Velodyne HDL-64E S3 Operating instructions

USER’S MANUAL AND
PROGRAMMING GUIDE
HDL-64E S3
High Definition LiDAR Sensor

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High Definition LiDAR Sensor
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Table of Contents
Safety Notices ....................................................................................................................... 4
Caution ...................................................................................................................................... 4
Introduction .......................................................................................................................... 5
In the Box................................................................................................................................... 5
Principles of Operation .......................................................................................................... 6
Installation ............................................................................................................................ 8
Mounting.................................................................................................................................... 8
Wiring ........................................................................................................................................ 8
Power ..................................................................................................................................... 8
Lockout Circuit........................................................................................................................ 8
Ethernet.................................................................................................................................. 8
Serial Interface RS-232........................................................................................................... 8
View Image ........................................................................................................................... 9
1. Use the Included Point-cloud Viewer...................................................................................... 9
2. Develop Your Own Application-Specific Point-Cloud Viewer ................................................... 9
Change Run-Time Parameters.............................................................................................. 12
Sample Batch File (.bat)............................................................................................................12
Sample SERCMD.txt file...........................................................................................................12
Available Serial Commands HDL-64E S3 .................................................................................13
Control the Spin Rate................................................................................................................14
Change Spin Rate in Flash Memory ......................................................................................14
Change Spin Rate in RAM Only.............................................................................................14
Limit Horizontal FOV Data Collected.........................................................................................14
Define Sensor Memory IP Source and Destination Addresses..................................................15
Dual Returns.............................................................................................................................15
Laser Output Power Level Management and Reporting............................................................17
Noise Level Adjustment ............................................................................................................17
Upload Calibration Data............................................................................................................18
External GPS Time Synchronization.........................................................................................18
Packet Format and Status Byte for GPS Time Stamping .......................................................19
Timestamp Accuracy Rules and Accuracy.............................................................................19
Laser Firing Sequence and Timing............................................................................................20
Firmware Updates ............................................................................................................... 21
Appendix A: Mechanical Drawings ...................................................................................... 22
Appendix B: Connector Pin outs .......................................................................................... 25
Power, Serial & GPS Connector ...............................................................................................25
Ethernet Connector...................................................................................................................25
Appendix C: Digital Sensor Recorder (DSR).......................................................................... 26
Install DSR................................................................................................................................26
Calibrate DSR...........................................................................................................................26
Live Playback............................................................................................................................26
Record Data..............................................................................................................................27
Playback Recorded Files ..........................................................................................................27
DSR Key Controls.....................................................................................................................28

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Appendix D: MATLAB Sample Code..................................................................................... 29
Calibration and Sensor Parameter Data....................................................................................30
Appendix E: Data Packet Format ......................................................................................... 31
Data Packet Overview...............................................................................................................31
Status Type Rotation.................................................................................................................32
Status Value Example for Status Types of H, M, S, D, N, Y, G, T and V:...............................32
GPS Status Values...................................................................................................................33
GPS Timestamp Conversion Example......................................................................................33
Status Type Calibration and Unit Parameters ...........................................................................33
Warning Status Bits ..................................................................................................................38
CRC Checksum Algorithm ........................................................................................................39
Last Six Bytes Examples...........................................................................................................39
Appendix F: Dual Two Point Calibration Methodology & Code Samples............................... 43
Coordinate Calculation Algorithm Sample Code........................................................................43
Intensity Compensation vs Distance .........................................................................................45
Calibration Window...................................................................................................................45
Intensity Value Corrected by Distance ......................................................................................46
Appendix G: Ethernet Timing Tables ................................................................................... 47
Sensor Ethernet Transmit Timing Tables ..................................................................................47
How to Use the Timing Tables...............................................................................................47
Laser and Detector Arrangement ......................................................................................... 49
Lasers as Seen from the Back of the Unit.................................................................................49
Laser as Seen on the Wall........................................................................................................49
Appendix I: Angular Resolution........................................................................................... 50
Appendix J: Troubleshoot ................................................................................................... 51
Appendix K: Service and Maintenance ................................................................................ 52
Appendix L: Specifications .................................................................................................. 53

