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Grapefruit Geography 101 – A Homeschooling Guest Blog Post

Julianna Trefethen

She’s just 14 years old!

Hi there all you Homeschoolers.  We are the five Trefethens.  We cruise aboard the OMARSEA , our 50 foot sailing boat now bound for New Zealand. On board our crew consists of my Mom and Dad, my brothers Ben and Steve, and me Julianna.  I am fourteen years old.  I love living on a boat and traveling with my family.  On board my Dad is the teacher.  He is also the sailor and takes care of the boat.  He is teaching my brothers and I all about how to raise the sails, steer the helm, navigate with electronics like GPS and also how to use the stars to find out where we are.

We sometimes start the day with an informal discussion.  It can lead us almost anywhere and our Dad likes to use this time to get us to “think outside the box”.  He will ask some questions like “how far is it to New Zealand?” or “How do we sail to Tahiti?”  This can be a little hard on the brain first thing in the morning but it always leads us to a lively project.

Today we were looking at how to determine where we are should our electronic GPS fail.  My Dad believes in Low Tech.  That’s why we used a grapefruit for a globe.  My Dad drew lines of Longitude to explain how it works. It’s awesome, and when we were done we ate the world.

Offshore he keeps paper charts (sailors’ maps) on the counter and we mark down how far we are North or South of the equator (Latitude).  Then we mark how far East or West of Greenwich England we are (Longitude).  He says it starts in England because the British invented Longitude and they decided where to put the prime meridian.  I am from Portland Oregon so if it had been me who discovered Longitude I would have made Portland the starting place. Anyway, we put little x’s on the chart every hour to show where we are.  That way if our GPS dies we can go back to using the old fashion way – the sextant.  It’s a plastic gadget that measures how high the sun or a star is off the horizon.  That’s the easy part though.  Then you have to use your Geometry skills to convert the number of degrees from the sextant to your Latitude and Longitude or Lat/Lon for those sailors out there.  In our class we have paper worksheets to keep track of all the math so it’s not too bad.

What I learned is that the old ways still work even  though they are a little boring. You can use a sextant, a set of tables called sight reduction tables, a stop watch, a pencil and a calculator to find out pretty much exactly where you are on the earth.  It’s pretty neat when you stop and think about it.  I really like math when I get to do something outside of the books.  It makes it fun and I remember more of it when we are done.

You can follow our adventures at www.omarsea.com.  Fairwinds to you.

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