Résumé
The mathematically exact solution for navigating with respect to two non-orthogonal gradient fields requires taking both fields into account conjointly. Such a complex solution may be beyond the brain capability of most animals. Animals may use an approximate, simpler solution by considering each field separately (i.e., the angle between the two gradient directions is ignored). This generates directional biases that may prove useful in determining the nature of the fields actually involved in bicoordinate navigation.