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Safety Notices
Caution
To reduce the risk of electric shock and to avoid violating the warranty, do not remove cover (or back).
Refer servicing to qualified service personnel.
The lightning flash with arrowhead symbol is intended to alert the user to the presence of uninsulated
“dangerous voltage” within the product’s enclosure that maybe of sufficient magnitude to constitute a risk
of electric shock to persons.
The exclamation point symbol is intended to alert the user to the presence of important operating and
maintenance (servicing) instructions in the literature accompanying the product.
1. Read Instructions— All safetyand operating instructions should be read before the product is
operated.
2. Retain Instructions — The safety and operating instructions should be retained for future
reference.
3. Heed Warnings — All warnings on the product and in the operating instructions should be
adhered to.
4. Follow Instructions — All operating and use instructions should be followed.
5. Servicing — The user should not attempt to service the product beyond what is described in the
operating instructions. All other servicing should be referred to Velodyne.

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High Definition LiDAR Sensor
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Introduction
Congratulations on your purchase of a Velodyne HDL-64E S3 High Definition LiDAR Sensor. These
sensors represent a breakthrough in sensing technologyby providing more data points regarding the
surrounding environment than previously possible.
NOTE: The HDL-64E S3 High Definition LiDAR sensor is referred to for brevity as “the sensor” throughout
this manual.
This manual and programming guide
covers:
. Installation and wiring
. The data packet format
. The serial Interface
. Software updates
. GPS
. Viewing the data
. Programming information
HDL-64E
S3
Lower Laser Block Upper Laser Block Vertical Field
of
View (VFOV) Primary Application
32 lasers separated by
1/2o vertical
spacing
32 lasers separated
by
1/3o vertical
spacing
+2° to 24.8°
Autonomous
navigation
For the latest updates to this manual
— check www.velodynelidar.com.
In the Box
Each shipment contains:
. Sensor
. CD with
○Calibration file .xml file
○DSR viewer software
○MATLAB program for reading calibration parameters from the sensor
○User’s Manual and Programming Guide

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Principles of Operation
The sensor has 64 lasers fixed mounted on upper and lower laser blocks, each housing 32 lasers. Both
laser blocks rotate as a single unit. With this design each of the lasers fires tens of thousands of times per
second, providing exponentiallymore data points/second and a more data-intensive point cloud than a
rotating mirror design. The sensor delivers a 360o horizontal Field of View (HFOV) and a 26.8o vertical
FOV.
Additionally, state-of-the-art digital signal processing and waveform analysis are employed to provide high
accuracy, extended distance sensing and intensity data. The sensor is rated to provide usable returns up
to 120 meters. The sensor employs a direct drive motor system with no belts or chains in the drive train.
See the specifications at the end of this manual for more information about sensor operating conditions.
Figure 1: HDL-64E S3 Design Overview

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360°
Spinning
Lidar
Sensor
26.8°
Valid Data Range
0.9 m to 120 m
(3’ to 394
’ )
Uncalibrated Point
Cloud Data Packets
Calibrated Point
Cloud Data as 3D
image
Digital Sensor
Recorder and
Viewer Software
XML Laser
Calibration File
Figure 2: LiDAR System Overview

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Installation
The unit is simple to install because the sensor has multiple mounting options and uses standard wiring
connectors.
Mounting
The sensor base provides the following mounting options:
. Side and/or front mount
. Top and/or bottom mount
The sensor can be mechanicallymounted at any angle with respect to its base. Vertical mounting is
recommended for navigation applications. Refer to Appendix A for mechanical drawings with complete
dimensions and sensor mounting suggestions.
. For all mounting options, mount the sensor to withstand vibration and shock without risk of
detachment.
. The sensor should be vibration isolation mounted from the vehicle frame.
. Mounting location may require a protective shield around the rotating unit to block debris from
hitting the motor area.
. Allow clearance behind the connector side of the unit, so there is room to install and remove
the cables. (See drawing in Appendix A.)
. The sensor is weatherproofed to withstand wind, rain and other adverse weather conditions.
The spinning nature of the sensor helps it shed excess water from the front window that could
hamper
performance.
Wiring
Cables are not provided. The end-user needs to fabricate cables with the mating connectors to those on
the sensor. Refer to the wiring diagram in Appendix B.
Power
THE SENSOR IS RATED FOR 10 - 32 VOLTS DC. Any voltage applied over 32 VDC may damage the
sensor even though the sensor does have over voltage protection.
NOTE: The sensor doesn’t have a power switch. The sensor is operational whenever power is applied.
Lockout Circuit
The sensor has a lockout circuit that prevents its lasers from firing until it achieves a preset operational
RPM.
Ethernet
M12 D-CODED connector is provided on the unit. Velodyne recommends using a category 6 cable
(shielded, twisted pair) for the Ethernet cable.
NOTE: The sensor is only compatible with network cards that have either MDI or AUTO MDIX capability.
Serial Interface RS-232
The serial interface is incorporated into the main connector, a standard Deutsch connector. The RS-232
interface is used to apply RS-232 serial commands as well as apply firmware updates.

