Vehicle state reading (location, attitude, battery) in Drone Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Reading vehicle location coordinates

What is the output of this code snippet that reads the vehicle's latitude and longitude?

Drone Programming

vehicle_location = {'lat': 37.7749, 'lon': -122.4194}
print(f"Latitude: {vehicle_location['lat']}, Longitude: {vehicle_location['lon']}")

A Latitude: -122.4194, Longitude: 37.7749

B Latitude: 37.7749, Longitude: -122.4194

C Latitude: 37.7749 Longitude: -122.4194

D Latitude: None, Longitude: None

💡 Hint

Check the keys used to access latitude and longitude in the dictionary.

The dictionary keys 'lat' and 'lon' correctly access the latitude and longitude values respectively. The f-string formats them with labels and a comma.

❓ Predict Output

intermediate

Output of vehicle attitude reading

Given the vehicle attitude dictionary, what will this code print?

Drone Programming

attitude = {'roll': 0.1, 'pitch': -0.05, 'yaw': 1.57}
print(f"Roll: {attitude['roll']}, Pitch: {attitude['pitch']}, Yaw: {attitude['yaw']}")

A Roll: 0.1, Pitch: -0.05, Yaw: 1.57

B Roll: 0.1 Pitch: -0.05 Yaw: 1.57

C Roll: 1.57, Pitch: 0.1, Yaw: -0.05

D Roll: None, Pitch: None, Yaw: None

💡 Hint

Check the order and keys used in the f-string.

The keys 'roll', 'pitch', and 'yaw' correctly access the attitude values. The f-string prints them with commas separating each value.

❓ Predict Output

advanced

Battery percentage calculation output

What is the output of this code that calculates battery percentage from voltage?

Drone Programming

voltage = 11.1
min_voltage = 10.5
max_voltage = 12.6
percentage = int((voltage - min_voltage) / (max_voltage - min_voltage) * 100)
print(f"Battery: {percentage}%")

A Battery: 28%

B Battery: 44%

C Battery: 70%

D Battery: 80%

💡 Hint

Calculate the fraction of voltage between min and max, then multiply by 100.

The formula calculates the battery percentage using int((voltage - min_voltage) / (max_voltage - min_voltage) * 100). Here, (11.1 - 10.5) / (12.6 - 10.5) * 100 = 0.6 / 2.1 * 100 ≈ 28.57, which int() truncates to 28. Therefore, it prints "Battery: 28%".

❓ Predict Output

advanced

Vehicle attitude dictionary key error

What error does this code raise when trying to access vehicle attitude?

Drone Programming

attitude = {'roll': 0.1, 'pitch': -0.05}
yaw = attitude['yaw']
print(yaw)

A No error, prints 0

B TypeError: unsupported operand type(s)

C KeyError: 'yaw'

D NameError: name 'yaw' is not defined

💡 Hint

Check if the key 'yaw' exists in the dictionary.

The dictionary does not have the key 'yaw', so accessing attitude['yaw'] raises a KeyError.

🧠 Conceptual

expert

Interpreting combined vehicle state output

Given this combined vehicle state dictionary, what is the value of 'battery_status' after running the code?

Drone Programming

vehicle_state = {
  'location': {'lat': 40.7128, 'lon': -74.0060},
  'attitude': {'roll': 0.0, 'pitch': 0.0, 'yaw': 0.0},
  'battery': {'voltage': 11.4, 'min_voltage': 10.5, 'max_voltage': 12.6}
}
voltage = vehicle_state['battery']['voltage']
min_v = vehicle_state['battery']['min_voltage']
max_v = vehicle_state['battery']['max_voltage']
percentage = int((voltage - min_v) / (max_v - min_v) * 100)
battery_status = 'OK' if percentage > 30 else 'LOW'
print(battery_status)

A LOW

B Error

C None

D OK

💡 Hint

Calculate the battery percentage and compare with 30.

Battery percentage = (11.4 - 10.5) / (12.6 - 10.5) * 100 = 0.9 / 2.1 * 100 ≈ 42.85, which is greater than 30, so battery_status is 'OK'.

Practice

1. What does the vehicle.location.global_frame property represent in drone programming?

easy

A. The drone's battery percentage

B. The drone's current GPS coordinates (latitude, longitude, altitude)

C. The drone's orientation angles (roll, pitch, yaw)

D. The drone's speed in meters per second

Solution

1. Step 1: Understand the property name

   vehicle.location.global_frame refers to the drone's global position in the world.

2. Step 2: Identify what global_frame means

   Global frame means GPS coordinates: latitude, longitude, and altitude.

3. Final Answer:

   The drone's current GPS coordinates (latitude, longitude, altitude) -> Option B

4. Quick Check:

   Location = GPS coordinates [OK]

Hint: Global frame means GPS location, not battery or angles [OK]

Common Mistakes:

• Confusing location with battery status
• Mixing attitude (orientation) with location
• Thinking global_frame is speed

2. Which of the following is the correct way to read the drone's battery level in percentage using the vehicle object?

easy

A. battery_level = vehicle.battery.remaining

B. battery_level = vehicle.battery.level

C. battery_level = vehicle.battery.level_percent

D. battery_level = vehicle.battery.percent

Solution

1. Step 1: Recall the battery property

   The vehicle object uses vehicle.battery.remaining to get battery percentage.

