Schweder T, Skaug H J, Langaas M, Dimakos X K
Department of Economics, University of Oslo, Norway.
Biometrics. 1999 Sep;55(3):678-87. doi: 10.1111/j.0006-341x.1999.00678.x.
The conventional line transect approach of estimating effective search width from the perpendicular distance distribution is inappropriate in certain types of surveys, e.g., when an unknown fraction of the animals on the track line is detected, the animals can be observed only at discrete points in time, there are errors in positional measurements, and covariate heterogeneity exists in detectability. For such situations a hazard probability framework for independent observer surveys is developed. The likelihood of the data, including observed positions of both initial and subsequent observations of animals, is established under the assumption of no measurement errors. To account for measurement errors and possibly other complexities, this likelihood is modified by a function estimated from extensive simulations. This general method of simulated likelihood is explained and the methodology applied to data from a double-platform survey of minke whales in the northeastern Atlantic in 1995.
传统的通过垂直距离分布来估计有效搜索宽度的线断距方法，在某些类型的调查中并不适用，例如，当检测到航线上未知比例的动物时，动物只能在离散的时间点被观测到，位置测量存在误差，并且可探测性存在协变量异质性。针对此类情况，开发了一种用于独立观测者调查的风险概率框架。在无测量误差的假设下，建立了包括动物初始和后续观测的观测位置在内的数据似然性。为了考虑测量误差以及可能的其他复杂性，通过从大量模拟中估计的函数对该似然性进行修正。解释了这种模拟似然性的一般方法，并将该方法应用于1995年东北大西洋小须鲸双平台调查的数据。
