Last November, I proposed that for this Summer’s world Cup Altitude will be key, the thinner air in Johannesburg will cause the ball to behave significantly differently than at sea level. Less air resistance means faster shots and straighter trajectories. As part of a feature for the New Scientist (p35-37, June 5th 2010) we created a shot simulator to show how the same shot behaves at different altitudes. I also studied matches played by Mexico in the FIFA World Cup preliminary rounds leading to the current Finals, including home games at Mexico City at an altitude of 2,200 m.

Fig 1. Maradona lifts the World Cup in Mexico’s Azteca Stadium in 1986.

The raw data, provided by Prozone, comes from the analysis of synchronised high definition video cameras at each game. Eight World Cup Preliminary matches involving Mexico were analysed (Table 1) and the venues categorized using FIFA’s definitions as near sea-level (0-500m), low altitude (500-2,000m) and moderate altitude (2,000-3,000m). Although the data set is quite small (and one must always be careful about using small numbers to make big conclusions), there are some interesting trends.

Date Home team Score Away team Venue Altitude Definition 19-11-2008 Honduras 1-0 Mexico San Pedro Sula 80 m Near sea-level 28-3-2009 Mexico 2-0 Costa Rica Mexico City 2,200 m Moderate 1-4-2009 Honduras 3-1 Mexico San Pedro Sula 80 m Near sea-level 6-6-2009 El Salvador 2-1 Mexico San Salvador 660 m Low 10-6-2009 Mexico 2-1 Trinidad & Tobago Mexico City 2,200 m Moderate 12-8-2009 Mexico 2-1 United States Mexico City 2,200 m Moderate 9-9-2009 Mexico 1-0 Honduras Mexico City 2,200 m Moderate 25-9-2009 Costa Rica 0-3 Mexico San Jose 1,200 m Low

Table 1. FIFA qualifying matches involving Mexico.

Figure 2 shows that shots from outside the box increase from just less than 5 per game at sea level to over 7 per game at moderate altitude. Conversely, the number of shots from inside the box seems to decrease. This is translated directly into the number of shots on target, with more from outside the box than inside the box. The implication is, therefore, that players playing at altitude might be more inclined to take shots from longer distance to take advantage of the straighter, faster trajectories. Whether this results in more goals is difficult to say as there isn’t really enough data in this data set, so I’ve stopped here.

Figure 2. The effect of altitude on shots from inside and outside the box during 8 FIFA World Cup qualifying games (data courtesy of Prozone).

South Africa

The consequences for the World Cup Finals in South Africa will be interesting to see. Will there be more shots from outside the area in Johannesburg? The ball bends less and flies faster at altitude for a given kick, so shots will tend to be straighter and faster. Will players go for curling shots or straight shots? Will the goalies complain?

One thing that seems quite certain, though, is that adidas has done its utmost to produce the most engineered ball for any World Cup so far (see the video below to see how a ball is made). The ball is constructed from eight 3D panels and thermally bonded together around an internal bladder. Their tests show that the ball should fly relatively straight when it has little or no spin, a ‘wobbly’ ball is something that goalies in particular have complained of in the past. Most importantly, the ball will be consistent so any odd occurrences should be due to the player or environmental factors.

So, after the pomp of the opening ceremony on June 11th has subsided, sit back to enjoy the first game between South Africa v Mexico, two teams who should have significant experience of the effects of altitude on play. Let’s see how the players react and if they really do go for shots from distance.

Note: Steve Haake acts as a consultant for adidas.