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Maritime – some useful snippets
Information of interest in the field of offshore survey is kept here.
VORF has become the reference of choice, particularly in wind farm installations close to shore. It has caused a good deal of fear and confusion and so, in a shocking act of plagiarism, we have produced our VORF for DUMMIES page, where you will find what you really need to know.
It can be daunting to move from tangible, but fragile and labour-intensive serial connections to the more flexible world of UDP connections, especially if networking is seen as an arcane art. But with a little practice it becomes easy. Here’s a fairly straightforward guide. In the spirit of these pages, it’s aimed at planners of on-line survey systems, although the principles apply on any network.
NTP is the most advanced method of synchronising computer clocks, and so is important in systems such as offshore survey spreads, where accurate timing of data is crucial. This page is not an attempt at a tutorial on NTP, but simply a note on getting the basics of time synchronisation working, especially when using GPS systems as reference clocks.
HiPAP analogue transponder frequencies always present a challenge when more than one vessel needs to use transponders in the same area. Here is a page that expands on the information in the Kongsberg manual, suggesting some strategies and tables that can be used to create a channel plan with the minimum of interference. There is a PDF version that is useful for printing out, or download an ODF version or MS Word version if you would like to make your own improvements. (The original documents from 2009 are still on the server, and might turn up a Google search).
Note by the author: I’ve come across clients who had downloaded this document and included it in their own documentation. I’m very flattered by that. I was less flattered by the fact that there was no attribution to Sealand, and our copyright notice was not present. We are more than pleased if you find it useful, which is why we made it public, but please treat it with the proper respect.
A single page table that lays out all of the frequencies, and might be useful alongside the planning document above, is available as a .PDF here.
HAIN (Hydroacoustically Aided Inertial Navigation) from Kongsberg Maritime provides much improved navigation of surface and underwater vehicles when used in conjunction with Kongsberg’s HPR/HiPAP sonar positioning systems and APOS. It was also an essential part of the Hugin AUV project.
We published this note about time synchronisation in the HAIN system way back in 2008. It was not documented anywhere else at the time, but it may only be of historical interest now.