# LiDARSnap v4

## Video Walkthrough

In this video, we cover the LiDARSnap 4 module in SpatialExplorer 6. LiDARSnap is used for point cloud optimization and trajectory optimization.

{% embed url="<https://www.youtube.com/watch?v=BKZUMjn3jqM>" %}

## Written Walkthrough

* Within the Project window, click on the pointcloud filename, click on the "Edit" tab, and then click on the LiDAR Snap icon to access [LIDARSnap v4 (LS4)](https://docs.phoenixlidar.com/lidarmill-desktop/user-interface/windows/project-management-window/point-clouds#lidarsnap).&#x20;

![LiDAR SNAP tool for Point Cloud Calibration](/files/-M_WgXcwuOLZDa5jsoK1)

### General

* Under the "General" Tab, select desired flightline intervals to calibrate
* After Interval selection, it is recommended to use LS4 default settings to perform a boresight calibration
* If a new boresight calibration is not desired, uncheck "Optimize Mounting Rotation"
* Specify an output directory for the LS4 report and move onto the "Sensor tab"

![](/files/-M_Wj7jio7t3B-DD-YVC)

### Sensor

* Under the "Sensor" Tab, it is recommended to use LS4 default settings to perform a boresight calibration
* If a new boresight calibration is not desired, leave all options unchecked.&#x20;
* Move on to the "Trajectory Tab"&#x20;

![](/files/-M_WjCiwrGpeB1hbwSrg)

### Trajectory&#x20;

* **Trajectory optimization** is also an option for point cloud calibration and often refines the post processed trajectory even further than the original processing through feedback with the point cloud.&#x20;
* Vertical optimization is the recommended parameter as GNSS observations are least accurate in the z direction, although the user has the option to utilize all translation and orientation variables through three different optimization models: **Bias**, **Spline Efficient**, and **Spline Full**.
* Select the desired Optimization Model
* For boresighting, it is recommended to use all default settings
* For trajectory optimization only, uncheck "Disable Mounting Optimization During Trajectory Optimization"&#x20;
* Move on to "Ground Control" Tab.&#x20;

![](/files/-M_WjGwDKOr--ZEbjhqi)

### Ground Control

* **Adjustment to Ground Control** allows the user to select one or multiple GCP datasets to allow the point cloud calibration to vertically adjust the point cloud to match the surface derived from the GCPs.
* Note: This process shifts individual flightline lidar swaths to best align with Ground Control. The recommended process is to vertically translate the entire lidar pointcloud to GCPs, and this is covered under the "Ground Control" tool .
* Move on to "Tuning" Tab

![](/files/-M_WjQBzkoT9-lu0lreX)

### Tuning

* Under the "Tuning" tab, it is recommended to leave all settings as default
* Move on to the "Misc" Tab.&#x20;

![](/files/-M_WjVb3Ko3FPNuVqXD2)

### Misc

* Under the "Misc" tab, it is recommended to leave all settings as default.
* Click "OK" to begin LS4 processing

![](/files/-M_Wjb4H1xNA5SgHgpBK)

### LiDAR Calibration Parameters

* Upon completion of LiDAR Snap, a new trajectory is created in the specified directory and loaded to the project window under "Trajectories"
* This trajectory is activated and the point cloud is automatically [recomputed](https://docs.phoenixlidar.com/lidarmill-desktop/user-interface/windows/project-management-window/point-clouds#recompute-points) using the updated calibration values. &#x20;
* Calibration values can be viewed by clicking on the lidar sensor within the Project window, clicking on the wrench icon at the lower left, and then clicking on the "[Calibration](https://docs.phoenixlidar.com/lidarmill-desktop/user-interface/windows/project-management-window/lidars/ldr-x#calibration)" tab.&#x20;

![](/files/-Ma-SVQtc4JhEzqZfYWo)

![Calibration of LiDAR sensor through use of z translations and tilt angle offset calculations](/files/-MXiUG8vlZprYHinamDg)

* The result is a point cloud produced with sensor and mission specific calibrations and refinements to deliver the most accurate cloud possible.&#x20;


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