> For the complete documentation index, see [llms.txt](https://docs-7.phoenixlidar.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs-7.phoenixlidar.com/lidarmill-desktop/workflow-kk/lidarsnap-v4/control-point-clouds.md).

# Control Point Clouds

Similar to using ground control with LiDARSnap, a control point cloud can be used as input for LiDARSnap. Below illustrates an example of resolving vertical offsets using a control point cloud:

<figure><img src="/files/7oNoUalneI9LAFqtjQha" alt=""><figcaption><p>Before Optimization - Red = Calibrated aerial dataset (Control cloud), Grey = Mobile point cloud from tightly coupled trajectory</p></figcaption></figure>

<figure><img src="/files/LOOJrn9obeDCqMVJAekv" alt=""><figcaption><p>After Optimization - Red = Calibrated aerial dataset (Control cloud), Grey = Mobile point cloud from LS4 optimized trajectory</p></figcaption></figure>

### Calibrating one dataset to another

Control point clouds can be particularly useful when one cloud is of a much higher accuracy and reliability than another cloud (e.g. using an aerial-acquired cloud as control when adjusting a mobile-acquired cloud). This process uses the **Calibrate Dataset to Another Dataset** mode:

<figure><img src="/files/taJCOpi4LlLFL3aGwLKR" alt=""><figcaption></figcaption></figure>

### Calibrating sensor to sensor within the same dataset

This mode is used for calibrating an auxiliary sensor, such as with multi-head mobile systems or systems that use a secondary sensor for SLAM navigation. *Within the same dataset* refers to the sensors' data both referencing the same trajectory:

<figure><img src="/files/zBbhXiPS2S9DOicK6Ax5" alt=""><figcaption></figcaption></figure>