Range finder for terrain following in Drone Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read the distance from the range finder sensor.

Drone Programming

distance = sensor.[1]()

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

Ameasure

Bget_distance

Cread_distance

Dfetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not exist on the sensor object.

Confusing the method with one that sets values instead of reading.

The method read_distance() correctly reads the distance from the range finder sensor.

2fill in blank

medium

Complete the code to check if the drone is too close to the ground.

Drone Programming

if distance [1] safe_height:

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

A<

B>=

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>=' instead of '<' which reverses the logic.

Using '==' which only checks for exact equality.

The condition distance < safe_height checks if the drone is closer than the safe height to the ground.

3fill in blank

hard

Fix the error in the code to update the drone's altitude safely.

Drone Programming

drone.altitude [1] safe_height

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

A==

B-=

C+=

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' which is a comparison, not assignment.

Using '+=' or '-=' which modifies the value instead of setting it.

To set the drone's altitude to the safe height, use the assignment operator '='.

4fill in blank

hard

Fill both blanks to create a dictionary of distances for each sensor if the distance is less than the threshold.

Drone Programming

distances = {sensor_id: [1] for sensor_id, [2] in sensors.items() if [1] < threshold}

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

Adistance

Bdistance_value

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variable names causing errors.

Using the same variable name for both keys and values.

The dictionary comprehension uses distance_value as the value and variable for sensor readings.

5fill in blank

hard

Fill all three blanks to filter sensors and create a dictionary with sensor names in uppercase and distances greater than minimum distance.

Drone Programming

filtered = { [1]: [2] for [3], [2] in sensor_data.items() if [2] > min_distance }

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

Asensor.upper()

Bdistance

Csensor

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing variable names causing confusion.

Not converting sensor names to uppercase.

The dictionary keys are sensor names in uppercase (sensor.upper()), values are distances (distance), and the loop variable for sensor names is sensor.

Practice

1.

What is the main purpose of a range finder in drone terrain following?

easy

A. To measure the distance between the drone and the ground

B. To control the drone's speed horizontally

C. To detect obstacles in the air above the drone

D. To measure the drone's battery level

Solution

1. Step 1: Understand the role of a range finder

   A range finder is a sensor that measures how far the drone is from the ground below it.

2. Step 2: Connect measurement to terrain following

   This distance helps the drone adjust its height to follow the shape of the terrain safely.

3. Final Answer:

   To measure the distance between the drone and the ground -> Option A

4. Quick Check:

   Range finder = distance measurement [OK]

Hint: Range finder always measures distance to ground [OK]

Common Mistakes:

• Confusing range finder with speed sensor
• Thinking it measures battery or air obstacles
• Assuming it controls horizontal movement

2.

Which of the following code snippets correctly reads a range finder sensor value in a drone program?

1. distance = range_finder.read()
2. distance = read.range_finder()
3. distance = rangeFinder.readValue()
4. distance = range_finder.get()

easy

A. 2. distance = read.range_finder()

B. 3. distance = rangeFinder.readValue()

C. 1. distance = range_finder.read()

D. 4. distance = range_finder.get()

Solution

1. Step 1: Identify correct method call syntax

   In drone programming, sensors are often objects with a method called read() to get current values.

2. Step 2: Check each option for correct syntax

   Option 1 uses range_finder.read(), which is standard and correct. Others use incorrect method names or syntax.

3. Final Answer:

   1. distance = range_finder.read() -> Option C

4. Quick Check:

   Sensor read method = read() [OK]

Hint: Sensor reading usually uses .read() method [OK]

Common Mistakes:

• Using wrong method names like get() or readValue()
• Incorrect object.method order
• Confusing variable names with method calls

3.

What will be the output of this code snippet controlling drone height?

distance = 5
if distance < 3:
    action = "ascend"
elif distance > 7:
    action = "descend"
else:
    action = "hold"
print(action)

medium

A. "ascend"

B. "hold"

C. "descend"

D. Error

Solution

1. Step 1: Evaluate the distance condition

   The distance is 5. Check if 5 < 3 (false), then if 5 > 7 (false).

2. Step 2: Determine the else branch

   Since both conditions are false, the else branch runs, setting action to "hold".

3. Final Answer:

   "hold" -> Option B

4. Quick Check:

   Distance 5 triggers else = hold [OK]

Hint: Check conditions in order, else runs if none match [OK]

Common Mistakes:

• Choosing ascend or descend incorrectly
• Confusing comparison operators
• Assuming error due to syntax

4.

Find the error in this drone height control code:

distance = range_finder.read()
if distance < 2
    action = "ascend"
else:
    action = "descend"
print(action)

medium

A. range_finder.read() is invalid

B. Wrong comparison operator

C. Incorrect indentation of else

D. Missing colon after if condition

Solution

1. Step 1: Check syntax of if statement

   The if statement is missing a colon (:) at the end of the condition line, which is required in Python-like syntax.

2. Step 2: Verify other parts

   Comparison operator and indentation are correct. The method call is valid assuming range_finder object exists.

3. Final Answer:

   Missing colon after if condition -> Option D

4. Quick Check:

   if statement needs colon : [OK]

Hint: Always put colon after if condition [OK]

Common Mistakes:

• Forgetting colon after if
• Misaligning else indentation
• Changing comparison operators unnecessarily

5.

You want the drone to maintain a height of 4 meters above ground using the range finder. Which code snippet correctly adjusts the drone's vertical speed based on the measured distance?

distance = range_finder.read()
if distance < 4:
    vertical_speed = 1  # ascend
elif distance > 4:
    vertical_speed = -1 # descend
else:
    vertical_speed = 0  # hold steady
print(vertical_speed)

hard

A. This code correctly sets vertical_speed to keep 4m height

B. The conditions should use <= and >= instead of < and >

C. vertical_speed values should be reversed for ascend and descend

D. The else block is unnecessary and should be removed

Solution

1. Step 1: Understand the desired behavior

   The drone should ascend if below 4m, descend if above 4m, and hold if exactly 4m.

2. Step 2: Check code logic

   If distance < 4, vertical_speed = 1 (ascend) is correct. If distance > 4, vertical_speed = -1 (descend) is correct. Else holds steady at 0.

3. Final Answer:

   This code correctly sets vertical_speed to keep 4m height -> Option A

4. Quick Check:

   Conditions match desired height control [OK]

Hint: Ascend if below target, descend if above, else hold [OK]

Common Mistakes:

• Reversing ascend and descend speeds
• Removing else block causing no hold state
• Using <= or >= unnecessarily