Vehicle state reading (location, attitude, battery) in Drone Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of reading a vehicle's location in drone programming?

Reading a vehicle's location helps know where the drone is in the world, usually using GPS coordinates like latitude and longitude.

beginner

What does 'attitude' mean in the context of a drone's state?

Attitude refers to the drone's orientation in space, usually described by angles like pitch (tilt forward/back), roll (tilt side to side), and yaw (rotation around vertical axis).

beginner

Why is monitoring battery state important for drones?

Monitoring battery state ensures the drone has enough power to complete its mission and return safely, preventing crashes due to power loss.

intermediate

How can you read the battery level in a drone program?

You typically access a battery status property or method from the drone's API that returns the current battery percentage or voltage.

intermediate

What are common units used for location and attitude readings in drones?

Location is usually in degrees for latitude and longitude. Attitude angles are often in degrees or radians for pitch, roll, and yaw.

Which of these best describes 'attitude' in drone state reading?

A The drone's position on the map

B The drone's orientation angles like pitch, roll, and yaw

C The drone's battery percentage

D The drone's speed

Attitude means the drone's orientation in space, described by pitch, roll, and yaw angles.

What unit is commonly used to express a drone's location coordinates?

A Degrees

B Seconds

C Volts

D Meters

Location coordinates like latitude and longitude are expressed in degrees.

Why should a drone program check battery state regularly?

A To update the drone's location

B To calibrate the drone's sensors

C To measure the drone's speed

D To avoid running out of power mid-flight

Checking battery state helps prevent power loss that could cause crashes.

Which sensor data is NOT part of vehicle state reading in drones?

A Camera resolution

B Battery level

C Attitude angles

D GPS location

Camera resolution is not part of vehicle state reading like location, attitude, or battery.

What does the 'yaw' angle represent in drone attitude?

A Forward/back tilt

B Side to side tilt

C Rotation around vertical axis

D Altitude above ground

Yaw is the rotation of the drone around its vertical axis.

Explain how you would read and use the vehicle's location, attitude, and battery state in a drone program.

Think about what each piece of data tells you about the drone's current condition.

Why is it important to combine location, attitude, and battery readings when controlling a drone?

Consider how missing one of these could cause problems during flight.

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