> For the complete documentation index, see [llms.txt](https://yall.yassrobotics.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://yall.yassrobotics.com/documentation/tuning/crosshair-calibration.md).

# Crosshair Calibration

The crosshair is the reference point `tx`/`ty` (`LimelightTargetData.getHorizontalOffset()` / `getVerticalOffset()`) are measured against. If you're driving directly off `tx`/`ty` (visual servoing, not a full 3D pose), calibrating it correctly is what makes "`tx == 0`" actually mean "aligned with where I want to score," instead of just "aligned with the sensor's optical center."

## Single crosshair mode

Use this when your scoring position and camera angle don't vary.

1. Drive the robot to its ideal scoring location and rotation.
2. Click **Calibrate** in the Limelight web UI.
3. Verify: `tx`/`ty` should now read `0`/`0` when the robot is back in that exact position and rotation.
4. Recalibrate whenever you change field setup or camera mounting. For example, if a practice match reveals a better scoring position, recalibrate during the next lull.

## Dual crosshair mode

Use this for off-axis cameras or shooters that need real-time compensation as range changes. The effective crosshair interpolates between crosshair A and B based on target area.

1. Drive to the **closest** scoring position with ideal rotation, click **Calibrate** for crosshair A.
2. Drive to the **farthest** scoring position with ideal rotation, click **Calibrate** for crosshair B.
3. As the robot moves between those distances, the Limelight uses the target's area to interpolate between A and B automatically, with no additional code required.

{% hint style="info" %}
Crosshair calibration only affects `tx`/`ty` (and the values `LimelightTargetData` reads from them). It has no effect on 3D pose data (`getXXXPose_YYYSpace()`, `PoseEstimate`); that accuracy comes from [camera calibration](/documentation/tuning/charuco-camera-calibration.md) instead.
{% endhint %}

## See Also

* [Tuning Workflow Overview](/documentation/tuning/tuning-workflow-overview.md)
* [PID Tuning for Aiming & Ranging](/documentation/tuning/pid-tuning-for-aiming-and-ranging.md)


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