of time through mobilephone-based measurements.
As outlined above, we believe there are still a number of advantages to using our multi-sensor approaches, in particular when it comes to assessing more complex interactions between multiple landmarks (head, withers, pelvis) or more complex 6-dimensional patterns of back movement. However, what is wrong with establishing the 'normal pattern' of head and pelvic movement of your horse? Or how about measuring your horse's movement in conjunction with changes to your training regimen or over a period of rehabilitation?
Our EquiGait systems still proivide you with state-of-the-art insights into more complex patterns and exercises, once the time comes to do so!
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