Vehicle state reading (location, attitude, battery) in Drone Programming - Step-by-Step Execution

Concept Flow - Vehicle state reading (location, attitude, battery)

Start Vehicle State Read

↓

Read Location Data

↓

Read Attitude Data

↓

Read Battery Status

↓

Combine Data into State Object

↓

Return or Display State

↓

End

The program reads location, attitude, and battery data step-by-step, combines them, and outputs the vehicle state.

Execution Sample

Drone Programming

location = get_location()
attitude = get_attitude()
battery = get_battery_status()
vehicle_state = {
  'location': location,
  'attitude': attitude,
  'battery': battery
}
print(vehicle_state)

This code reads the vehicle's location, attitude, and battery, then prints the combined state.

Execution Table

Step	Action	Data Read	Variable Updated	Value
1	Call get_location()	Location coordinates	location	{'lat': 37.7749, 'lon': -122.4194, 'alt': 100}
2	Call get_attitude()	Attitude angles	attitude	{'roll': 0.1, 'pitch': -0.05, 'yaw': 1.57}
3	Call get_battery_status()	Battery info	battery	{'voltage': 11.1, 'percentage': 85}
4	Combine data into vehicle_state	N/A	vehicle_state	{'location': {...}, 'attitude': {...}, 'battery': {...}}
5	Print vehicle_state	N/A	Output	{'location': {'lat': 37.7749, 'lon': -122.4194, 'alt': 100}, 'attitude': {'roll': 0.1, 'pitch': -0.05, 'yaw': 1.57}, 'battery': {'voltage': 11.1, 'percentage': 85}}

💡 All vehicle state data read and combined, program ends.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
location	None	{'lat': 37.7749, 'lon': -122.4194, 'alt': 100}	{'lat': 37.7749, 'lon': -122.4194, 'alt': 100}	{'lat': 37.7749, 'lon': -122.4194, 'alt': 100}	{'lat': 37.7749, 'lon': -122.4194, 'alt': 100}	{'lat': 37.7749, 'lon': -122.4194, 'alt': 100}
attitude	None	None	{'roll': 0.1, 'pitch': -0.05, 'yaw': 1.57}	{'roll': 0.1, 'pitch': -0.05, 'yaw': 1.57}	{'roll': 0.1, 'pitch': -0.05, 'yaw': 1.57}	{'roll': 0.1, 'pitch': -0.05, 'yaw': 1.57}
battery	None	None	None	{'voltage': 11.1, 'percentage': 85}	{'voltage': 11.1, 'percentage': 85}	{'voltage': 11.1, 'percentage': 85}
vehicle_state	None	None	None	None	{'location': {...}, 'attitude': {...}, 'battery': {...}}	{'location': {'lat': 37.7749, 'lon': -122.4194, 'alt': 100}, 'attitude': {'roll': 0.1, 'pitch': -0.05, 'yaw': 1.57}, 'battery': {'voltage': 11.1, 'percentage': 85}}

Key Moments - 3 Insights

Why do we read location, attitude, and battery separately instead of all at once?

Each data type comes from different sensors or sources, so we read them step-by-step as shown in steps 1 to 3 in the execution_table.

What happens if one of the readings fails or returns None?

The variable for that reading stays None or empty, which means vehicle_state will have incomplete data. This is why each step updates variables separately (see variable_tracker).

Why do we combine all data into one vehicle_state object?

Combining makes it easy to manage and use all vehicle info together, as shown in step 4 and 5 of the execution_table.

Visual Quiz - 3 Questions

Look at the execution_table at step 2. What variable is updated and what value does it get?

A location with coordinates

B attitude with angles

C battery with voltage

D vehicle_state combined data

💡 Hint

Check the 'Variable Updated' and 'Value' columns at step 2 in the execution_table.

At which step is the vehicle_state object created by combining all data?

A Step 1

B Step 3

C Step 4

D Step 5

💡 Hint

Look for the step where 'Combine data into vehicle_state' is the action in the execution_table.

If the battery reading failed and returned None, how would the variable_tracker show battery after step 3?

A battery would remain None

B battery would have voltage and percentage values

C battery would have attitude values

D battery would be combined into vehicle_state anyway

💡 Hint

Refer to the variable_tracker row for battery and consider what happens if get_battery_status() returns None.

Concept Snapshot

Read vehicle state in steps:
1. Get location (lat, lon, alt)
2. Get attitude (roll, pitch, yaw)
3. Get battery status (voltage, %)
4. Combine all into one object
5. Use or display combined state

Full Transcript

This program reads the vehicle's location, attitude, and battery status one by one. First, it calls get_location() to get latitude, longitude, and altitude. Then, it calls get_attitude() to get roll, pitch, and yaw angles. Next, it calls get_battery_status() to get voltage and battery percentage. After reading all data, it combines them into a single vehicle_state object. Finally, it prints this combined state. Variables update step-by-step as shown in the execution_table and variable_tracker. This approach helps keep data organized and easy to use.

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