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Table 4 Group GPS features extracted per time window and cow

From: Inferring an animal’s environment through biologging: quantifying the environmental influence on animal movement

Dimension Statistic Description
Net distances to other cows Mean  
# cows within 2 m radius  
# cows within 4 m radius  
# cows within 8 m radius  
# cows within 16 m radius  
All mean cow coordinates Group elongation index, φ Variance explained by the first principal component through the mean x and y coordinates of all cows. Value lies by definition between 0.5 (when completely non-elongated, e.g., an exact circle) and 1 (when all coordinates lie on a straight line). Afterwards scaled between 0 and 1, by subtracting 0.5 and multiplying by 2.
Group area proxy πσ2(1 − φ); where σ is the standard deviation of the first principal component values. This measure assumes that the area can be estimated by considering the group as an ellipse. When completely non-elongated the area is πσ2 (where the variance σ2 is a proxy for the extent of the direction of elongation) and when fully elongated the area is 0.
Directions to other cows ρ Length of the mean resultant vector
Periphery index Maximum difference between consecutive directions, minus \( \frac{2\pi }{\# cows-1} \) and divided by 2π