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San Francisco Bay: Change Detection and Mapping
Pictures Taken from Space Are Used to See Changes
in the San Francisco Bay Area!


 
 Introduction

The three images below are pictures taken from space of the San Francisco Bay area, California. Can you find San Francisco Bay on a map or globe?


1984 Satellite Picture

1993 Satellite Picture

Change Picture


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What's a Change Picture?

The first picture (or image) was taken in 1984, the second in 1993. The third picture is called a Change Image Map. It was made by using the computer to compare the 1984 and 1993 pictures and mapping the changes that happened around San Francisco between 1984 and 1993!

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What kinds of things can we learn from the change image map?

  • Were there more plants, grass, and trees in 1993 or in 1984?
  • Did the cities grow or shrink?
  • Where did the city grow?
  • Does the Earth around San Francisco look like it has been damaged or healed over the years?
Can you think of any other questions that could be answered by looking at the change image? (Hints: clouds, farm crops, water)
 


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What do all the colors mean in the change map?

The colors help scientists see the changes between 1984 and 1993!

Magenta - The magenta areas had more, bigger, or healthier plants and trees in 1984 than in 1993.

Green - This is the opposite of magenta. Green areas areas had more or bigger plants and trees in 1993 than in 1984. This shows up a lot in farming areas, where the crops are bigger, or the farmer has a different kind of plant growing in his/her field in 1993 than in 1984.

Blue - Blue areas show where the city grew between 1984 and 1993. People built new houses, stores, factories, and other kinds of buildings. If you look closely in some areas, you can see the new building as a blue rectangle!

White - These are areas where the Earth's surface is a lot brighter in 1993 than in 1984. For instance, the clouds in the 1993 satellite image show up white in the change image. Another thing that can cause areas of the change image to be white is ground which was burned in 1984 (so is very dark), but was recovering (growing new plants) by 1993.

Black - This is the opposite of white. For example, areas that look black were burnt in 1993, or were new farmland that were natural areas (like fields and forests) in 1984. When farmers make new farmland, they dig up the dirt and turn it over. Dirt can be dark compared to plants, depending what color you are looking at.



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Show Me More!

Here are somecloseupsof areas that changed a lot between 1984 and 1993. Each image shows an area in 1984, 1993, and the change image map.Zoomall the way in on the images, and pay special attention the the change image -

What changes do you see?
 
 

Zoom in on South Bay Area 
South Bay Area
Zoom in on Carquinez Straight Area 
Carquinez Strait Area
Zoom in on Honker Bay Area 
Honker Bay Area


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