2. Step 2: Check other options

   Other options like percent, level, or level_percent are not valid properties.

3. Final Answer:

   battery_level = vehicle.battery.remaining -> Option A

4. Quick Check:

   Battery percentage = vehicle.battery.remaining [OK]

Hint: Battery percentage is in vehicle.battery.remaining [OK]

Common Mistakes:

• Using incorrect property names like percent or level
• Confusing battery with location or attitude properties
• Assuming battery is a method, not a property

3. Given the code snippet:

attitude = vehicle.attitude
print(f"Roll: {attitude.roll}, Pitch: {attitude.pitch}, Yaw: {attitude.yaw}")

What will this code output if the drone is perfectly level and facing north?

medium

A. Roll: 0.0, Pitch: 1.57, Yaw: 0.0

B. Roll: 0.0, Pitch: 0.0, Yaw: 1.57

C. Roll: 0.0, Pitch: 0.0, Yaw: 0.0

D. Roll: 1.57, Pitch: 0.0, Yaw: 0.0

Solution

1. Step 1: Understand attitude values for level drone

   A perfectly level drone has roll and pitch near 0 radians, yaw depends on heading.

2. Step 2: Facing north means yaw is 0 radians

   Yaw angle 0 means facing north, so yaw = 0.0.

3. Final Answer:

   Roll: 0.0, Pitch: 0.0, Yaw: 0.0 -> Option C

4. Quick Check:

   Level drone facing north = all zeros [OK]

Hint: Level means roll and pitch zero; north means yaw zero [OK]

Common Mistakes:

• Assuming yaw is 1.57 (90 degrees) for north
• Mixing roll and pitch values
• Confusing radians with degrees

4. Identify the error in this code snippet that tries to print the drone's altitude:

altitude = vehicle.location.global_frame.altitude
print(f"Altitude: {altitude} meters")

medium

A. The property global_frame does not have altitude

B. The print statement syntax is incorrect

C. Altitude should be accessed from vehicle.attitude

D. vehicle.location.global_frame is None before GPS lock

Solution

1. Step 1: Check property availability

   vehicle.location.global_frame.altitude is valid but may be None if GPS is not locked.

2. Step 2: Understand None value issue

   If GPS lock is missing, global_frame is None, so accessing altitude causes error.

3. Final Answer:

   vehicle.location.global_frame is None before GPS lock -> Option D

4. Quick Check:

   GPS lock needed before reading altitude [OK]

Hint: Check if global_frame is None before accessing altitude [OK]

Common Mistakes:

• Assuming altitude is in attitude object
• Ignoring NoneType errors when GPS not ready
• Thinking print syntax is wrong

5. You want to create a function that returns a dictionary with the drone's current latitude, longitude, altitude, roll, pitch, yaw, and battery percentage. Which code snippet correctly does this?

hard

A. def get_state(vehicle):
return {
'lat': vehicle.location.global_frame.lat,
'lon': vehicle.location.global_frame.lon,
'alt': vehicle.location.global_frame.altitude,
'roll': vehicle.attitude.roll,
'pitch': vehicle.attitude.pitch,
'yaw': vehicle.attitude.yaw,
'battery': vehicle.battery.remaining
}

B. def get_state(vehicle):
return {
'lat': vehicle.location.global_frame.latitude,
'lon': vehicle.location.global_frame.longitude,
'alt': vehicle.location.global_frame.altitude,
'roll': vehicle.attitude.roll_angle,
'pitch': vehicle.attitude.pitch_angle,
'yaw': vehicle.attitude.yaw_angle,
'battery': vehicle.battery.percent
}

C. def get_state(vehicle):
return {
'lat': vehicle.location.global_frame.lat,
'lon': vehicle.location.global_frame.lon,
'alt': vehicle.location.global_frame.altitude,
'roll': vehicle.attitude.roll,
'pitch': vehicle.attitude.pitch,
'yaw': vehicle.attitude.yaw,
'battery': vehicle.battery.level
}

D. def get_state(vehicle):
return {
'latitude': vehicle.location.global_frame.latitude,
'longitude': vehicle.location.global_frame.longitude,
'altitude': vehicle.location.global_frame.altitude,
'roll': vehicle.attitude.roll,
'pitch': vehicle.attitude.pitch,
'yaw': vehicle.attitude.yaw,
'battery': vehicle.battery.remaining
}

Solution

1. Step 1: Check property names for location and attitude

   Correct properties are lat, lon, altitude for location and roll, pitch, yaw for attitude.

2. Step 2: Verify battery property and dictionary keys

   Battery percentage is vehicle.battery.remaining. Keys can be short names like 'lat', 'lon', 'alt'.

3. Final Answer:

   The code using correct property names (lat, lon, altitude, roll, pitch, yaw, battery.remaining) -> Option A

4. Quick Check:

   Use correct property names and battery.remaining [OK]

Hint: Use lat, lon, altitude, roll, pitch, yaw, battery.remaining [OK]

Common Mistakes:

• Using wrong property names like latitude or percent
• Mixing attitude property names with _angle suffix
• Using battery.level instead of battery.remaining