poniedziałek, 6 lutego 2012

Google Fusion Tables map rendering issue?

Yet another excercise, which tests Google Fusion Tables.

The data set contains--among other things--birth place for 600+ rugby players who last year take part in Rugby World Cup in New Zealand. The raw data is available here and here.

On the following diagram (cf. Figure 1) the players are mapped by column containing birthplace coordinates

Figure 1. World's concentration of top Rugby Union players.

The map do not show which player plays for which country. To show that a straight line is drawn from each player's birthplace to the country's capital, the player plays for (cf. Figure 2).

Figure 2. The origin of top Rugby Union players by federation.

Some lines look strange and the problem is particularly evident around New-Zealand-Samoa-Tonga-Fiji. For example it seems that many Samoan players were born at high ocean (cf. Figure 3).

Figure 3. The origin of top Rugby Union Samoan players.

BTW mapping Samoans one-by-one is OK (try it). The problem is when all rows are mapped together by Visualize→Map function.

Accidentaly around 600 miles to the East of New Zealand lies antipodal meridian ie. a meridian which is diametrically opposite the Greenwich meridian (a pime one). The longitude of points lying on antipodal meridian can be referenced (at least in GoogleMaps) both as -180° or 180° (ie. -36,-180° and -36,+180° refers to the same place). Perhaps it is the cause of observed errors...

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