Tech Story 3
Tracking behind obstacles: What can a TrackMan radar really see?
Radar waves are invisible to the human eye and it can be hard to imagine how they can capture a wide array of data points with such immaculate precision and repeatability. Even harder to imagine is how the technology can track moving targets hidden behind visually opaque structures, such as walls and other obstacles. For this unique capability, radar technology is often used in surveillance, rescue, and security applications.
Similar to cell phone signals, radar waves can track around obstacles
To visualize why radar waves can look around corners, consider how cell phones use microwaves to both receive and transmit signals from the phone to the cell tower. We often conduct phone calls inside our bricked homes and offices with no line-of-sight to the cell tower. The signal strength behind a brick wall may be weaker compared to a call made outside, but there is nonetheless still plenty of signal to have a call without interruptions. That’s because micro- and radio waves travel seamlessly and effortlessly around obstacles like brick and concrete.
This seamless tracking technology is also found in a TrackMan, and that’s why it’s possible to position it where tracking of the entire ball flight is optimal: behind the ball, pointing towards the target. This also means the radar is situated behind the club-head at the moment of collision with the ball. However – as explained with the cell phone example – the radar technology effortlessly tracks all its key data points due to its capability of measuring around the entire obstacle, ie. the club head. Scientifically speaking, this unique ability is obtained via complex scattering physics where the radar signal undergoes so-called multipath propagation phenomena on and around the club head, which enables a proprietary TrackMan signal-processing algorithm to track the entire club head.
TrackMan’s CTO Fredrik Tuxen refers to this as ‘4D silhouette surface contour’ tracking of the entire club-head. Specifically, this means that TrackMan 4’s ultra-high frequency system not only measures the entire club-head (back, sides, center and front), but also the ball in front of it. This ‘around corners’ scattering mechanism of radar waves is caused by the fact that the wavelength of the TrackMan radar (in the range of 1 inch / 25 mm) is in the same magnitude order as the objects being tracked (club head and ball).
For an optical system with wavelengths 1 million times shorter, the scattering mechanism is much simpler and is pure reflection based, which is why optical systems can not see around corners. Expressed in layman terms, the radio waves sent from the radar’s transmitting antenna, capture data on the entire club head and ball, and then return it to the radar’s receiving antennas. This means data is captured from the back of the club, around its sides, and all the way to the very front of the club face, and even further on to the ball itself. A confirmation that TrackMan tracks data behind obstacles, as seen in figures 1 and 2 below.
By using TrackMan 4’s Dual Radar Technology, the two radar systems currently track 30 data points instantly and effortlessly. Each of the two radar systems has one transmitter and multiple receivers, making it possible to track club and ball in a 3-dimensional space, ensuring no angle is left out.
One system has an ultra-high resolution for capturing data at short ranges, and is therefore perfectly suited for tracking both impact and short range activity, i.e. putts, chips and wedges. The other radar system is set at a lower resolution for longer distances, making it ideal for capturing long range activity, i.e. measuring ball flight and landing.
very true, but note that it still calculates outcome, based on mesurements:;)
Calculations are math which has no assumption. A ‘calculated’ parameter based on measurements is still a measurement.
If calculation of parameters using measurements involves assumptions or models which are not ALWAYS true, the parameter is not ‘directly measured’.
Superb insight!
Pity in the military we’ve never been able to work out how to get a radar to do this ;)
https://www.quora.com/What-is-terrain-masking-how-is-it-achieved-and-what-are-its-advantages-and-disadvantages
p.s. Info on why a mobile phone works inside is totally wrong. It has to do with the frequency band.
Exactly. Radio waves go THROUGH objects, not around them, because of their wavelength. They need to update this article
Radar waves from TrackMan DO see around the clubhead. The physics are a bit complicated, but here we go:
The wavelength of the TrackMan radar is ½-1½ inches – this is in the same order of magnitude as the club head and golf ball. This means that the radar reflection, the so-called scattering mechanism, is in the ‘resonance region’ (see f.ex. https://www.radartutorial.eu/01.basics/Rayleigh-%20versus%20Mie-Scattering.en.html a simplified explanation of this).
In the ‘resonant region’ the reflecting objects generates ‘creeping waves’ that wraps around the object. An electromagnetic field that impact an object, will generate a current on this object, current are ‘closed loops’ which means the current will also run on parts of the object that is not facing the incident electromagnetic wave. The current will then generate a new electromagnetic field (the reflected signal) which will consequently also be radiated from parts of the object that is not facing the incident electromagnetic wave.
However, no matter the physical explanation the raw data from TrackMan clearly shows that we can see ‘around’ the club head. F.ex. it is clear in the radar signal from TrackMan exactly when the ball separates from the club face despite the club head occluding the ball completely.
Just spent 5 mins looking at that graph. Top answer at the end. I don’t understand any of it but it stopped everyone else too. :-)
That graph is good though, but how come the velocity of the ball isn’t circa 1.5 times that of the club face? (presumed 1.5 Smash factor) and the speed/velocity of the club head dropping at impact is enlightening.