Range finder for terrain following in Drone Programming - Mini Project: Build & Apply

Range finder for terrain following

📖 Scenario: You are programming a drone to fly safely over uneven terrain. The drone uses a range finder sensor to measure the distance to the ground below. Your task is to process these sensor readings to help the drone maintain a steady height above the ground.

🎯 Goal: Build a simple program that stores range finder readings, sets a safe flying height threshold, filters readings that are too close to the ground, and then prints the safe distances for the drone to follow.

📋 What You'll Learn

Create a list called range_readings with exact distance values from the sensor.

Create a variable called safe_height to represent the minimum safe flying height.

Use a list comprehension to create a new list called safe_readings containing only readings greater than or equal to safe_height.

Print the safe_readings list to show the filtered safe distances.

💡 Why This Matters

🌍 Real World

Drones use range finders to avoid crashing into the ground when flying over hills or uneven surfaces. Processing these readings helps keep the drone at a safe height.

💼 Career

Understanding how to handle sensor data and apply filtering is important for drone programming, robotics, and any job involving real-time data processing.

1

Create the range finder data list

Create a list called range_readings with these exact distance values in meters: 3.5, 2.0, 4.8, 1.5, and 5.0.

Drone Programming

# Create the list range_readings with the given distances
# Your code here

Hint

Use square brackets [] to create a list and separate values with commas.

2

Set the safe flying height threshold

Create a variable called safe_height and set it to the value 3.0 to represent the minimum safe flying height in meters.

Drone Programming

range_readings = [3.5, 2.0, 4.8, 1.5, 5.0]
# Create the variable safe_height and set it to 3.0
# Your code here

Hint

Assign the number 3.0 to the variable safe_height using the equals sign =.

3

Filter safe range readings

Use a list comprehension to create a new list called safe_readings that contains only the values from range_readings that are greater than or equal to safe_height.

Drone Programming

range_readings = [3.5, 2.0, 4.8, 1.5, 5.0]
safe_height = 3.0
# Create safe_readings using list comprehension filtering values >= safe_height
# Your code here

Hint

Use the format [item for item in list if condition] to filter the list.

4

Display the safe readings

Print the safe_readings list to show the filtered safe distances for the drone.

Drone Programming

range_readings = [3.5, 2.0, 4.8, 1.5, 5.0]
safe_height = 3.0
safe_readings = [distance for distance in range_readings if distance >= safe_height]
# Print the safe_readings list
# Your code here

Hint

Use print(safe_readings) to display the list.

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