# Creating and Interpreting Images

### Mini Lesson

Images taken from a satellite are often used to display Earth's features. For example, the Landsat image here shows Alaska’s Columbia Glacier. It is one of the most rapidly changing glaciers in the world.

This false-color image, captured by the Thematic Mapper (TM) instrument on Landsat 5, shows the glacier and the surrounding landscape in 2011. Band combinations and shades in this Landsat image were selected to highlight Alaskan landscape.  By obtaining images of the same place using different filters on the sensor, scientists can identify the specific 'colors' of hundreds of different surface features. Let's see how this works!

Snow and ice appear bright greenish-blue color, vegetation is green, clouds are white or light orange, and the open ocean is dark blue. Exposed bedrock is brown, while rocky debris on the glacier’s surface is gray.

Now, let's apply this process to an unknown area!

Suppose that you are an astronomer and you have the first image of a planet orbiting another star. The satellite image of the planet's surface is shown in pixels a 8 (rows) x 9 (columns) grid. Images were obtained in three different color filters: Red, Green and Blue, so that surface features can be classified as water, land, snow or vegetation.

The pixel data sequences for the three tables used to make the "satellite" image are shown below:

1. Create three array (grid) tables (8 columns x 9 rows) using the data provided. See the incomplete examples below on how to create these tables.  NOTE: These instructions are provided in the Google Slide linked in this mini lesson.

2. Use the array tables you created in Step 1 to form a combined array table of coordinates.  Input the numbers from the same relative position in each table to find the coordinates for the sequenced positions. See the example below for the first set of coordinates.   Note: the colors of the data values in the example below are for visual aid only. Students do not need to color their combined coordinates.
3. Use the combined array table from Step 2 and the key below to determine the color of each pixel in the provided grid.
4. Using the key, drag and drop the color cubes from the bottom of the grid to the corresponding pixels as pictured below.
5. Assuming that the planet is perfectly round, draw and color an image of the planet as it might actually appear using the above surface composition information as a clue.

Sources: Inspired by NASA Space Math.

### Teacher Note

Information from satellites if often used to display information about objects. This information can include how things appear, as well as their contents. Explore how pixel data sequences can be used to create an image and interpret it.

There are slides in the Google Slides with array tables already filled out so that this lesson can be adapted for different skill levels. Feel free to take those out if your students are able to put together the tables themselves!