Livox LiDAR are very easy to integrate with OxTS INS devices. This guide will take you through setting the devices up and getting a pointcloud at the end.
Firstly, set up your devices on your vehicle such that the LiDAR and INS cannot move relative to one another and measure the relative angles and displacements between the devices' coordinate frames as accurately as possible. The accuracy of these measurements plays directly into the pointcloud accuracy. The INS measurement point is indicated on the device and the Livox is taken as the optical centre, not the IMU point which is not used.
Livox mounted with an xNAV650.
It is highly recommended that you use PTP with your Livox device. This feature can be enabled by a feature code that is purchased. This means that you only need to connect the devices via ethernet. If you are mobile mapping, it is probably best to use a network switch so that you can view the INS and Livox in real time. If you are UAV mapping, the Livox Avia requires a heartbeat that the INS does not provide (this will be developed later into OxTS firmware). The Livox device will natively be expecting to receive PTP messages making the integration extremely simple, all you need to do is connect the devices over ethernet and configure the INS to use PTP. The Livox uses the GPS time epoch.
The LiDAR Scanner tab of the Hardware Setup section in NAVconfig is not needed. NMEA messages are not required by the Livox.
Using NAVconfig 3.3 to configure PTP settings.
You will have to ensure that your devices are on the same IP range. This will be the case for the Livox and xNAV by default. However, configure also the ethernet port by opening Change Adapter Options to view the Network Connections window and right clicking your ethernet connection, selecting properties and then properties of Internet Protocol Version 4. Here you can add or change IP addresses to be on the correct range which will likely be 192.168.1.XXX.
Setting IP addresses in Network Connections.
Before setting off make sure you have checked the Livox is receiving PTP messages. This can be done in Livox Viewer, open device setting and you will see the status of PTP.
Livox Viewer showing PTP state is receiving 1588 signal.
If you are not seeing PTP being received, check your IP settings and ensure that both devices and your ethernet switch are on the same IP range (have the same first three numbers and a different last number), if this is the case, check in WireShark that PTP messages are being sent by the INS and received by the Livox.
WireShark stream ordered by protocol to view correct PTP messages.
Alternatively, you can use PPS for time synchronisation. To do this you will have to produce a custom cable to connect the INS and LiDAR which can have the benefit of bypassing the interface box or you can connect the bare wires from the INS user cable to the interface box. You can view the pinouts for receiving PPS in the Livox manual and the details of the OxTS cables in the INS manuals.
To record your data on the INS the process is as normal. An RD file is logged automatically and pulled off at the end of the survey. For recording Livox Avia data, you will need to keep Livox Viewer open, this is because a heartbeat is sent from the software to the Livox to keep it sending data. Connect the Livox device and press play to allow packets to start streaming. You can now see the LiDAR packets streaming in WireShark. Filter by the Livox IP address and simply record the data stream as a PCAP.
INS data is processed as normal using NAVsolve. Ensure that local coordinates have been enabled. Use the NCOM file and the VAT file that has been processed with the LiDAR data in Georeferencer to produce your pointcloud.
In Georeferencer, take your PCAP, NCOM and VAT and drag them into the files tab. Create an LIP and LIR file by clicking the plus signs. Select the LiDAR type in the dropdown. If you have used the wrong PTP time epoch, you can add the appropriate offset in the advanced commands as described in the Georeferencer manual.
Next, proceed to the Hardware configuration tab. Here you will need to input your measured displacements into the LIP fields. For the rotations, you will need to compare the coordinate axes of the blue cube to those of the Livox described in the Livox manual. Then rotate the cube to match the described orientation. For example:
Orient the blue cube to match the axes of the Livox relative to the INS for your setup.
When this is done, save changes.
The data is now ready to process a pointcloud by clicking 'Run Georeferencing'.
If you have performed a boresight calibration, then the boresight process in Georeferencer is the same as described in the guides. However, the reflectivity threshold for Livox is 150 for retroreflective objects so you will need to set the threshold to 150.
Targets as seen at a reflectivity threshold of 150 taken with the Avia.
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