Two Lines to a Point

In the picture

1. 1Lighthouse on the headland.
2. 2Buoy on the water.
3. 3Pencil lines crossing on the chart.
4. 4Protractor on the chart.

Examples

• Using two street signs to find where you are on a paper map.
• A map app showing your location where two directions meet.

Quiz: Two Lines to a Point (Age 13)

1. 1

   When locating a boat by measuring the angle to two landmarks, what do you do on a chart?

   • Draw a line for each measured direction; the boat is where the two lines cross.
   • Draw a circle around each landmark; the boat is where the two circles cross.
   • Measure the distance to one landmark and mark that distance along the coast.
2. 2

   What does the crossing point of the two direction lines show?

   • The boat’s position on the chart.
   • The exact distance between the two landmarks.
   • The direction the boat is facing.
3. 3

   Why are two landmarks used instead of only one?

   • One line only shows you are somewhere along it; two lines cross at one position.
   • One landmark gives your distance from it, but not your direction, so a second landmark is needed for direction.
   • One landmark gives a line, but you need two landmarks to know which way the boat is moving.

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.