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View Image
The sensor needs no configuration, calibration, or other setup to begin producing viewable data.
However, you need to apply the calibration file to set the accuracy of the data. Once the unit is mounted
and wired, supplying power to the sensor will cause it to start scanning and producing data packets.
Data points may be viewed by either of the following methods:
1. Use the included point-cloud viewer (DSR Viewer)
2. Develop you own application-specific point-cloud viewer
1. Use the Included Point-cloud Viewer
The quickest way to view the data collected as a live image is to use the included Digital Sensor Recorder
(DSR) application. DSR is Velodyne’s point-cloud processing data viewer software. DSR reads in the
packets from the sensor over Ethernet, performs the necessary calculations to determine point locations
and then plots the points in 3D on your PC monitor. Both distance and intensity data can be observed
through DSR. If you have never used the sensor before, this is the recommended starting point. For
more on installing and using DSR, see Appendix C.
2. Develop Your Own Application-specificPoint-cloud Viewer
Many users elect to develop their own application-specificpoint cloud tracking and plotting and/or storage
scheme, which requires these fundamental steps:
1. Establish communication with the sensor.
2. Create a calibration table either from the calibration data included in-stream from the sensor or
from the included .xml data file.
3. Parse the packets for rotation, block, distance and intensity data
4. Apply the calibration factors to the data.
5. Plot or store the data as needed.
The following provides more detail on each of the above steps.
1. Establish communication with the sensor.
The sensor broadcasts its data via UDP packets. By using a network monitoring tool, such as
Wireshark, you can capture and observe the packets as they are generated by the sensor. See
Appendix E for the UDP packet format. The default source IP address for the sensor is
192.168.3.43, and the destination IP address is 192.168.3.255. To change the IP configuration,
see the Define Sensor Memory IP Source and Destination Addresses section.
2. Create an internal calibration table either from the calibration data included in-stream from the
sensor or from the included .xml data file.
This table must be built and stored internal to the point-cloud processing software. The easiest
and most reliable way to build the calibration table is by reading the calibration data directly from
the UDP data packets. A MatLab example of reading and building such a table can be found in
Appendix D, and on the CD included with the sensor.
Alternatively, the calibration data can be found in the included .xml file found on the CD included
with the sensor. A description of the calibration data is shown in the following table.

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.xml Calibration
Parameters
Parameter Unit Description Values
rotCorrection degree The rotational correction angle for
each laser, as viewed from the back
of the sensor.
Positive factors rotate to the
left. Negative values rotate to
the right.
vertCorrection degree The vertical correction angle
for
each
laser, as viewed from the back
of the sensor.
Positive values have the laser
pointing up. Negative values
have the laser pointing down.
distCorrection cm Far distance correction of each
laser distance due to minor laser
parts’ variances.
Add directly to the distance
value read in the packet.
distCorrectionX cm
Close distance correction in X of
each laser due to minor laser parts
variances interpolated with far
distance correction then applied to
measurement in X.
distCorrectionY cm
Close distance correction in Y of
each laser due to minor laser parts
variances interpolated with far
distance correction then applied to
measurement in Y.
vertOffsetCorrection cm The height of each laser as
measured from the bottom of the
base.
One fixed value for all upper
block lasers. Another fixed
value for all lower block lasers.
horizOffsetCorrection cm The horizontal offset of each laser
as viewed from the back of the
laser.
Fixed positive or negative
value for all lasers.
Maximum Intensity
Value from 0 to 255. Usually
255.
Minimum Intensity Value from 0 to 255. Usually 0.
Focal Distance
cm
Maximum intensity distance.
Focal Slope The control intensityamount.
The calibration table, once assembled, contains 64 instances of the calibration values shown in
the table above to interpret the packet data to calculate each point’s position in 3D space.
Use
the
first 32 points for the upper block and the second 32 points for the lower block. The rotational
info found in the packet header is used to determine the packets position with respect to the 360o
horizontal field of view.
3. Parse the packets for rotation, block, distance and intensity data.
Each sensor’s data packet has a 1206-byte payload consisting of 12 blocks of 100 byte firing data
followed by 6 bytes of calibration and other information pertaining to the sensor.
Each 100-byte record contains a block identifier and then a rotational value followed by 32 3-byte
combinations that report on each laser fired for the block. Two bytes report distance to the
nearest 0.2 cm, and the remaining byte reports intensity on a scale of 0 to 255. 12 100-byte
records exist, therefore, 6 records exist for each block in each packet. For more on packet
construction, see Appendix E.

