The technique we use to derive centimeter level precision is called Real Time Kinematic Global Navigation Satellite System (RTK GNSS). This system uses the satellite signal’s carrier wave in addition to the information content of the signal and relies on a single GNSS reference station to provide real-time corrections. Now what happens during short periods of GNSS outages? Enter the Inertial Navigation System (INS): the INS uses a computer, motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate the position, orientation, and velocity of the system. In order to combine the two systems, a very sophisticated algorithm, known as a linear quadratic estimation (LQE), operates on streams of noisy sensor data to produce a statistically optimal estimate of the system’s position at any point in time. By fusing this information with the LIDAR data, a point-cloud is generated and visualized in real-time using Phoenix Aerial SpatialExplorer.
In case real-time corrections from the GNSS reference station are not available or longer outages prevent transmission of data to Rover, a third party software package called Inertial Explorer™ can still produce a precise trajectory in post-processing. Both types of trajectories (either generated in real-time from the INS or from Inertial Explorer™ in post-processing) can be fused with LIDAR data with Phoenix Aerial SpatialFuser to create point clouds in LAS format.
The AL2 is engineered to attach to almost any vehicle and for the first time, the accompanying software is just as flexible as the module. By splitting sensor control and user interface into separate parts, multiple mapping options are possible:
The AL2 can be used for mapping with many different vehicles such as UAV’s, gyrocopters, fixed-wing aircraft, etc. As shown in the image above, the operator is typically on the ground and connected directly to the GNSS reference station. Using the Phoenix Aerial SpatialExplorer software, the operator transmits correction data to the AL2 via a long range WiFi system. The AL2 then fuses this data in real time and transmits a down-sampled pointcloud back to the operator.
When the operator travels with the AL2 in a car, boat or ATV, he/she can connect directly to the AL2 using either WiFi or an ethernet cable. Correction data can then be transmitted from the GNSS reference station to SpatialExplorer software via long range WiFi or a public IP adress (using e.g. 3G/4G). With the on-board 240 gig SSD hard drive, the operator can scan for 6 hours without having to stop to download the data.
Pheonix Aerial Advantages
The ability to visualize real time point clouds brings several key advantages:
The operator can immediately determine if the results match the expectations. Previously, results were available only after landing, in which case it becomes very time consuming and expensive to make any changes.
The operator can visualize the growing point cloud on a computer screen in real time and with this data can locate areas yet to be scanned and quickly alter the UAV’s course.
Via 4G network, the operator can remotely share his/her screen with clients in real time to confirm/alter LiDAR pointcloud.
Total System Configuration
UAV hardware Specification
S1000 with 1200 motor
A2 with New GPS PRO
One Futaba 10CHG with R6208
6* “dual pack” Battery and fly at least 10mins
carrying case for whole set UAV
LiDar Hardware Specification
Velodyne VLP-16 Puck
Class 1 eye safe laser
Accuracy: Linear error: ± 2cm at 25m or lower
Scan rate: at least 300,000 points per second
Measurable range: at least 100m at 10Hz
At least 16 laser channels
Field of view: 360° (Horizontal) and 30° (±15° Vertical)
Weight: less than 700g
Onboard data storage: at least 15 minutes
POS Hardware Specification
Dual-frequency RTK-GNSS receivers with at least GPS and GLONASS support for position acquisition
Support dual GNSS antenna for precise heading acquisition: GPS (L1, L2), GLONASS (L1, L2)
Support Fiber Optic Gyro type Inertial Measurement Unit (IMU) for attitude acquisition (KVH 1725 IMU orequivalent)
GNSS update rate: 20Hz or above
IMU update rate: 200Hz or above
Bias Offset: =< 5 deg/hr
Initialization time: =< 3s
Position Accuracy (RMS) in post-processing mode with outrage duration of 0 second: 0.01m (Horizontal) and 0.02m (Vertical)
Velocity Accuracy (RMS) in post-processing mode with outrage duration of 0 second: 0.02m/s (Horizontal) and 0.01m/s (Vertical)
Attitude Accuracy (RMS) in post-processing mode with outrage duration of 0 second: 0.015° (Roll), 0.015° (Pitch) and 0.080° (Heading)
**everything mount on the S1000 and sync together**