Wednesday, March 10, 2010

Tracking the elusive shifting sands of the pass, or Hansel and Gretel go into the woods

A little while back, the angry wrathful sea gods threw a lighting bolt at the Sarasota County fire boat, and wrought severe damage to the electronics, including the Raymarine radar, C-80, and Raystar 125 GPS. Verado electronics, radio's, and many other items were also barbecued well done in the incident. All of the Raymarine's data was lost when it meet the evil half cousin of Ready Kilowatt. The fire boat is a sturdy Boston Whaler on steroids, made by Brunswick's government division, and does not draw a lot of water, making it a good choice for Sarasota's "thin waters".

This bring us to the story of how important "Tracks" on your GPS can be for all boaters. The fire boat had to do a night run recently, to check out a report of flares seen in the Gulf. This was not a pleasant night to be out. The weather was cold, winds were high and the Gulf was unsettled. The boat went made it out of New Pass okay, but the approach back was more difficult, especially at night. They got in safely, but they went over part of the bar with a little more than few feet of water under them. Captain Greg Garrison (left below, Mitch Thorne to the right) decided this would be a good time to do some retraining on the electronics, and especially in using tracks. 

Not to belabor the point, but using, and making "Tracks" with your chartplotter is one of the most valuable things you can learn how to do, and one of the very first things I teach boaters how to do on their nav systems. The passes in our area are poorly marked, rarely maintained, shift constantly, and have eaten many a prop. So having a good safe "Track" through them is very important. The training session on the fire boat this day, was on how to make tracks, save tracks, name tracks, and use tracks.
Since we were using the Raymarine C-80, I will use C-80's approach to this, but Garmin's and Furuno's operations are very similar. The general approach to doing a good track through the a pass, is to pick a nice calm day, with good water visibility, preferably at low tide if possible. Always start on the land side, and do this going out the pass. I also like to use a split screen with sounder on one side, and chart on the other. It can be useful to see the bottom depth trending up or down while you do this. 

Start in safe water, and on the Raymarine, press "Navigation Options", then "Tracks", and then "Start Track". Don't see "Start Track"?, just press "Stop Track", discard the active track, and then press "Start Track". Now slowly go out the pass using the deepest safe water path you can find. Be careful to give markers, and the ilk as wide of a berth as possible, so it is more difficult to hit them on a dark and stormy night. Make the course out as straight, and clean as possible. I like to go out about a quarter mile out into the Gulf to insure I can safely approach the track from any angle coming in with no obstacles.  You then stop the track, save the track, and name the track. I also make a waypoint near the start of the track to "Goto" to locate the track. 

You can see above the waypoint, and the bow of the vessel pointed at the track. Once you have your track nailed down, you have the option to covert it to a route that you autopilot can follow. Remember when I said try to keep the track as straight and clean as possible? When you convert the track to a route, the chartplotter has to take the curvy track you made, and convert it to a bunch of straight line segments that closely fit your track. The more curvaceous your path is, the more waypoints it takes to convert it to a route, so steer small damn your eyes. With Mitch at the helm being ever vigilant, a good track was laid down, and the fire boat has a good path in. Next job kids, is to do the other passes, and save off the info onto a chip, so the angry wrathful sea gods can't get your data again.

Going out to dinner on the boat? Turn "Tracks" on before you leave the dock. If you got to the restaurant without hitting anything, you can follow your track back home in the dark, but remember to check the tides before you leave, at both ends of your trip

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