Velodyne Acoustics HDL-32E APPendix d caLiBration and orientation, Calibration and Orientation

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aPPendix d: caLiBration and orientation

HDL-32E User’s Manual

Calibration and Orientation

There are six axes of variation when determining the exact location of any given laser firing for the HDL-32. The axes are x, y, z, along with rotational, horizontal, and vertical angles.

X, Y, Z. Both x and y offsets are zero and are calculated from the centerline of the device. The Z location of the firing should be considered to be the distance from the bottom of the base plane to the center of the lenses, or 3.575 inches (9.0805 cm).

Figure D1.

The device isn’t calibrated at the factory for angular accuracy. The angular precision is 1/100 of a degree, and the device should repeat to this level of accuracy. There are provisions for a pair of dowel pins to be located in the mating fixture, and this will provide repeatability in case the device is removed and remounted. The reason for this is that the device needs to be calibrated in situ to whatever defines either the x or y axis of the vehicle.

The HDL-32E’s laser spots are aligned at the factory to be within 1/2” of their true position at 100 feet. Therefore, no calibration of either the deflection (horizontal) or rotational angle is necessary – both the horizontal angle and rotational laser angles are always zero.

The vertical angle of each laser is described in the XML file supplied with each unit and as listed above. This is the only calibration parameter necessary to plot points in 3D space, so for the HDL-32E all db.xml calibration files are identical and contain only the vertical angle values as listed above.

Laser Spot Size

The lasers project a well defined rectangular shaped spot that is approximately 4” wide by 2” tall at 100’ distance. The spot size at the source of the HDL-32 is approximately 1/2” wide by 1/4” tall, causing the angular divergence to be 2.79 milliradians.

Distance Calibration

Distance calibration parameters are programmed into the HDL-32E firmware – no external adjustment for distance is needed. The HDL-32E uses ((1023/1024) * 300,000,000 meters/sec) as the reference speed of light. However, as the true speed is affected by local atmospheric conditions, the unit uses a closed-loop timing compensation scheme that calibrates each laser continuously and is the primary compensation for thermally induced timing corrections.

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Contents HDL-32E E R ’ S M a N U a L a N DCoordinate Calculation Algorithm Sample Code Digital Sensor Recorder DSRHDL-32E Sample Data Packets Calibration and OrientationPage Introduction PrinciPLes of oPeration Principles of OperationMount Base SetuPCase Contents Operate Connect Power and ComputerWiring WeatherIP Address UsaGeHDL-32 MAC ID and IP address format Mac ID UsaGe GPS Receiver Option 2 Customer’s GPS Receiver External GPS Time SynchronizationGPS Receiver Option 1 Velodyne Supplied GPS Receiver Images below show the GPS receiver included with the HDL-32E Laser Timing Packet Format and Status Byte for GPS Time StampingTime Stamping Accuracy Rules Vertical angle Laser Firing SequenceFiring order SerVice and Maintenance TrouBLesHootinGProblem Resolution SPecifications Calibrate InstallAPPendix a diGitaL sensor recorder dsr Live PlaybackAPPendix a Playback of Recorded filesShift ZoomAxis Rotation RotationalAPPendix B HdL-32e saMPLe data PacKets Data Packet FormatAPPendix B Positioning Packet Figure B2Figure B3 Time Stamp Nmea SentenceEthernet Packet Example APPendix c coordinate caLcuLation aLGoritHM saMPLe code Laser Spot Size APPendix d caLiBration and orientationCalibration and Orientation Distance CalibrationAPPendix e etHernet transit tiMinG taBLe Velodyne LiDAR, Inc
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