Football analytics: when football meets science

Written on 12 November 2017, 09:51pm

Tagged with: , , ,

I wrote a piece about football analytics in Romanian: when football meets science. It was one of the articles I really enjoyed writing and it took me over 10 evenings to do it.

Here are the top level details:

Football analytics is all about using data about previous events in order to have an indication about the outcome of future events.
It is not new: it started somewhere in the ’50 and one of the first coaches to use it was a Russian trainer called Valeri Lobanovsky, in an era where a computer was taking up rooms.
I found a correlation about the DIKW pyramid and the usage of football data:
– Data – numbers and metadata collected using manual operators, tracking devices or video tools
– Information – when data is put into context. One indicator that recently became mainstream is the ‘expected goal‘ (xG) – a percentage associated with every shot based on previously aggregated data
– Knowledge – when information is combined with previous experience. Example – aggregating information about indicators like xG (xG for, xG against, non-shot xG, xG difference)
– Wisdom – using previous levels to take strategic decision enabling competitive advantage.

The first two levels are for the football fans, media writers and TV pundits.
The last two levels are for the professional football clubs and for the betting companies. This is where the football analytics takes places and these levels can give indication about future events.

A few examples of football analytics:
1. transfers: before any transfer, the targeted player is analysed from a few perspectives: tactical, physical, technical. The modern clubs are using players databases with custom criteria in order to maximize their match rate.
2. injury prevention: by tracking the way a player runs and measuring how long his feet stays on the ground, one can evaluate the player tiredness
3. predicting outcome of future events by calculating and maintaining a club index (ex.
4. penalty shoot-out: statistics showed that the team shooting first has a 20% advantage over the second team. The football governing bodies realized this un-fair advantage and recently changed the order of the shoot-out (now ABBA instead of ABAB)

In the end, football remains a random sport. Using analytics can give indications, and make the clubs better understand some questions, but it cannot (yet) give definite answers. As long as football is played by humans, the human factor will play its part and will keep football random and enjoyable.

The graphics on Fifa 16 are something else

Time dilation

Written on 7 August 2015, 02:47pm

Tagged with: , ,

The passing of time can be altered by 2 factors, gravity and velocity.
Increase in both gravity or velocity will slow down time.
1. Gravity: Everything likes to live where it will age the most slowly, and gravity pulls it there (Kip Thorne – the Science of Interstellar)
2. Velocity: A space traveler approaching the speed of light will age slower than another one staying on the earth (Twin paradox).
What does this mean?

On the ISS, time runs slower because of the high speed

Altitude: about 400km
Orbital speed: 8km/s
Time dilation: 0.01 seconds slower every year
The smaller gravity pull from the Earth accelerates the time, but not enough to compensate for the velocity of 8km/s which slows down time. So in the end, an astronaut spending 6 months on the ISS will be about 0.005 seconds younger.

[On the ISS] Velocity has increased for the astronauts, slowing down their time, whereas gravity has decreased, speeding up time (the astronauts are experiencing less gravity than on Earth). Nevertheless, the ISS astronaut crew ultimately end up with “slower” time because the two opposing effects are not equally strong. The velocity time dilation is making a bigger difference, and slowing down time. The (time-speeding up) effects of low-gravity would not cancel out these (time-slowing down) effects of velocity unless the ISS orbited much farther from Earth.

On the GPS satellites, time runs faster because of the decrease of gravity

Altitude: 20.000km
Orbital speed: 4km/s
Time dilation due to velocity: 7 microseconds per day
Time dilation due to less gravity: 45 microseconds per day

The combination of these two relativistic effects means that the clocks on-board each satellite should tick faster than identical clocks on the ground by about 38 microseconds per day (45-7=38)! This sounds small, but the high-precision required of the GPS system requires nanosecond accuracy, and 38 microseconds is 38,000 nanoseconds. If these effects were not properly taken into account, a navigational fix based on the GPS constellation would be false after only 2 minutes.
The engineers who designed the GPS system included these relativistic effects when they designed and deployed the system.
GPS and relativity
[Contrary to popular belief, GPS satellites are not in geosynchronous or geostationary orbits). The satellite orbits are distributed so that at least 4 satellites are always visible from any point on the Earth at any given instant (with up to 12 visible at one time)]

Inspired by: The Science of ‘Interstellar’ Explained (Infographic)