millennia humans have located their position on
the Earth with the help of the sun. From the ancient
Egyptians to the armies of the 20th century, the
sun and the stars have provided beacons of reckoning
to sailors, explorers, wanderers, and most everyone
else. Nowadays, of course, we have the global positioning
system (GPS) satellites which can pinpoint our position
on the planet with an accuracy of better than 15
feet. However, it is fun to understand just how
simple it is to find your location using simple
materials you can find in your classroom and a little
is the idea of the Solar Locator Project.
the week before and the week after Winter Solstice
(December 21st), you are invited to make observations
of the altitude in the sky that the Sun reaches
at local noon using our patented Solar Locator.
When all of the measurements are made, you can then
send the data to our central coordinator (see below)
and it will be displayed on this web site so that
it can be shared by all of the groups, regardless
of their locations on Earth.
addition, each contributor will be able to take
the measurements made by the other groups and, from
that data, try to determine where on Earth they
are. Near the end of January, we will post a map
here of the location of everyone who participates.
make the measurements for this activity, you will
need the following:
sheet and instructions, or some other means of
measuring Sun altitude
of the time zone you are in and how to calculate
GMT from your local time
the Solar Locator
Print or copy the solar locator (You will need Adobe
Acrobat to view it - it's free!).
Set up the sheet in front of you on a flat surface
with the printing upright.
Fold the bottom edge up so that it falls right on
the two small lines labeled "Line A" Crease
the fold. The crease should fall on the horizontal
Unfold the paper and lay it flat as before.
Fold the left bottom corner of the paper up so that
it covers the label "Corner B" and the
corner falls on the small cross. Crease the fold.
The crease should fall on the diagonal das ed line.
Fold the right bottom corner up so it covers the
label "Corner C" similar to the previous
step. Crease the fold. The crease should fall on
the remaining dashed line. This part is like the
first step in making a paper airplane.
With the two diagonal folds still in place, fold
up the bottom of the paper along the fold you made
in step 3 so the point falls on the heavy line in
the center of the paper. Unfold the bottom half
way so that the tip points away from the table.
Slide the two edges of the folds out so that they
fall on the diagonal rectangles and tape each side
down with a small piece of tape.
Solar Locator can tell you the elevation of the
Sun anytime. Just place the paper on a flat horizontal
surface and turn it so the shadow of the peak falls
on the heavy center line. Read off the elevation
by interpolating between the marked angles. To use
the locator to find your position:
Mount the locator on a firm, level surface that
is outside and in view of the sun 2) align the
paper so that the top faces north.
Mark the position of the tip of the shadow several
times between 11:00 am and 1:00 pm and write down
the time you made the measurement. For better
accuracy, take measurements every 10 minutes or
so. You can write right on the solar locator.
After all your data points have been taken, draw
a smooth line through the points. This line should
make a "U" shape (one part of the U is due to
the sun still rising, the other part of the U
is made as the sun begins to set).
goal is to figure out at what time the sun was highest
in the sky as well as how high it got. Let's tackle
the second part first. The sun was highest in the
sky at lowest point of the shadow path you drew
out at the end of your observations (the bottom
part of the U). Read the angle off of the solar
locator where this occurs and write it down. You
might need to interpolate between two lines to get
the most accurate answer.
let's figure out at what time this happened. Look
at the times of the points nearest to where you
decided the sun was highest in the sky. Interpolate
between these times to approximate the actual time
of day that the sun was highest. Now convert that
time to Greenwich Mean Time (GMT) using the directions
on the Solar Locator sheet. Write this number down.
Your Longitude and Latitude
From the GMT of Maximum Sun Altitude, calculate:
Longitude = (GMT-12 hours) * 360 / 24 You must
first convert GMT to decimal form to use this
equation. To do this, divide the minutes of time
by 60 and add this result to the hours. For example,
a GMT of 9:37 = 9 + 37/60 = 9.62 in decimal form.
If the answer you get is a negative number, then
the longitude is east of Greenwich. If the answer
is positive, then the longitude is west of Greenwich.
the Maximum Sun Altitude (Sun altitude at local
noon) measured near solstice for each group, calculate:
latitude = 90- your measured altitude - 23.5 (for
measurements made near Dec. 21st.)
To submit your answer, send an email to Grant
Wilson and include the following information:
the city you made your measurements in (so I can
double check your answer!)
your measured time of highest sun altitude
your measured highest sun altitude
the date of the day you made your measurements
6) your estimated longitude and latitude
Luck and check back often for updates and newly
send questions and comments to me at email@example.com.
Stephan Meyer firstname.lastname@example.org
Jennifer Leimberer email@example.com
Gwynne Crowder firstname.lastname@example.org
Ben Burress BBurress@ChabotSpace.org
Daviya Saleme email@example.com
Etta Heber firstname.lastname@example.org
Chris Martin email@example.com
Grant Wilson firstname.lastname@example.org
Randy Landsberg email@example.com