TV540 processing with LP360

1. Introduction

In this article we will explain step by step how to process a TV540 dataset in LP360 Drone. The idea of the article is to serve as a quick user guide on processing. This article will not explain in detail each of the settings available in each step, that can be found either in the help section or in the LP360 Drone User guide.

1.1. Pre-Requisites

Before starting with the workflow, the user will need to have LP360 v2024.2 or newer and the sensor extension. The sensor extension will be automatically downloaded the first time that the user tries to use the TV540 Data Copy tool or import a TV540 dataset.

Use the TV540 Data Copy tool to export raw data from the TV540 sensor to your computer. Export the raw data following the steps described in the TrueView 3DIS Processing Workflow ->TV540 Data Copy

Make sure to select a working directory before starting the workflow, to do that. Go Project Settings ->Global ->LP360 Working Directory ->Select a folder in your local hard drive

The working directory is a folder that LP360 will use during the TV540 processing to create temporary files that will be deleted after the processing is completed. Make sure to have at least 200GBs of space in the folder’s hard drive selected. It is also recommended to select the folder in your local hard drive since working from a remote hard drive or a server may crash/delay the processing.

2. Import

1- Open LP360 v2024.2.13 or newer
2- Select "Import Raw Missions into New Project..."
3- Select "TrueView / Microdrones"
4- Press "Folder" to import the raw data from the sensor. You can select 1 or more cycles (flights) to be process in the same project.
Note: the very first time you select TV540 data the software will ask you to install the LP360 sensor extension.

Tip: Remember that the data needs to be downloaded first from the sensor using TV540 data copy tool.
5- Press Next
6- Select the base station file in Rinex format --> Next
7- Select the Project Root Folder and the Project Name
8- Select the desired CRS

Tip: If you do not know the CRS, you can always select WGS84 UTM zone XX in Ellipsoidal heigh. LP360 shows the recommended UTM zone.
9- Press Next --> The summary will be display --> Press next
10- Data imported

3. Point Cloud generation

3.1. Trajectory Processing

1- Go to "Sensor" ribbon--> Trajectory Processing --> Next

2- In the base station section --> Press "Survey Nail" --> Press "Add"
3- Add the base station coordinates (latitude, longitude, heigh in meters and datum) --> Press "OK" --> Press "OK"

4- Review the Antenna Height and the APC Offset
Tip: If the "APC Offset" is in red means that LP360 was not able to identify the offset of the antenna. Then add manually the value. If you do not know the offset value, you can get it at NOAA antenna calibration.
5- Press "Next"
6- Review the Trajectory Processing summary --> Press "Submit" --> A confirmation window will appear, press "Continue"
7- Go to "Job manager" to monitor the processing status

8- Once the job is completed, it will appear as "Ready" in the "Job manager" --> Select it--> Press "Complete Job"

3.2. Flight lines generation

Once the data is processed, LP360 allows you to create flight lines. This step involves selecting the portions of the data you need, excluding unnecessary segments like takeoffs and turns, and ensuring that you only work with the most relevant data.

1. Select the Auto-Create Flight Lines tool on the Sensor tab (Figure 63) to open the Auto Create Flight Lines dialog.
            
   
   • Flight Line Layer - The name of the layer that will be created and requires no input from the user.
   • Min. Length – No linear set of points shorter than this value will be considered for the calculation of a flight line. This number should usually be set to the shortest flight line length. Use the Measure tool  on the main LP360 toolbar to measure the shortest desired flight line.
   • Turn Radius – The radius, in map units, to allow at turns. The smaller the number, the closer the flight lines will be cut to the turns. The greater the radius, the larger the gap.
   • Max Deviation – The deviation parameter that tells the software when to break a line segment into two. The smaller this number, the more linear the flight lines but the more flight lines that will be created. The larger this value, the more “bend” will be allowed in a relatively straight segment without splitting. Hence, increase this value significantly if you have curved flight lines.
2. Once you have entered the desired parameters (Figure 65), select Compute Flight Lines. The number of flight lines created will then populate in the Flight Lines column and the Status will change to Computed. Once satisfied, click Next.
   
3. On the Edit Mode page of the Auto Create Flight Lines dialog, the Select/Edit Features tool will automatically be enabled.
   
   • Select flight lines you wish to delete, then click the Delete key then the Enter key on your keyboard.
     • Hold control while selecting to select multiple flight lines. Or drag to select multiple flight lines.
   • After editing the flight lines, the Status will change to Edited to indicate a change has been made. Any edits made within Edit Mode will automatically be saved.
4. The flight line layer should be created, and the flight lines displayed in blue in the map view.
   • Results can be changed by changing the parameters and selecting Compute Flight Lines again. The existing lines will be replaced with the results from the new settings.

3.3. Post Processing point cloud

1- Go to Sensor ribbon --> Post Processing tool
2- Select the Clip Angle
Tip: clip angles is 50% of the FOV, if we select 37 deg clip angle means 74 deg FOV. The maximum TV540 LiDAR FOV is 75 degrees. I recommend using the maximum FOV with the TV540.
3- Select the Clip Range
Tip: If you want to generate all the points with no filter, uncheck "Clip Angle" and "Clip Range".

4- Run Post Processing ...

Post processing will generate a the point cloud divided by flight lines.

4. Strip Align

The next step will be to verify the alignment of the flight lines and correct it. For that we should perform cross sections in the overlap areas between flight lines. It is recommended to perform this sections in flat areas, buildings are especially useful for it.
We can also use tools like "Surface Precision" to verify the alignment across the flight or between multiple flights. After we have verify the alignment, we proceed to correct it.
Strip Align tool requires the license addon "Strip Align"

1- Go to Sensor ribbon --> Strip Align
2- Select the LAS to align.
Tip: You can select multiple flights. If you do it, the tool will correct any misalignment between flights. However, if one flight has significant error (or bias), it will introduce error into the new Strip Align layer.
3- Press "Submit Strip Align job"

4- Go to "Job manager" --> Check the processing status
5- Once Strip Align finish the status will change to "Ready" --> Select the job--> Click "Complete job"

Strip Align will create a new LAS, in my case it is called "LAS_SA". This new LAS has all the misalignments corrected. Example:

After this step we recommend continuing with the True View recommended workflow. Some of the steps recommended are "Smoothing", "Control Points", "Outliers removal" or "Ground Classification".