Line following with camera in Drone Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to capture an image from the drone's camera.

Drone Programming

image = drone.camera.[1]()

Drag options to blanks, or click blank then click option'

Astart

Bcapture

Cmove

Dfly

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'fly' or 'move' which are for drone movement, not camera capture.

Using 'start' which might start the camera but doesn't capture an image.

The capture() method takes a photo from the drone's camera.

2fill in blank

medium

Complete the code to convert the captured image to grayscale.

Drone Programming

gray_image = drone.camera.[1](image)

Drag options to blanks, or click blank then click option'

Agrayscale

Bblur

Ccolorize

Dresize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'colorize' which adds color instead of removing it.

Using 'blur' which softens the image but doesn't convert to grayscale.

The grayscale() method converts the image to shades of gray, which helps in line detection.

3fill in blank

hard

Fix the error in the code to detect edges in the grayscale image.

Drone Programming

edges = drone.camera.[1](gray_image)

Drag options to blanks, or click blank then click option'

Adetect_edges

Bcapture

Cblur

Dresize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'blur' which smooths the image but doesn't detect edges.

Using 'resize' which changes image size but not edges.

The detect_edges() method finds the edges in the grayscale image, which is essential for line following.

4fill in blank

hard

Fill both blanks to create a dictionary of line positions and their lengths from detected edges.

Drone Programming

line_data = {pos: [1] for pos in edges if edges[pos] [2] 0}

Drag options to blanks, or click blank then click option'

Aedges[pos]

B==

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' which only includes edges exactly zero length.

Using '<' which includes edges less than zero, which is invalid.

The dictionary comprehension uses edges[pos] as the value and filters positions where edge length is greater than zero.

5fill in blank

hard

Fill all three blanks to control the drone's movement based on line position and length.

Drone Programming

if line_data.get([1]) [2] [3]:
    drone.move_forward()

Drag options to blanks, or click blank then click option'

A'center'

B>

C10

D'left'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'left' instead of 'center' to check line position.

Using '<' instead of '>' which reverses the condition.

The code checks if the line at the center position has length greater than 10, then moves the drone forward.

Practice

1.

What is the main purpose of using a camera in a drone for line following?

easy

A. To detect the position of the line on the ground

B. To measure the drone's altitude

C. To record videos for entertainment

D. To communicate with other drones

Solution

1. Step 1: Understand the role of the camera

   The camera is used to see the environment below the drone, especially the line it needs to follow.

2. Step 2: Identify the main task for line following

   The drone must detect where the line is to adjust its path and stay on it.

3. Final Answer:

   To detect the position of the line on the ground -> Option A

4. Quick Check:

   Camera detects line position = B [OK]

Hint: Camera's job is to see the line, not altitude or communication [OK]

Common Mistakes:

• Confusing camera use with altitude measurement
• Thinking camera is for video recording only
• Assuming camera is for drone communication

2.

Which of the following is the correct way to start capturing images from the drone's camera in Python?

camera = DroneCamera()
# What next?

easy

A. camera.begin()

B. camera.start_capture()

C. start.camera()

D. camera.capture_start()

Solution

1. Step 1: Check common method names for starting capture

   Usually, methods to start camera capture are named with 'start' and 'capture' in order.

2. Step 2: Match method names with options

   camera.start_capture() uses 'start_capture()', which is a common and clear method name.

3. Final Answer:

   camera.start_capture() -> Option B

4. Quick Check:

   Start capture method = start_capture() [OK]

Hint: Look for method names with 'start' and 'capture' in order [OK]

Common Mistakes:

• Mixing method name order like capture_start()
• Using invalid syntax like start.camera()
• Guessing method names without checking conventions

3.

What will be the output of this code snippet that processes a camera frame to find the line position?

frame = camera.get_frame()
line_pos = detect_line_position(frame)
if line_pos < 0.4:
    print("Turn Left")
elif line_pos > 0.6:
    print("Turn Right")
else:
    print("Go Straight")

Assuming detect_line_position(frame) returns 0.3.

medium

A. Turn Left

B. Turn Right

C. Go Straight

D. No output

Solution

1. Step 1: Understand the value of line_pos

   The function returns 0.3, which is less than 0.4.

2. Step 2: Check the conditions in the if-elif-else

   Since 0.3 < 0.4, the first condition is true, so it prints "Turn Left".

3. Final Answer:

   Turn Left -> Option A

4. Quick Check:

   line_pos = 0.3 < 0.4 means Turn Left [OK]

Hint: Compare line_pos with 0.4 and 0.6 to decide direction [OK]

Common Mistakes:

• Confusing less than and greater than signs
• Ignoring the order of if-elif-else
• Assuming else runs when first condition is true

4.

Identify the error in this code snippet for line following and select the fix:

frame = camera.get_frame()
line_pos = detect_line_position(frame)
if line_pos < 0.5
    drone.turn_left()
else:
    drone.turn_right()

medium

A. Replace 'else:' with 'elif line_pos > 0.5:'

B. Change 'turn_left()' to 'turn_left'

C. Add a colon ':' after the if condition

D. Remove the else block entirely

Solution

1. Step 1: Check syntax of if statement

   The if statement is missing a colon ':' at the end, which is required in Python.

2. Step 2: Verify other parts

   turn_left() is a method call and correct, else: is valid syntax, so no changes needed there.

3. Final Answer:

   Add a colon ':' after the if condition -> Option C

4. Quick Check:

   Missing ':' after if condition causes syntax error [OK]

Hint: Always put ':' after if conditions in Python [OK]

Common Mistakes:

• Forgetting colon after if statement
• Confusing method call syntax with attribute
• Changing else to elif unnecessarily

5.

You want the drone to follow a black line on a white floor using the camera. The camera returns a grayscale image where the line pixels are darker (values near 0) and the floor is lighter (values near 255). Which approach best helps the drone decide how to move?

1. Calculate the average pixel value of the whole image.
2. Find the horizontal position of the darkest pixels (line).
3. Use the position to adjust drone's left or right movement.
4. Repeat continuously while flying.

hard

A. Use only the brightest pixels to follow the line

B. Use the average pixel value only to decide movement

C. Ignore pixel values and move randomly

D. Find darkest pixels' horizontal position and adjust movement accordingly

Solution

1. Step 1: Understand the image data

   The line is darker pixels (near 0), so finding their horizontal position shows where the line is.

2. Step 2: Use position to control drone movement

   Adjusting left or right movement based on line position keeps the drone following the line accurately.

3. Final Answer:

   Find darkest pixels' horizontal position and adjust movement accordingly -> Option D

4. Quick Check:

   Line position guides movement, not average or brightest pixels [OK]

Hint: Track darkest pixels' position to steer drone [OK]

Common Mistakes:

• Using average pixel value which loses position info
• Ignoring pixel brightness and moving randomly
• Following brightest pixels instead of darkest