## Chapter 19 - Alter Course for Carriacou

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```                                                  I made my way into the cockpit and sat beside Mum as she steered the Lord Sheffield around the western corner of the island, past Fort Bay and out to sea. The sails were still furled where we'd left them and we were making way under diesel.
Now that we had power, things like the GPS would be working, so I walked over and turned it on. I'm not completely sure how these things work, but Dad had told me that, aside from what he calls 'the bells and whistles,' what they really do is measure the radio wave time delay, which can be converted to distance, between the boat and a whole bunch of satellites that are whizzing around the earth. A computer inside the GPS then makes triangles out of two satellites and the boat and because the satellites know where they are, using trigonometry, the GPS figures out where the boat is. It does this with lots of satellites, just to make sure and it does it over and over again. Trigonometry is the math of triangles. Mum taught me a little about this in home school.
I knew Mum wouldn't have a clue how to operate the GPS and I wasn't so sure about Sandra or Big Man Jones, so I went to fetch Matthew. Between the two of us, we should be able to figure it out. We were used to electronic devices and Matthew is really good at figuring stuff out.
I now knew from experience, that when you set out on a voyage, the first thing you have to do is plot your course. Mum hadn't even got the charts out yet, so clearly, I was going to have to take charge. I knew we weren't in any danger because we'd sailed this course before and the water was really, really deep. Saba and the nearby islands were created by volcanoes and rise straight out of the depths.
As the GPS fired up, it first sat there with the words "Acquiring Satellites" on the screen. After a minute or two it blinked and another screen came up with a series of numbers. The big numbers in the middle looked like LAT 170 36' 47.26"N – LONG 630 15' 12.36"W. I went inside and got the chart that we'd used to sail to Saba and I found 170 36' 47.26" on the left side of the chart and 630 15' 12.36" on the bottom of the chart. I drew lines across and up from the sides of the chart and they intersected at a point just off Fort Bay. "These numbers," I said to Matthew, "must be latitude and longitude." I think Matthew was impressed.
Now it was his turn. He touched the button labeled "Chart" and the screen changed to a small map with an outline of Saba and Statia and a small, ship-shaped, icon blinking near Saba. The ship-shaped, blinking, icon must be the Lord Sheffield, I thought. Matthew said, "This is easy, it's just like a video game." There was an up/down, left/right toggle button that Matthew now turned his attention to. It moved a computer style cursor around on the screen. He touched the "Waypoint" button on the screen and it put a dot on the screen and asked you to label it. He typed in "test waypoint."
I was figuring out how this worked almost as fast as he was, so looking over his shoulder, I said, "try the 'GOTO' button." Matthew pressed the 'GOTO" button and the GPS asked Matthew to select which waypoint we wanted to "go to" and he selected "test waypoint." Numbers appeared on the screen labeled TTG and DTW and Course Magnetic, among others.
"OK," Matthew said, "I completely get it. These numbers here," he pointed at a small box in the corner of the screen, "have to do with the boat. Things like how fast we're going and which way we're pointed. And these numbers here," he pointed at another box, "are where we are, compared to the waypoint we've chosen. Things like time to go and distance to go before we get there."
"OK," I said, "Now all we have to do is find Guyana on this little map, make a waypoint and point the boat at it. Of course we'd better make sure there aren't any islands in the way."
There was a button labeled "scale" with + and – symbols on it. When I pressed the +, Saba got smaller and more islands appeared. I kept pressing it until eventually we could see Venezuela on the bottom of the screen and below that, British Guyana. I made a waypoint just off of Georgetown and told the GPS to 'GOTO' this waypoint. The GPS drew a line from the Lord Sheffield all the way to Georgetown. I could see that it went very close to St Vincent, but other than that, it was clear sailing all the way. I looked at the waypoint box on the screen and read off the heading to my Georgetown waypoint. "Mum, steer 1900 magnetic. Georgetown is 708 nautical miles away and the time to go is 118 hours or 5 days at our current speed."
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