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Mapping the ASFs of the Northwest European Loran-C System

机译：映射西北欧洲Loran-C系统的ASF

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Loran-C receivers measure time delay differences in the signals they receive, computerndifferences of distance, and hence determine the user's position. The conversion from time torndistance requires knowledge of the signals' velocities, which differ from seawater values whenrnpropagating over land. Precise positioning requires the delays of land paths to be accuratelyrnmapped, a procedure traditionally entailing expensive and time-consuming marine surveys. Thernresulting data, in the form of Additional Secondary Factors (ASFs), may be stored in Loranrnreceivers.rnThe authors, working under contract to the Co-ordinating Agency Office of the NorthwestrnEuropean Loran-C System (NELS) are investigating the feasibility of calculating ASFs usingrndatabases of terrain parameters and then adjusting the resulting predicted values using sparsernmeasurements. These techniques, devised in North America a number of years ago, can nowrntake advantage of GPS for precise position measurement and time transfer. In addition, thernpossibility of minimising the degree of specialised surveying by the use of automaticallyoperatingrnreceiving equipment installed on ferries, buoy tenders, and other ships of opportunityrnis being investigated.rnThis paper introduces the concept of Loran-C Additional Secondary Factors, and shows howrnit is possible to map them efficiently. A review and update on the progress of the work isrnpresented. It focuses on recent advances, chiefly the development of powerful sottware forrnmodelling the growth of ASFs over mountainous terrain. This employs an implementation ofrnan algorithm proposed by Monteath [1]. The modelling capability of the algorithm isrndemonstrated by examining propagation along a route that crossed mountains and dep fjords.rnIn addition, the ASFs it predicts are compared with measurements made around the west coastrnof Scotland.
机译：Loran-C接收器测量接收到的信号中的时延差异，距离的计算机差异，从而确定用户的位置。从时间到距离的转换需要了解信号的速度，这与在陆地上传播时的海水值不同。精确的定位要求准确地消除陆地路径的延迟，这是传统上需要昂贵且费时的海洋测量的过程。结果数据可以以其他次级因子（ASF）的形式存储在Loranrnreceivers中。作者与西北欧洲欧洲Loran-C系统（NELS）协调局合作，正在研究计算ASF的可行性。使用地形参数数据库，然后使用稀疏测量来调整所得的预测值。这些技术是几年前在北美发明的，现在可以利用GPS进行精确的位置测量和时间传递。此外，通过使用安装在渡轮，浮标和其他商船上的自动操作的接收设备，有可能使专门测量的程度降至最低。本文介绍了Loran-C附加次要因素的概念，并说明了可能发生的二次谐波以有效地映射它们。提出了对工作进度的审查和更新。它着眼于最近的进展，主要是开发强大的软件，以模拟山区地形上ASF的增长。这采用了Monteath [1]提出的rnan算法的实现。通过检查穿越山脉和峡湾的路线的传播来展示算法的建模能力。此外，将其预测的ASF与在苏格兰西海岸附近进行的测量进行比较。

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