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4. Apply the calibration factors to the data.
Each of the sensors’s lasers is fixed with respect to vertical angle and offset to the rotational
index data provided in each packet. For each data point issued by the sensor, rotational and
horizontal correction factors must be applied to determine the point’s location in 3D
space
referred
to by the return. Intensityand distance offsets must also be applied. Each sensor comes
from Velodyne’s factory calibrated using a dual-point calibration methodology, explained further in
Appendix F.
NOTE: The minimum return distance for the sensor is approximately3 feet (0.9 meters). Ignore
returns closer than this.
NOTE: A file on the CD called “HDL Source Example” shows the calculations using the above
correction factors. This DSR uses this code to determine 3D locations of sensor data points.
5. Plot or store the data as needed.
For DSR, the point-cloud data, once determined, is plotted onscreen. The source to do this can
be found on the CD and is entitled “HDL Plotting Example.” DSR uses OpenGL to do its plotting.
You may also want to store the data. If so, it may be useful to timestamp the data so it can be
referenced and coordinated with other sensor data later. The sensor has the capabilityto
synchronize its data with GPS precision time. For more in this capability, see the
Externa l GPS
Time Synchronization section.

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Change Run-Time Parameters
The sensor has several run-time parameters that can be changed using the RS-232 serial port. For all
commands, use the following serial parameters:
. Baud 9600
. Parity: None
. Data bits: 8
. Stop bits: 1
NOTE: All serial commands, except one version of the spin rate command, store data in the sensor’s
flash memory. Data stored in flash memorythrough serial commands is retained during firmware updates
or power cycles.
The sensor has no echo back feature, so no serial data is returned from the sensor. Commands can be
sent using a terminal program or by using batch files (e.g. .bat). A sample .bat file is shown below.
Sample Batch File (.bat)
MODE COM3: 9600,N,8,1 COPY SERCMD.txt COM3 Pause
Sample SERCMD.txt file
This command sets the spin rate to 0300 RPM and stores the new value in the unit’s flash memory.
#HDLRPM0300$

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Available Serial Commands HDL-64E S3
More information about these commands is on the pages following the table below.
Command Description Parameters
#HDLRPMnnnn$ Set spin rate from 0300 to 1200 RPM in flash
memory. (default is 0600 RPM) •nnnn is an integer between 0300 and 1200
#HDLRPNnnnn$
Set spin rate from 0300 to 1200 RPM in RAM (default is
0600 RPM) •nnnn is an integer between 0300 and 1200
#HDLIPAssssssssssssdddddddddddd$ Change source and/or destination IP address.•ssssssssssss is the source 12-digit IP address
•dddddddddddd is the destination 12-digit IP
address
#HDLFOVsssnnn$ Change horizontal Field of View (HFOV).
•tsss = starting angle in degrees; sss is an
integer between 000 and 360
•nnn = ending angle in degrees; nnn is an
ineger between 000 and 360
#HDLRETS$ Strongest return only, this is the default setting.
#HDLRETB$ Both strongest and last returns. If the strongest return is equal to the last return, the next strongest return is
reported.
#HDLRETL$ Last return only.
#HDLPWRA0$ Set auto power for all lasers with return of 8-bit laser raw intensity level and 3-bit laser power output.
#HDLPWRFn8$ Set fixed power for all lasers, with return of 8-bit laser raw
intensity level and 3-bit laser power.
•n =0 - 7
#HDLPWRA8$ Set auto power for all lasers with return of 8-bit laser normalized intensity level and no laser power output. In the
return, the raw intensity data is normalized by the calibration parameters.
#HDLTHDuuulll$ Noise level adjustment. •uuu = upper block noise level
•lll = lower block noise level
Velodyne LiDAR, Inc. ©2019 63-HDL64ES3 REV K

