Background for activities: Digitizing a wave Reconstructing a digital wave

Digital Imaging Information may be carried by waves. To transmit or record waves electronically, a copy must be made. An exact copy is called an analog. Computers process numbers, not waves. Waves must be digitized. Analog-to-digital converters sample the analog signal at regular intervals, measure a property, and express it in numerical terms. When numerical measurements are placed in their original order, the pattern can be reconstructed.

When visible information, such as a photograph, is digitized, each sample is called a pixel. The more samples that are taken, the more information will be used to reconstruct the original signal. This is called the resolution. The more pixels, the greater the resolution. Numerical information can be processed in many ways to get the visualization desired, like assigning colors to reveal patterns in the data.

Pixel: Short for “picture element” Each pixel is a digital sample of the image. The more samples you take, the more information you have to work with. More information = greater resolution.

Pixel size determines resolution 82,000 Tiny Pixels 88 Giant Pixels

How much resolution you need depends upon how much detail you need. More resolution means more information: more data to look at, but also more to store. File size: 99.3 kb File size: 4.1 kb

Remote sensing can sense, process, record, and store data. Human beings can interpret data. Image Interpretation Visualization The process of creating meaningful images from data.

Reconstructing a digital image 1.The digital image has rows and columns of numbers, which when assigned values become the picture elements (pixels) of the image. 2. Notice the color palette for this image. Color in the digital image according to the palette. 3. What are you seeing? If you know it’s an island, what does the color blue represent? 4. If you know it’s an elevation map, which color is the highest elevation? The lowest? 5. Does the size of the square (the pixel) affect how much information you get from the image?

The island of Oahu, in Hawaii What kind of terrain does Oahu have? If you could scan another image of Oahu, how could you get more detailed information?

This activity courtesy of Hawai’i Space Grant College, Hawai’i Institute of Geophysics and Planetology, University of Hawai’I, class_acts/dnimages.html

Quickie memory aids: Latitude/Longitude

Latitude and Longitude Activity Divide your classroom into Northern and Southern Hemispheres. The Equator is the aisle that divides them. With your students, assign approximate latitude and longitude values to each row of desks. Kids will know if they sit at 45 degrees north or 45 degrees south, at 60 degrees east or 60 degrees west. You may even have students at the North or South Poles!

The Latitude Dance Stand on the Equator, arms outstretched to your sides. Sway left and right and chant: Latitude lines go left and right, but measure North or South. As you say “North”, stand on tiptoes and reach up, and as you say “South”, bend at the knees. Repeat several times– kids love it (and remember it!)

Background for activities: Find It! Measure This

A "compass rose" is an illustration such as the one on this page, showing the points of the compass. The main directions: north, south, east, west are called the "cardinal points" of the compass. Always look for the compass rose, or perhaps a "north arrow", to see in which direction an image is oriented. North isn’t always at the top, although that is a popular convention.

One convenient and precise way to point to a certain spot on a picture or a map is by the Cartesian Coordinate method. If we want to talk about a feature such as a lake, road or field in a satellite image and we don’t want to mark up the image itself, then we can use two numbers to identify the spot. The first number is always the horizontal distance and the second number is always the vertical distance. Using Coordinates horizontal verticalvertical

In the example here, the star has a horizontal coordinate of 4.4 and a vertical coordinate of 2.8, written as: (4.4, 2.8). Use a straight edge like a ruler or a piece of paper to line up the numbers. Make sure the straight edge is exactly parallel to the edge of the image. This can be done by connecting the same number (4.4 in this example) on both the top and the bottom scale. Do the same for the second number by lining up the same number (2.8 in this example) on both the left and right scales. To see if you can do this, try to find the coordinates of the centre of the circle in the diagram. They are: ( ____, _____ )

General Resources _l1/emspectrum.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know _l1/emspectrum.html ImagesTe.htmlhttp:// ImagesTe.html n_plans.htmlhttp://imagine.gsfc.nasa.gov/docs/teachers/lesso n_plans.html s/interact/electromagneticspectrum.htmlhttp://school.discoveryeducation.com/lessonplan s/interact/electromagneticspectrum.html h/em_spec.htmlhttp://marine.rutgers.edu/mrs/education/class/jos h/em_spec.html JI_DigitalInfo_lesson3_1/default.aspxhttp://www97.intel.com/discover/JourneyInside/T JI_DigitalInfo_lesson3_1/default.aspx me.htmlhttp://science.hq.nasa.gov/kids/imagers/echoho me.html

For Help: AMSTI-GLOBEThe GLOBE Program Judy ReevesLynn VaughanAMSTI-GLOBEResource Specialist Robin NelsonJerry CobbsAMSTI-GLOBE AdministratorTechnology Specialist