Assessing the magnitude of fuel consumption of marine traffic is a challenging task. The consumption can be reduced by the ways the vessels are operated, to achieve both improved cost efficiency and reduced CO2 emissions. Mathematical models for predicting ships' consumption are in a central role in both of these tasks. Nowadays, many ships are equipped with data collection systems, which enable data-based calibration of the consumption models. Typically this calibration procedure is carried out independently for each particular ship, using only data collected from the ship in question. In this paper, we demonstrate a hierarchical Bayesian modeling approach, where we fit a single model over many vessels, with the assumption that the parameters of vessels of same type and similar characteristics (e.g. vessel size) are likely close to each other. The benefits of such an approach are two-fold; 1) we can borrow information about parameters that are not well informed by the vessel-specific data using data from similar ships, and 2) we can use the final hierarchical model to predict the behavior of a vessel from which we don't have any data, based only on its characteristics. In this paper, we discuss the basic concept and present a first simple version of the model. We apply the Stan statistical modeling tool for the model fitting and use real data from 64 cruise ships collected via the widely used commercial Eniram platform. By using Bayesian statistical methods we obtain uncertainties for the model predictions, too. The prediction accuracy of the model is compared to an existing data-free modeling approach.
翻译:评估海上交通燃料消耗量的规模是一项艰巨的任务。通过船舶的运作方式,可以降低消耗量,提高成本效率和减少二氧化碳排放量。预测船舶消耗量的数学模型在这两项任务中都起着中心作用。如今,许多船舶都配备了数据收集系统,能够对消费模型进行基于数据的校准。通常,这种校准程序是针对每艘特定船舶独立进行的,只使用从有关船舶收集的数据。在本文件中,我们展示了一种无等级的贝叶西亚模式,我们把一个单一模型放在许多船舶上,假设同一类型和类似特性的船舶参数(例如船舶大小)可能彼此接近。这种方法的好处是双重的;1 我们可以借用关于使用类似船舶的数据来获得船舶特定数据不甚佳的参数的信息。2 我们可以使用最后等级模式来预测我们没有任何数据的船只的行为,我们仅根据这些模型的特性来使用。在本文中,我们讨论同一类型和类似特性的船舶的参数参数(例如船舶大小)的参数可能彼此接近。这种方法的好处是双重的;1,我们可以借用使用从船舶收集的统计模型中获取的简单数据来进行统计的模型。我们从数据库中获取的模型。我们用一个数据库的模型来进行比较。