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Control the Spin Rate
Change Spin Rate in Flash Memory
The sensor can spin at rates ranging from 0300 RPM (5 Hz) to 1200 RPM (20 Hz). The default is 0600
RPM (10 Hz). Changing the spin rate does not change the data rate -
the unit sends out the same
number of packets (at a rate of
~ 1.3 million data points per second) regardless of its spin rate. The
horizontal image resolution increases or decreases depending on rotation speed.
See the
Angu l ar Reso l ution section found in Appendix I for the angular resolution values for various spin
rates.
To control the sensor’s spin rate, issue a serial command of the case sensitive format #HDLRPMnnnn$
where nnnn is an integer between 0300 and 1200. The sensor immediatelyadopts the new spin rate. You
don’t need to power cycle the unit, and the new RPM is retained with future power cycles.
Change Spin Rate in RAM Only
If repeated and rapid updates to the RPM are needed, such as for synchronizing multiple sensors
controlled by a closed loop application, you can adjust the sensors’ spin rates without storing the new
RPM in flash memory(this preserves flash memoryover time).
To control the sensor’s spin rate in RAM only, issue a serial command of the case sensitive format
#HDLRPNnnnn$ where nnnn is an integer between 0300 and 1200. The sensor immediatelyunit adopts
the new spin rate. You shouldn’t power cycle the sensor as the new RPM is lost with future power cycles,
which returns to the last known RPM.
Limit Horizontal FOV Data Collected
The sensor defaults to a 360o surrounding view of its environment. It may be desirable to reduce this
horizontal field of view (HFOV) and, hence, the data created.
To limit the horizontal FOV, issue a serial command of the case sensitive format #HDLFOVsssnnn$
where:
. sss = starting angle in degrees; sss is an integer between 000 and 360
. nnn = ending angle in degrees; nnn is an integer between 000 and 360
The HDL unit immediatelyadopts the new HFOV angles without power cycling and retains the new HFOV
settings upon power cycle.
NOTE: Regardless of the FOV setting, the lasers always fire at the full 360o HFOV. Limiting the HFOV
only limits data transmission to the HFOV of interest.

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The following diagram shows the HFOV from the top view of the sensor.
Examples of HFOV Command Settings
Case 1: FOV
0° to 360 °
FOV command: #HDLFOV000360$
Case 2: FOV
0° to 90 °
FOV command: #HDLFOV000090$
Case 3: FOV
-90 ° to 90°
FOV command: #HDLFOV270090$
Top View of Sensor
Define Sensor Memory IP Source and Destination Addresses
The sensor comes with the following default IP addresses:
. Source: 192.168.3.043
. Destination: 192.168.3.255
To change either of the above IP addresses, issue a serial command of the case sensitive format
#HDLIPAssssssssssssdddddddddddd$ where
. ssssssssssss is the source 12-digit IP address
. dddddddddddd is the destination 12-digit IP address
Use all 12 digits to set an IP address. Use 0 (zeros) where a digit would be absent. For example,
192168003043 is the correct syntax for IP address 192.168.3.43.
The unit must be power cycled to adopt the new IP addresses.
Dual Returns
Different environmental conditions require a different priority of the type of distance point returns. Hence,
you can define which distance points (strongest, last or both) have the return priority. This feature is also
known as dual returns.
The packet structure remains unchanged regardless of the option selected.
. Strongest: This is the normal case.
. Last: Poor visibility conditions, such as fog and dust, benefit from collecting the distance
return values based on the “last return” scenario. The near field occluding atmosphere is
ignored and the furthest surface return produces a valid distance point. The packet reporting
format remains unchanged for this option.
. Both: The firmware searches for the strongest and last returns and saves them in a data
packet. In the data packet, the strongest signal is in blocks 1, 3 and 5; the last return is in
blocks 2, 4 and 6. If the strongest signal also happens to be the last signal, the 2nd strongest
signal is output.
NOTE: If the “Last” or “Both” option is selected, the packet data rate increases to 2.1 million data points
per second (MDPS), although the effective point reporting density falls to 1.05 MDPS.

