How did sailors navigate using their portolan maps? making quadrant

Thanks to Prince Henry the Navigator in the mid-1400s there was an explosion of navigating tools.  Suddenly sailors could figure out where they were on the open seas, and did not have to hug the shoreline.  This is a huge development.  One of the primary tools used for this was the quadrant, we made one for our history lesson as part of the Age of Exploration Unit, but it’s also a great science lesson.

What is a quadrant?

A quadrant is a small rod with a quarter circle attached to the bottom.  Hanging from the rod is a string with a weight on the end (a plumb line).

Sailors would sight along the rod and would record where the plumb line hung.  They often used a second person to record as the first person lined it up correctly.  This ensured a more accurate measurement, which you can imagine was difficult on a ship moving along the waves.

During the 1400s quadrants were marked with the latitudes.  Sailors would line up the latitude, and keep it lined up, and would arrive at their correct destination.  Later quadrants were marked with degrees (which is how we think of them now).

The quadrant is also part of why sailors used portolan sailing at the time, because they were taking readings off a quadrant, and drew their maps along those lines, so these two tools reinforce each other.

How to make a quadrant

Gather your supplies (Amazon affiliate links, prices are not the best): dowel rod, paper plate (all the prices on Amazon are stupid, get a somewhat thick plate, not the super thin ones), sharpie, glue gun, yarn, nut (or some other item that is small and has a hole you can thread the yarn through)

1.  Cut your paper plate into 4 roughly equal pieces.

2. Since we are basing our quadrant off of the earlier design, we marked spaces for several locations (I opted for fantastical, rather than real world, what’s the point of being the teacher if you can’t have fun?).

3.  Tie your bolt onto the end of your yarn.  I cut a roughly 12-inch piece, but since we only had appetizer-sized plates, the string was ridiculously long for our project.  Lay your string over your dowel rod towards the end.

4. Use your hot glue gun to put the glue along the edge of the dowel rod, catching the yarn (my kids have been using glue guns for years, if your kids are not able to do this, this is an adult step).

5.  Place your paper plate onto the dowel rod.  I mistakenly glued my string on the wrong end, you want the string to be close to the Narnia end on my sample, not the Darkworld end, sigh.

6.  Now have fun with your fun new Quadrant.  If you want detailed explanations of how to use it, check out Claire’s post on how to use a quadrant.

Tomorrow you get to see how sailors ate during this time, and in a couple of more days, you’ll see how currents and water affected sailors.

See the entire series at The Age of Exploration Unit.