Chapter 6: Field check (text only)

Julie:
Our first SAR image was very close to the city of Fairbanks, in fact from a place called Delta Junction.

We flew to Fairbanks. From our plane Alaska looked so vast, so quiet, and so beautiful - almost mystical.

Next morning Uncle Roger's friend drove the children to Delta Junction. The children hoped that their treasure box would be there.

Steve:
Oh what is this? This does not look like our treasure box.

The children returned to Fairbanks. They went right away to talk to the scientists at ASF.

Scientist:
What you saw was a corner reflector that we set up on purpose in Delta Junction. We know the precise location of the corner reflector. This information is very helpful.

The corner reflector makes a bright spot on the SAR image which we can clearly see. Now we know our exact location on the image.

You can make your own model of a corner reflector and see how it works.

The second site the children visited turned out to be an old broken truck. The third site was a small bridge. The fourth site was a remote deserted cabin with a metal roof.

Tim:
I am so disappointed. Our hopes of finding the treasure box are shrinking.

Scientist:
You should not be disappointed. Your mission is a tough one. You have done so well. You have taken a scientific and systematic approach to the treasure hunt. I am sure that this approach and hard work will lead to success.

Now you have also learned that checking in the field is a very important part of remote sensing. We can make interpretations from satellite images. Sometimes our interpretations can be wrong. Field checking helps us to confirm our observations.

The children did not give up their search. One day they walked eight kilometers to their target as there were no roads. They spread out in two groups to look for the treasure box.

Tim:
Hurray, Hurray! I found it.

Julie:
This was hard work but so much fun. Now we can donate this gold so that other children can also study and play like us.

Tim:
One day I will become a scientist and make my own satellite.

Steve:
I will visit your satellite in space and study the Earth from space.

Activity: Make your own corner reflector

If you want to make your own cool and shiny corner reflector, you will need paper, some aluminum foil, a pair of scissors, and glue.

Got all that? Ok, here we go:

Print out this graphic.
Cut around the outside edges, including the flap for the glue.
Fold along the dashed lines as shown in the figure.
Put glue on the flap labeled 'glue' and paste it on the back side of panel (triangle) labeled 1 so that the model closes to form a trihedral (a figure having three sides).
For a really shiny looking reflector you need to cover the inside of the model with aluminum foil. You can do this by making a similar trihedral with aluminum foil and glue it gently with the paper, before pasting the flap labeled glue to the back side of the triangular panel 1.
Note for teachers: You may want to shine a laser beam from your laser pointer (available for less than $10 in many stores) onto the shiny aluminum surface inside the model and demonstrate how this beam returns back.

Math activity

To convert kilometers to miles we divide the number of kilometers by approximately 0.6. To convert miles to kilometers we multiply the number of miles by approximately 1.6.

Answer the questions that follow:

Q1: A full marathon race is 42.195 km. How much is it in miles?

Q2: The mean distance between the Earth and the Moon is 384,400 km. Convert this distance to miles.

Q3: The length of the Trans-Alaskan pipeline is 800 miles. What is its length in kilometers?

Q4: The length of Alaska from east to west is 2,400 miles, and from north to south is 1,420 miles. Calculate Alaska's length from east to west and from north to south in kilometers.