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Showing posts from December, 2019

Free Barometer App Designed for Mariners

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Not many mariners realize that the most accurate barometer on the boat might be in their pocket... in their cellphones. There are not any native functions in iOS or Android phones that show the pressure reading, so you would not know it is there by just surfing around the functions of your phone.  It is not listed anywhere.  A third party app is needed to test that you have one.  There are many free versions of such apps, which brings up point one. Why do we make another one when there are so many already?

We want to let folks know about this tremendous resource, but then we are asked for an app recommendation, and the problem begins. Until now, the apps have all been too complicated. They want to do more, so they end up doing things like getting your elevation from the GPS, which even with a WAAS satellite connected is not accurate enough for barometer work adaptable to marine navigation.  In these days of remarkable weather services via model forecasts, we want the pressure accurat…

Weems & Plath Expanding Square SAR Course Identifier #113

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A common search pattern used in search and rescue (SAR) operations is called the expanding square pattern, which is just what it says it is. You travel along calculated route legs in a pattern that expands every 3rd leg so you systematically cover the the search area in an expanding pattern, as shown below.




To plan out such a pattern you need to know your (1) initial heading, (2) the distance you want between the squares, (3) your boat speed, and (4) the time you plan to start. 
In one sense, the next logical step is turn to your electronic charting program, put in the way points, select an average speed and start time, and look at the resulting route plan, which will tell you the headings and times to turn onto each leg.  Then print that plan or take a picture of it with your cellphone.  In fact, the route itself will be laid out on the chart plotter and you can just follow it.
Or you could simply start off with the boat's track showing, and create the route from your displayed a…

Race to Alaska (R2AK) Navigation

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A question came up in our online nav course about R2AK navigation. As it turns out we have worked on this route in great detail a couple years ago as we assisted the Team MAD Dog in preparation for their record setting race. I started to answer this longish question in our class discussion forum, but decided it could be of broader interest, so I put these notes here.

All such planning starts with the waypoints. We made this set for the full race that the team then transferred into their two handheld GPS units and also into Navionics "Boat US and Canada" app on two iPhones and one Android phone. This app for about $50 includes all Canadian charts. They are not as good as the official Canadian echarts, but those cost $200 or $300 from EC... although there is a very good set from RosePoint Navigation for $99 the last I Checked, but these may only work on Coastal Explorer.

PS. There are some tricks to getting an external gpx file into a mobile app version of Navionics. On the ot…