Incorrect DepthPlanar Values from bottom_center Camera

[Joyymoonh]

Bug report

• AirSim Version/#commit: 1.8.1 (release binaries)
• UE/Unity version: Unreal Engine 4.27.2
• autopilot version: N/A (using SimpleFlight)
• OS Version: Windows 11 (22621.2134)

What's the issue you encountered?

When querying the bottom_center camera for a DepthPlanar image, the returned depth value at the pixel center is ~36.95 m larger than the expected geometric distance between the drone and the ground vehicle beneath it.

• Expected depth (based on ground-truth Z positions): 15.24 m
• Measured depth (center pixel of the planar depth image): 52.19 m

This discrepancy appears consistently across multiple runs and makes the depth image unreliable for any downstream tasks requiring metric accuracy.

Settings

settings.json gist

{
    "SettingsVersion": 1.2,
    "SimMode": "",
    "CameraDefaults": {
        "CaptureSettings": [
            { "ImageType": 0, "Width": 1920, "Height": 1080 },
            { "ImageType": 1, "Width": 1920, "Height": 1080 },
            { "ImageType": 3, "Width": 1920, "Height": 1080 },
            { "ImageType": 5, "Width": 1920, "Height": 1080 }
        ]
    },
    "ClockSpeed": 1.0,
    "Vehicles": {
        "test1_car": { "VehicleType": "PhysXCar", "X": 0, "Y": 0, "Z": 0, "ApiServerPort": 41461 },
        "test2_drone": { "VehicleType": "SimpleFlight", "X": -5, "Y": 0, "Z": 0, "ApiServerPort": 41471 }
    },
    "WindowWidth": 1920,
    "WindowHeight": 1080,
    "ClockType": "ScalableClock"
}

How can the issue be reproduced?

1. Download and extract AirSim 1.8.1 binaries for UE 4.27.2 on Windows 11.
2. Place the settings.json above next to the executable.
3. Start the Blocks environment (or any level with a flat ground plane).
4. Run the reproduction script (Python 3.9+ with airsim package installed).
5. Observe the console output showing the large depth mismatch.

Include full error message in text form

--- Depth Verification Results ---
  - Car Z (Ground Height): 0.60
  - Drone Z (Actual Height): -14.64
  - Expected Depth (Z Difference): 15.24 m
  - Measured Center Depth (Planar): 52.19 m

✗ [Failure] Measured depth is significantly different from expected depth!
  - Difference: 36.95 m