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To activate dual returns and set the return priority, issue a serial command of the case sensitive format:
. #HDLRETS$ Strongest return only, this is the default setting.
. #HDLRETL$ Last return only.
. #HDLRETB$ Both strongest and last returns. If the strongest return is equal to the last
return, the next strongest return is reported.
Example: A box is 5 meters from the sensor. The laser partially hits the box and gets the strongest signal. Another box
is 20 meters from the sensor. The laser partiallyhits the second box and generates the last return. The sensor is not
moving, so the returns generate circle patterns.
Both Strongest and Last Returns Only Strongest Return Only Last Return
NOTE: The X, Y, Z and distance figures at the bottom of the image represent the distance of the x, y, z
crosshairs with respect to the origin point indicated by the small white circle. The concentric gray circles
and grid lines represent 10 meter increments from the sensor.

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Laser Output Power Level Management and Reporting
Under poor visibility conditions, such as fog and dust, setting the laser output to full power can be
beneficial. You can toggle the output power between AUTO (the default setting), or set a fixed value for
all lasers from 0 and 7 (with 7 being full power).
NOTE: Setting the power level to 7 is recommended when using the “last return” priority for distance
points.
To set the laser output power level and information returned in the data packet:
. #HDLPWRA0$ Set auto power for all lasers with return of 8-bit raw laser intensity level and
3-bit laser power output.
. #HDLPWRFn8$ Set fixed power for all lasers, where n =0 - 7, with return of 8-bit laser raw
intensity level and 3-bit laser power. The 8 in the command indicates that the 8-bit raw
intensity is always returned.
. #HDLPWRA8$ Set auto power for all lasers with return of 8-bit laser normalized intensity
level and no laser power output.
Serial
Command
for Laser Output Power
Distance Data Low Byte Intensity Data Byte
#HDLPWRA0$
Reports Distance
Power
(0-7)
Intensity
(raw data)
(0-255)
Bit 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1
#HDLPWRFn8$
Reports Distance
Power
(0-7)
Intensity
(raw data)
(0-255)
Bit 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1
#HDLPWRA8$
Reports Distance
Intensity
(data normalized
by
calibration parameters)
(0-255)
Bit 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1
Noise Level Adjustment
The Avalanche Photo Diode detectors for the HDL-64E are extremelysensitive. Some users have
experienced spurious primary or secondaryreturns from a random light source. For each return, the DSP
conducts a full waveform analysis. Returns below a certain noise floor are ignored. To adjust this noise
floor, use the command below.
#HDLTHDuuuIII$ where
. uuu = upper block noise level
. III = lower block noise level
The default threshold is 024 for both the upper and lower blocks. A lower noise threshold allows more
returns, thus spurious light sources may cause a return to be reported (especially a secondary return). A
higher noise level reports fewer returns, but may ignore legitimate returns.

