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Using a Shadowplot to find the North-South line in the Northern hemisphere

After one day of shadow measurements you are ready to draw the
North-South line. (If you have not yet made your shadow plot, click here to learn how to do so.)
On your completed shadow plot draw a smooth curve through all of the
marks that you have made, without moving the paper. The more often you
have taken your measurements, the easier it will be to draw this curve
accurately.
Once you have drawn a smooth curve through the markings, you want to find
the shortest distance between the dowel base and this curve. To do this
place a meter stick so that one end is at the dowel base and the curve
crosses the meter stick at some other point. Pivot
the meter stick about the end at the dowel base until the find the
location on the curve that is the shortest distance from the dowel base.

Draw a line from the dowel base to this point as in the image below.

This line you have just drawn is called a North-South line. It is the
line along which the Sun will cast a shadow at local noon. (Your local
noon may not be exactly when the clock says noon depending on where you
are in your timezone.)
This North-South line points exactly North and South. A line
drawn perpendicular to this line will point East and West. You
will need to know the exact direction of North to use your horizontal
sundial.

Now that we know the direction of north, we need to know our
latitude and then we are ready to make the sundials.

Shadowplot
sundials
Latitude