Uncle Roger:
I have some SAR images with me. Have a look at these images.
This is a SAR image of a river.
Steve:
That is easy. I could have told you that. Look at all the meanders (bends). Only a river can form such a shape.
Uncle Roger:
Here is an image of a glacier.
Tim:
This is so exciting. Look at all the stripes. I can make out how the ice is flowing.
Uncle Roger:
I also have an image of a city. This looks very different.
Tim:
This is confusing. What are all those bright spots? Are they having fireworks in the city?
Uncle Roger:
In cities you have many roads and buildings. The buildings next to roads can act as corner reflectors. A corner reflector is an object that returns a signal to where it came from using multiple reflections.
The signal sent from the satellite bounces off the road, hits the side of the building, and then returns straight back to the satellite.
This signal that reaches straight back to the satellite is very strong. It produces a bright spot in the image.
Julie:
Oh, now I see. Perhaps, the treasure box will also serve as a corner reflector. Then it will show up as a bright feature on the SAR image. We can use this clue to find it.
Uncle Roger:
You are right. Good luck with your mission.
More information: Alaskan Rivers
Alaska has thousands of rivers. More than 12,000 rivers have been counted, but this number does not include thousands of smaller tributaries (streams that flow into a larger river or lake).
The Yukon River is the longest river in Alaska and is more than 1,980 miles long (source: USGS). The river starts in the Yukon, Canada and flows through Alaska.
The other three important rivers are the Kuskokwim River, the Colville River, and the Copper River.
Rivers in Alaska serve as a source of water, food, and routes of transportation.
More information: Alaskan glaciers
Glaciers are an important part of Alaska's landscape.
Did you know that:
While Alaska makes up approximately 17 percent of the area in the US, it accounts for one-third of the US fresh water supply.
Over three-quarters of Alaska's water are "locked up" in the form of glaciers.
Approximately 5 percent of Alaska (about 29,000 square miles) is covered by glaciers.
Alaska's glaciers are located primarily in the southcentral and southeastern portions of the state.
The famous Columbia Glacier has retreated (become smaller) over a mile in less than a decade.
If all the glaciers in Alaska melt, the sea level will rise by nearly a foot.