Radial-distance models for the line-transect method.

Mean sightings angle may frequently be larger than predicted by Hayne's fixed-distance model or by Eberhardt's variable-distance model. The modified and generalized Hayne's models are also investigated. An alternative approach, based on hazard-rate analysis, is suggested. A nonparametric right-angle-distance model, however, will generally result in more reliable estimation than any radial-distance model. -from Authors