Be sure Squeak is installed successfully on your computer. It will take about 30 seconds for the project to load for a fast connection (up to 10 minutes for a slow modem connection). Wait until you see an orange flap at the lower left labeled Navigation. Click the flap to open and close it and access some neat tools. You will need to click Escape Browser so you will have more space. Click Browser Reentry to get back your Browser controls.
In this activity Norbert and Zot are world travelers. Your job will be to locate them with the GPS. Every time you click on Norbert and Zot, they travel to a new location (sometimes up in space!). They will send you their distances from three of the color coded satellites above the earth. You have to enter the distances into the GPS boxes at the left and then locate them by pressing the appropriate trilaterate button for your system of three satellites.
Wait a minute! What is trilaterate? On a flat surface, like a computer screen, if Norbert and Zot are say 124 units from the green satellite, then they are somewhere on a circle of 124 uints with a center at the green satellite, but that's all we know from the green satellite. Draw this on paper as you read these words to get a more clear picture. But we also have the distance from say the blue satellite, so we can draw a second circle. Two circles that cross will have two points where they intersect (They could touch at one point, but that's a special case.) So to locate Norbert and Zot, we need a third circle from the red satellite, which will intersect at only one of the two points most of the time. That's trilateration!
When then circles all intersect at one point and you see where Norbert and Zot are, then you must identify the place. Use an atlas or world map to help you. It's much more fun to play with the activity and you will understand trilateration better. So go ahead and click on the GPS button at the left, but return to this page for the challenges once you are familiar with the activity. For two of the challenges you create Squeak projects of your own by modifying the GPS challenge. When you are done go to the NASA CONNECT web site and submit your versions of the Squeak project and we will post all that work correctly for others to learn from and enjoy.
Need help? Come back to this page to print out the Etoys Quick Start Guide and check these tips. Or even better, do it now.
