Overview

The CUST parameter group allows for defining arbitrary 3D rotations (Euler Angles) for sensor mounting.

While standard ArduPilot parameters (like AHRS_ORIENTATION or COMPASS_ORIENT) provide a list of preset rotations (e.g., Yaw90, Pitch180), these presets are typically limited to 45-degree or 90-degree increments. The CUST group enables precise alignment for sensors mounted at odd angles (e.g., a GPS mast tilted 15 degrees back).

Key Concepts

1. Enable Custom Rotation (CUST_ROT_ENABLE)

This master switch enables the custom rotation engine.

2. Defining the Rotation (CUST_ROTx_...)

You can define up to 2 unique custom rotations. Each is defined by a Roll, Pitch, and Yaw angle.

• Rotation 1: Used when AHRS_ORIENTATION (or other orientation param) is set to 100 (Custom 1).
• Rotation 2: Used when the parameter is set to 101 (Custom 2).

Parameter Breakdown

• CUST_ROT1_ROLL / PITCH / YAW: Euler angles for Custom Rotation 1.
• CUST_ROT2_ROLL / PITCH / YAW: Euler angles for Custom Rotation 2.

Integration Guide

Example: Tilted GPS

If you mount your GPS/Compass module on a mast that is tilted 30 degrees backward:

1. Set CUST_ROT_ENABLE = 1.
2. Set CUST_ROT1_PITCH = 30.
3. Set CUST_ROT1_ROLL and CUST_ROT1_YAW to 0 (assuming it faces forward).
4. Set COMPASS_ORIENT = 100 (Custom 1).
5. Reboot and verify the heading works correctly when you tilt the vehicle.

Developer Notes

• Library: libraries/AP_CustomRotations
• Math: Uses standard Euler sequence (Yaw -> Pitch -> Roll) to construct a rotation matrix.