General Data Acquisition with SpatialExplorer
If you are using a GNSS reference station, ensure that it is set up in location with a clear view of the sky away from buildings and powerlines and properly configured to log raw observations of at least GPS+GLONASS at 1 Hz during the entire scanning procedure. Refer to Reference Station Setup.
It’s important to ensure that your IMU to GNSS antenna offset measurements are within an appropriate range before initiating a mapping mission. If these measurements are not within an acceptable range, it will cause a mismatch between uncertainty values (position and attitude), which will make it difficult to obtain a proper IMU alignment solution. Before powering on rover, we recommend verifying the IMU to GNSS antenna offset measurements. Refer to IMU to GNSS Antenna Offsets.
The system must have GNSS reception to track time and thus activate the LiDAR sensor.
Ensure that your rover is set to the correct profile if you have multiple (aerial, ground 30 deg mount, etc.) before the mission begins.
Workflow
1. Place your UAV at the takeoff site. If the system includes a Velodyne LiDAR sensor, take the cap off the LiDAR sensor.
Removing the sensor cap will allow you to scan at a temperature closer to the calibration temperature of the sensor.
2. Provide power to the Phoenix LiDAR system with either the UAV’s power or from a backup battery. We recommend using the UAV’s power as your main source and only temporarily using the battery power for “hot swapping” scenarios such as maintenance.
Primary power will be drawn from the source with the highest voltage.
3. Power on the Phoenix LiDAR system. The CPU will turn on automatically when power is supplied to the MR30 input connector.
In a rare case where the CPU button does not light up after power has been supplied, the CPU can manually be turned on using the CPU button.
4. Launch SpatialExplorer and connect to the rover to monitor the system. If connecting to the rover as a TCP client, make sure to use the correct Rover Hostname; via ethernet use rover-wire or via Wi-Fi use rover-wifi. If you are connecting to the rover over a 3G/4G cellular connection, choose the Phoenix LiDAR Systems connection service and enter the corresponding license key. Refer to Connect to Rover for more information.
5. Leave the system powered on and idle at its departure site for a period of 5-10 minutes.
If you have a Scout Series NavBox: LONG press the SENSOR button on the system to power on the LiDAR sensor. If the system includes a Velodyne LiDAR sensor, it must warm up for a period of 5-10 mins.
If your system is capable of static alignment, the system will determine its heading and the navigation system status (INS) in SpatialExplorer will switch from "Aligning" to "Alignment Complete" during this time.
Static alignment uses the average of the sensor output, therefore it is imperative for the vehicle to remain completely stationary for the duration of the alignment.
6. Initiate UAV takeoff and hover at comfortable height.
7. If you have a mapping system with a Basler camera, you must set the exposure to automatic in SpatialExplorer before initiating the flight, while the rover is hovering at a comfortable height. In SpatialExplorer, locate the Basler camera in the Sensors window and right click to bring up a menu of camera options unique only to Basler cameras. Set the “ExposureAuto” and “GainAuto” options to Continuous. Repeat this procedure for any remaining Basler cameras. Refer to Sensor Controller for more information.
This will allow the camera to set its exposure and gain levels continuously to match the desired scanning environment during the flight. Failure to do so will result in overexposed captured images.
8. Kinematic Alignment: To perform a kinematic alignment maneuver, you must travel forward for a period of at least 10 seconds, at a minimum velocity of 5 m/s (18 km/h), moving as straight and as level as possible with an unobstructed clear line of sight. Refer to IMU Alignment and Alignment Routines for more details on Static and Kinematic Alignment.
We recommend performing kinematic alignment regardless if you've already statically aligned your system.
You will notice the navigation system status (INS) in Spatial Explorer switch from "Aligning" to "AlignmentComplete" indicating that the heading has been determined with sufficient certainty.
9. Figure Eights: You must conduct two to three sets of figure-eights, either manually or using waypoint mode to stabilize the navigation system and obtain an INS status of "SolutionGood" in SpatialExplorer. This allows the software to process the current IMU drift and noise. We recommend flying a figure eight pattern because it helps lower the covariances (Uncertainty Position and Uncertainty Attitude), which are estimated errors of position and attitude. Refer to Navigation System Stabilization for more details.
Always keep the vehicle direction of flight pointing forward, much like an airplane. As you're flying, the Uncertainty Position (UncertP) and Uncertainty Attitude (UncertA) are both visible in progress bars. The lower the values the better.
10. Activate Sensors: After achieving an INS status of "SolutionGood" and lower covariance values, activate the sensors (camera, LiDAR, etc.) within SpatialExplorer and begin scanning your flight.
We highly recommend flying straight to obtain smooth scan lines throughout the scan area. Furthermore, avoid sharp turns and extreme elevation changes, and turn only at the perimeter of your scan area. Using autopilot will result in the best scan results. Data acquired during turns will be much less accurate.
11. Once you’ve finished scanning your flight, deactivate the sensors from within SpatialExplorer.
12. Mirror Beginning and End Alignment Procedures: Before landing, if you intend to post-process the trajectory for increased accuracy, you must conduct another two to three sets of figure eights, and then travel forward for a period of at least 10 seconds (kinematic alignment), at a minimum velocity of 5 m/s (18 km/h), moving as straight and as level as possible with an unobstructed clear line of sight.
15. Land the UAV, but do not move it from its landing spot. Before shutting down a multilaser sensor (Velodyne), you must turn the LiDAR sensor OFF (LONG press the sensor button on NavBox).
16. Leave the rover static for a period of about 5-10 minutes to allow the IMU to obtain a reliable static alignment. During this period, the IMU must be completely static.
17. With the flight complete, shut down the rover using the “Shutdown Rover” radio button in SpatialExplorer and check the "Power off onboard computer" box. Alternatively, the CPU button on the NavBox can be used to shut down the system.
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