Follow by Email

Monday, January 30, 2012

Finding Our Way

Recently, I had dinner at a seafood restaurant. Like most seafood restaurants in New England (indeed, most probably around the world), the decoration had a nautical theme. In this case; light houses. A young girl and her grandmother, at another table, was admiring them, with the girl being partially curious about why light houses were painted so:

It took me some effort to be a "know it all" and explain about the role light houses played in coastal navigation. How at night, their lights were often timed to identify each of them, and alert sailing ships of the reefs and sand bars. How, if you could identify one, you knew approximately where you were, and could figure how far from the coast you were by geometry and taking sightings from both the fore and aft of the ship you were on...
I also had learned a bit about the problems of navigating the open sea from both history lessons about the search for a time keeping piece that would function well aboard a ship (the first wind up clocks with free wheels instead of pendulums), and from reading James Clavell's Shogun, in which the "Pilot's log" of a captured Portuguese navigator figured prominently. Latitude, I knew, was calculated by use of a sextant to measure the angle of elevation of charted stars and planets, listed in a celestial log called an Ephemeris. Knowing the latitude of position, knowing direction of travel (via compass) and knowing time elapsed in travel allowed a navigator to plot the Cartesian coordinates on a Mercator map system of charts. This system of navigation was never very precise, and prone to error (failure to account for deviation of magnetic from true north, failure to account for changes in distance scale along latitudes, etc.) but was reliable enough to function for 3 centuries or so...
Of course, orienteering lessons while in the Boy Scouts taught me about magnetic deviation and map reading, but never taught me much about how to use other methods to determine true north, nor what to do when lost amid a forest, concealing land marks. This inadequacy cost me some when I became separated from a hiking group on the Presidential Range in N.H. without a map. Fortunately, following a stream down hill lead me back to one of the main trails...
I knew about geographic survey maps that gave topographic details, but didn't know how to find them until I had a job with the Yankee Atomic Labs that required my fetching them. They are usually available at sporting goods stores, along with state atlases that contain regional topographic maps.
Somewhere along the way, I became interested in private sailing craft, and the skill sets required for solo voyaging. That's when I began to learn about LORAN Sets that used land based radio broadcast signals to triangulate position for both sea and air craft.
This brings us up to the "now" of GPS, and smart phone guidance, using cell tower signal locations to track relative position. We have Mapquest and Google maps, as well as satellite images, to show us the terrain and give us reasonable directions. I have a hand held GPS unit that cost about $40, a Blackberry that cost me $99, but is now about $50, and has a Verizon navigator app. I can down load maps on line..But, i haven't thrown out my compasses, nor my maps, yet...

No comments:

Post a Comment