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Upload Calibration Data
Sensors used the .xml file exclusivelyfor calibration data. The calibration data found in the .xml file can
be uploaded and saved to the unit’s flash memory by following the steps outlined below.
1. Locate the HDLCAL.bat, loadcal.exe, and .xml files on the CD and copy them to the same
directory on your PC connected to the sensor.
2. Edit HDLCAL.bat to ensure the copy command lists the right COM port for RS-232
communication with the sensor.
3. Run HDLCAL.bat and ensure successful completion.
4. The sensor received and saved the calibration data.
5. Verifythe successful upload of the calibration data by checking that the date and time of the
upload have been updated. Refer to Appendix E for where in the data packets this data can be
located.
You can also upload calibration data from the .xml file into flash memoryand use GPS time
synchronization.
External GPS Time Synchronization
The sensor can synchronize its data with precision GPS-supplied time pulses so you can ascertain the
exact firing time of each laser in any particular packet. The firing time of the first laser in a particular
packet is reported in the form of microseconds since the top of the hour, and from that time each
subsequent laser’s firing time can be derived via the table published in Appendix H and included on the
CD.
Calculating the exact firing time requires a GPS receiver generating a sync pulse and the $GPRMC
NMEA record over a dedicated RS-232 serial port. The output from the GPS receiver is connected via a
cable to the Deutsch connector on the sensor. The sensor integrates the NMEA record into the data
packets with the corrected timestamp based on the sync pulse. The sensor data occurs at a much faster
rate than the sync pulse, so the sensor must also count the microseconds between the synch pulses
when determining the corrected timestamps. The GPS receiver needs to be supplied by the customer to
provide the required sync pulse and NMEA record.
The GPS device must have the following characteristics:
. Issue a once-a-second synchronization pulse, typically output over a dedicated wire.
. Configure an available RS-232 serial port to issue a once-a-second $GPRMC NMEA record.
No other output can be accepted by the
sensor.
. Issue the sync pulse and NMEA record sequentially.
. The sync pulse length is not critical (typical lengths are between 20ms and 200ms)
. Start the $GPRMC record between 50ms and 500ms after the end of the sync pulse.
. Configure the $GPRMC record either in the hhmmss or hhmmss.s format.

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Packet Format and Status Byte for GPS Time Stamping
The 6 bytes at the end of the data packet report GPS timing and synchronization data. For every packet,
the last 6 bytes are formatted as follows:
Timestamp Bytes in Reverse Order in microseconds
Bytes Description Notes
4
GPS
timestamp 32 bit unsigned integer timestamp. This value represents microseconds from
the top of the hour to the first laser firing in the packet.
1 Status
Type 8 bit ASCII status character as described in Appendix E. The status byte
rotates through many kinds of sensor information.
1 Status
Value
8 bit data as described in Appendix E.
Within the GPS status byte, there are 4 GPS status indicators:
. 0: No GPS connection.
. A: Both PPS (synch) and GPS command have signal.
. V: Only GPS command signal, no PPS (synch).
. P: Only PPS (synch) signal, no GPS time command.
Timestamp Accuracy Rules and Accuracy
The following rules and subsequent accuracy apply for GPS timestamps:
GPS Connection
Timestamp Info Accuracy Notes
GPS isn’t
connected (GPS
Status 0)
The sensor starts running on
its own clock starting at
midnight Jan 1 2000. This
date and time data is
reflected in the H, M, S, D,
N, and Y data values.
Expect a drift of about 5
seconds/day.
The sensor clock
does not correct for
leap years. See
Appendix E for more
information.
GPS is connected
The H, M, S, D, N, and Y
data values are obtained
from the $GPRMC NMEA
record.
GPS time synching runs in
one of two modes:
. The GPS is used first.
The accuracyis of the
GPS device employed.
. When the GPS
achieves
lock, the
sensor clock is then
within +/-50µs of the
correct time at all times.
GPS is
disconnected
after being
connected
The sensor continues to run
on its own clock.
Expect drift of about 5
seconds/day

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High Definition LiDAR Sensor
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Laser Firing Sequence and Timing
If the GPS timestamp feature is used, it can be useful to determine the exact firing time for each laser so
as to properlytime-align with the other data sources.
The upper block and lower block collect distance points simultaneously, with each block issuing one laser
pulse at a time. That is, each upper block laser fires in sequence and in unison with a laser from the lower
block.
Lasers are numbered sequentiallystarting with 0 for the first lower block laser to 31 for the last lower
block laser; and 32 for the first upper block laser to 63 for the last upper block laser. For example, laser
32 fires simultaneouslywith laser 0, laser 33 fires with laser 1, and so on.
The sensor has an equal number of upper and lower block returns. Hence, when interpreting the delay
table, each sequential pair of data blocks represents the upper and lower block respectively. Each upper
and lower block data pair in the Ethernet packet has the same delay value.
Six firings of each block takes 139 µs and then the collected data is transmitted. It takes 100 µs to transmit
the entire 1248 byte Ethernet packet. This is equal to 12.48 Bytes/µs and 0.080128 µs/Byte. See Appendix
E for more information.
A timing table, shown in Appendix G, shows how much time elapses between the actual capturing of a
distance point and when that point is output from the device. By registering the event of the Ethernet data
capture, you can calculate back in time the exact time at which any particular distance point was captured.