Exercise 1: Split Trajectory and Point Cloud
Before calculating boresight error parameters using Automatic Adjustment or Manual Measurement approach, the point cloud needs to be split by trajectories.
1 Launch LiDAR360 and load the StripAlignmentSampleData.LiData file to the project.
2 Under Strip Alignment in the toolbar, click Strip Alignment to open the Strip Alignment window.
If Strip Alignment is not found in the toolbar, click Windows and click Strip Alignment to add it to the toolbar.
3 In Strip Alignment window, set working directory:
Output files will be placed in the working directory folder.
If LiAcquire was used to process the trajectory and the point cloud, the processed trajectory file is under the LiAcquire project folder > LiNav > POSProc > LiNav_Result.pos.
4 Click Open Trajectory File and select the Trajectory.pos file.
5 In the Open Trajectory Files window, under Info tab, match the columns with data headers as following:
The GridX and GridY columns are used when the point cloud is in a local dataset, such as the sample dataset. If the dataset does not have GridX and GridY column, a coordinate system that matches the coordinate system of your point cloud needs be selected.
LiDAR360 supports two trajectory file formats, .pos and .out.
6 Click Apply.
7 In Strip Alignment window, click Draw Polygon , and draw a polygon on top of the point cloud.
8 Click Split Trajectory .
9 The split trajectories will be displayed in different colors, and each one will be added as one record to the trajectory list in Strip Alignment window.
10 Only the trajectories within the planned survey flight will be used in the Strip Alignment process. Therefore, select the unwanted trajectories, and use the Delete Trajectory Files button to delete them.
11 Click Yes to permanently delete the files.
- Click Yes: the trajectory files will be deleted from the drive.
- Click No: the trajectories are removed from the current project, but the files are not deleted from the drive.
For the Strip Alignment Tool to eliminate boresight errors in the LiDAR data, the associated split trajectories need be parallel and adjacent trajectories splits need to have heading directions that are opposite (+/-180 degrees) on each other.
12 Click Cut Point Cloud Based on Trajectories . In the Select Point Cloud File window. Make sure the StripAlignmentSampleData.LiData file is selected, and click OK.
13 Click Yes to Add data to current project. The split point cloud datasets are added to Layers.
14 Click Match Point Cloud And Trajectory .
15 Under Layers, uncheck the StripAlignmentSampleData.LiData layer, and you will see the colored point clouds.
16 Turn on EDL in Display toolbar to introduce depth effect in the data.
17 Click Profile on toolbar to open the Profile Editor window.
18 Click Profile tool in Profile Editor window. Draw a cross-section line over the building rooftop where laser scan data matched with all three parallel trajectory splits can be found. The cross-section line should be perpendicular to the to the horizontal slopes of the three parallel trajectories splits (red, blue, and white in this tutorial).
19 Adjust the Buffer to 0.1 and press Enter: .
20 In the Profile [Focus] viewer below, you may zoom in to examine the current alignment qualities of the trajectories.
21 Repeat the steps above to examine alignment quality of other areas in the project before any corrections.