9.7. Where is North: A Compass App (Optional)

This lesson provides an introduction to the Global Positioning System (GPS) as well as how to handle the complexity of many different screen sizes when designing mobile apps. It reinforces the enduring understandings of writing programs to execute algorithms, such as computing the center of a screen's width, as well as demonstrates how the GPS system in the app allows users to interact with their environment. The follow-up lesson is the My Directions Tutorial in Unit 7 which covers how to build an app that uses a Location sensor and Google Maps to get directions from a current location. The Walking Tour app in Unit 3 also reinforces the concept of GPS and identifying locations on a map.


The Student Lesson: Complete the activities for Mobile CSP Lesson 9.7: Where is North? A Compass App.


Learning Activities

Estimated Length: 45 minutes


Formative Assessment: Interactive exercises on the Mobile CSP lesson page


Read more about the App Inventor Location and Orientation sensors.

Directional Bugs: As some of you are noticing, and as others have noticed in the past, there is a bug in the "Where is North" app. The azimuth correction — adding 90 — doesn't work well for other directions besides North. The reason is that the sprite heading changes from 0 to 360 in a clockwise direction, whereas the azimuth changes from 0 to 360 in a counter-clockwise direction. Alan Tranciato (Meriden High School, Meriden CT) has created a nice fix for this — i.e., he wrote a procedure that converts azimuth to heading. (Procedures are covered in Unit 5.)

9.7.1. Teacher PD Reflection

Discuss the following questions with other teachers in your professional development program.

  • How does this lesson help students toward the enduring understanding that people write programs to implement algorithms?
    [EU 5.2]
  • How does this lesson help students toward the enduring understanding that computing enhances communication, interaction, and cognition?
    [EU 7.1]
  • How does this lesson help students develop the computational thinking practice of analyzing problems and artifacts?
    [P 4]

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