Feb 04 2011
I’ve blogged in the past about maritime Android apps I find useful on my HTC EVO. I can definitely see a future where a marine-version of an Android Honeycomb tablet is fixed to the binnacle of my sloop and offers me a multi-function nav device for GPS enabled chart plotting and a wealth of navigation data from tide tables to an anchor-drag alert. A new app will definitely be on that device.
Vernon Grabel, who founded Cape.com (my ISP) and is a personal baseball/sailing friend, has released a free app into the Android Marketplace called Currents. The premise is drop-dead simple but very convenient as it acknowledges that for most sailors the most important tidal information is not necessarily the time of high and low tide at a specific point, but the velocity and direction of the current caused by the ebb and flood of the tide. A boat’s track from point A to point B is affected by “set” — the lateral movement of the hull due to leeward drift (which is why sailboats have keels or centerboards) and general current direction. which can accelerate speed if coming from astern, slow down if coming head on, or push the boat downwind or upwind. Currents in constricted areas, such as canals, guts, and harbor entrances, can mean the difference between successfully transiting an area or meeting with disaster.
For more than a century, Cape Cod mariners have relied on the familiar yellow covered annual edition of the Eldridge Tide and Pilot Book to determine the current’s velocity and direction for any given point and time. The process of calculating current based on the time of the tide in the major observation points listed by Eldridge and then off-setting that time for the specific spot being transited (e.g. if one is entering Cotuit Bay, one needs to find the time of the tide in Boston and add one hour and seven seconds for high tide, and subtract 45 minutes for low) … it’s time consuming, a serious pain in the ass under sail, and a distraction as one pops below for the book, brings it up to the cockpit, and starts flipping pages back and forth.
Grabel nails the problem with Currents for not only New England but most of the coastal United States. By using the public data published by the National Oceanographic and Atmospheric Administration (NOAA), mashing into Google Maps, and overlaying arrows of varying thickness and length and direction, Currents gives a perfect, zoomable, and accurate current and tide reading for the hundreds of coastal stations tracked by NOAA.
So, this may be the year I save $14,00 on yet another copy of Eldridge and rely on my phone for yet another essential piece of navigational information. Currents is listed in the Google Marketplace under “currents” or “yoyana” or you can scan this: