Decoding Notes

Data is always broadcast via UDP packets using a LAN network . It is advisable to use a fast (at least 100Mbit) network card, due to real-time scanning and the huge amount of data.

The maximum expected number of beams per second for the VLP-16 is about 300 000 (three hundred thousand).

The actual raw data stream is Velodyne's proprietary format. This document does not describe this format.

The VLP-16 has configured two UDP Ports in order to output data: only port 2368 is used by this driver, containing time-tagged laser firing data.

The other port 8308, with MEMS accelerometers' and gyros' values, is not used by this driver or Qinsy.

Timing

Due to network characteristics in general, and because of latency inside the scanner, time stamping upon arrival will result in inaccurate and variable timing.
Therefore timing via Time Synchronization (formerly PPS) pulse from GPS is highly recommended.

This means that your laser unit must be interfaced to an external Time Synchronization pulse from a GNSS receiver and a UTC time-tag message from the same receiver.

With this scanner it can be done quick and easy, using the interface box that comes with your VLP-16:

It is important that Qinsy is also interfaced to a Time Synchronization system, so all systems will operate within the same time frame.

Network Setup

All communication to and from the laser unit goes via a LAN network which is accessible through the same interface box as used for the GNSS/Time Synchronization timing (see above).

The exact LAN IP address of the laser unit should be provided by the manufacturer or your re-seller, or it should be stated in the documentation that comes with your scanner. Normally Velodyne configures their laser units with IP address 192.168.1.201.

The LAN IP address of your computer's network should be in the same range, except for the last digit. This must be a unique number! In the example below the value 100 is used. Use for the subnet mask the values 255.255.255.0

It is recommended to check the network connection between your computer and the laser unit before commencing any scan operation. You may do this by using the ping command from the Windows Command Prompt:

Select Start from the Windows task bar, Run..., Cmd <Enter>, and 'ping' the IP address of your laser unit.
The network connection is okay when you receive a reply three times within a few milliseconds.

Web GUI Control

When there is a successful network connection, you could also use a standard web browser in order to communicate directly with the scanner and set some initial settings.

When you enter the IP address of the scanner in the address bar of the browser (most likely http://192.168.1.201/), the following page should appear:

• First important setting to check is that Laser is On .
• Secondly, this is the only place to set the spin rate (horizontal turns). Default Motor RPM is 600 (10 Hz), but any value between 300 (5 Hz) and 1200 (20 Hz) is allowed.
• Last thing to check is whether GPS/Timing is accepted by the scanner. In the bottom panel you should see your current geographical co-ordinates for the GPS Position. More important is that the PPS status is Locked .

Database Setup

Internally the driver is treated as a multibeam system, creating multibeam 'xyz' observations, therefore you will find the laser system drivers under category type Multibeam Echosounders.

('multibeam' versus 'laser scanning'-terminology: ping = scan = swath = line, footprint = pixel = pulse = return)

1. Edit System Wizard

2. Multibeam Echosounder Parameters 

Example Mobile Scanning Setup
 

In this example the unit is mounted on the rear of a car with the cable pointing downward and tilted 90 degrees in order to scan the road. So make sure to select in the online setup for the Scanner Mounting setting "Backward Tilted, Cable Down".
In that case the default alignment offsets will stay 0° (Roll, Pitch and Heading).

3. Echosounder Accuracy Parameters

• You may leave all values on the third wizard page at their defaults.

4. Multibeam Echosounder Corrections

• You may leave all values on the last wizard page at their defaults.

Online

Hardly any other control is needed for this type of laser scanner. Once you power it up, it starts rotating, scanning and broadcasting the data automatically.

Use the Web GUI to set the standard settings (e.g. spin rate), for some additional other control settings you can use the Qinsy Controller:

Select Echosounder Settings, click on the Laser System icon, and select the 'Control' tab page.

Control	Device Settings
Connected	In order to communicate with the scanner, the driver must make a network connection first. This attempt to connect will always be done automatically when going online. No This means that there is no UDP network connection between the driver and the laser unit, and therefore no laser firing data will be received. Yes Check this every time you go online with the Controller, in order to communicate with the scanner. If no connection could be made, a notification message will be displayed in the Events list. Under normal circumstances a connection will be established within a second. [ Set to Not Connected at startup ] Select this option (only once, and hit the Apply button) if you want to disable the 'Auto Connect' option. This means that every time you go online with the Controller, you must make a connection yourself by selecting 'Yes' from this list. [ Set to Auto Connect at startup ] Select this option (only once, and hit the Apply button) and the next time that you go online with the Controller, the driver will try to connect to the laser unit immediately. [ View Log File ] This will open the daily laser log file using the standard Windows text editor, e.g. Notepad. More information about the laser log file can be found in the Additional Info pane of this document under section Troubleshooting. [ Open Log File folder ] This will open the current project's LogFiles folder using Windows Explorer. This folder contains the daily laser log file. More information about the laser log file can be found in the Additional Info pane of this document under section Troubleshooting. Further note that the driver will automatically disconnect when going offline, so there is no need to do that manually, although you may do so.
Scanner Mounting	This is a very important setting and it informs the driver how the scanner is physically mounted on the vehicle, with respect to its heading. This setting is used i.c.w. the mounting alignment corrections (roll, pitch and heading offset) from your database system setup.  It means that when the selected scanner mounting is correct, your alignment corrections will be around zero. Normal Select this when the scanner is mounted horizontally (flat on the table), with the cable pointing backwards. Backward Tilted, Cable Down Select this when your scanner is 'looking' backwards (opposite to the vehicle moving direction), with the cable pointing downwards. Forward Tilted, Cable Down Select this when your scanner is mounted on the front side of your vehicle, 'looking' forward in the vehicle's moving direction, with the cable pointing downwards. Upside Down, Cable Backward Select this when your scanner is mounted underneath your vehicle (e.g. UAV or drone), with the cable pointing backwards. More mounting scenarios are predefined and may be selected. Please contact QPS in case your setup is not listed. Note for NORBIT iLiDAR users The integrated scanner inside the Norbit iLiDAR turnkey solution has its 'Cable Down'. Scenario 1 Scenario 2 Topside of the iLiDAR scanner points towards the sailing direction Topside of the iLiDAR scanner points backwards of the sailing direction Use 'Forward Tilted, Cable Down' Use 'Backward Tilted, Cable Down'
Scan Interval	Set to 1 to accept all scans. In this case the horizontal angle between two consecutive scans will be 0.16° To use every n-th scan only, set the interval greater than 1. Note that excluded data due to this setting will not be recorded!
Use Calibration Factors	The calibration correction xml file, VLP16_db.xml, is unique for each unit and contains for every 16 lasers the factory calibrated vertical angle. Yes Select Yes in order to use the calibrated vertical angles from file VLP16_db.xml, instead of the default vertical angles. This xml file must be located in the Qinsy program folder, subfolder XML. Notice that you can not continue with scanning when this file is missing and you selected Yes. No Select No if you do not want to use the calibrated vertical angles, or if the VLP16_db.xml is missing. The default vertical angles will be used for each of the 16 lasers (-15°, -13°, -11°, -9°, -7°, -5°, -3°, -1°, +1°, +3°, +5°, +7°, +9°, +11°, +13°, +15°) Most sensors will be shipped with just the default angles inside the xml file so in this case it doesn't matter to use it or not. Note that data can not be corrected afterwards, in case no or wrong calibration angles were used.
Vertical Area Selection	Physical scan area comprises 16 lasers and yields vertical 30 degrees (in case the scanner is mounted normally on a horizontal surface) For example, laser 1 is looking downwards with an angle of -15°, laser 9 (the nadir) is looking forward (0°) and laser 16 is looking upwards with an angle of +15° Selection here will most likely depend on how you are using the scanner, statically or dynamically: Static scanning is when you put the scanner on a non-moving platform. In that case you want to use all or a part of the 16 available lasers, while the unit is rotating a full circle. Dynamic scanning is when you use the scanner on a moving platform (vessel, car). Then it is recommended to use only one beam, e.g. the nadir one. Most likely you have then physically mounted the scanner with a roll or pitch angle of 90°. Note not to forget to enter the correct C-O offset values in your template setup (see Multibeam Echosounder Parameters). Center (Nadir beam) Typical selection for Dynamic scanning: Only data from laser 9 (with vertical angle of 1°) will be used. Narrow Center (4 beams) Only data from laser 7, 8, 9 and 10 will be used. This covers a vertical area of 6°, looking in the forward direction. Wide Center (6 beams) Only data from laser 6, 7, 8, 9, 10 and 11 will be used. This covers a vertical area of 10°, looking in the forward direction. Above Center (8 beams) Typical selection for Static scanning: Only data from laser 9 - 16 will be used. Below Center (8 beams) Typical selection for Static scanning: Only data from laser 1 - 8 will be used. Entire Area (All beams) Typical selection for Static scanning: Data from all 16 lasers will be used. Blocked data due to this setting will not be recorded!
Horizontal Area Selection	A full circle scan goes from 0 to 360 degrees, with an angle step of 0.16°. 0 degrees means forward, 90 degrees means right (starboard side), 180 degrees looking backward, which is the cable direction, 270 means left (port side). Full Circle Forward / Above Horizon (-90 - +90 deg) Narrow Forward (-45 - +45 deg) Backward / Below Horizon (+90 - +270 deg) Narrow Backward (+135 - +225 deg) Starboard (0 - 180 deg) Port (180 - 360 deg) The Horizontal Area selection will be corrected for the selected Scanner Mounting. I.e. that when you have selected the correct scanner mounting, then Starboard will be starboard, Port will be port, etc. Note that blocked data due to this setting will not be recorded!
Minimum Range	Set the minimum required range in meters. Valid values: 1 to 100 meters. A value of less than 1 meter is possible, and the scanner may return data within this distance, but the manufacturer does not recommend to use ranges less than 1 meter. Using this setting is recommended, but be careful: Blocked data due to this setting (i.e. all returns less than or equal to this range) will not be recorded!
Maximum Range	Set the maximum allowed range in meters. Valid values: 1 to 100 meters. Using this setting is recommended, but be careful: Blocked data due to this setting (i.e. all returns larger than this range) will not be recorded!
Minimum Intensity	Set the minimum required intensity (signal strength). Valid values: 0 to 255. The default minimum intensity is 2, which under normal circumstances only affects the blocking of unwanted 'ghost' returns. Note that blocked data due to this setting (i.e. all returns lower than this intensity) will not be recorded!
Maximum Intensity	Set the maximum allowed intensity (signal strength). Valid values: 0 to 255. Diffuse reflectors (natural objects) will show return values between 0 and 100, retro-reflectors (street signs, lane markers, etc) will return values between 101 and 255. 'Ghost' returns will normally have a value of 0 or 1. Note that blocked data due to this setting (i.e. all returns higher than this intensity) will not be recorded!
Store Laser Location	If enabled, an additional pixel with zero range will be added to each line scan, in order to indicate the exact laser scanner location in the resulting point cloud. This extra pixel will always have beam number 0, and its intensity and quality values will be zero.
Use PPS	This setting is highly recommended, in order to use exact time stamping of the laser data. When enabled, the laser unit must receive a valid PPS/Time Synchronization pulse from an external GNSS receiver and UTC time-tag message. See Timing for more information. Note that this option is disabled while connected, so change setting Connected first from Yes to No in order to change it.
Latency	Enter a fixed latency value in milliseconds. When PPS/Time Synchronization is not used, time stamping of the data is done when the data packet is received at the UDP port. The time will be corrected by subtracting this value. A latency can be provided by the manufacturer, or you may establish a value using a latency calibration procedure. This option is only available when PPS is not used for timing.
Session Setup Format Specifier	This format specifier can be used in combination with the Controller Session Storage Format Specifier #E. The following specifiers are supported (plus your own free text): #N: Name of the system (as defined in the template database setup) #M: Scanner Mounting #C: Use Calibration Factors #S: Scan Interval #V: Vertical Area Selection #H: Horizontal Area Selection #G: Range limits #I: Intensity limits #P: Use PPS The format specifiers are case-sensitive. If you use lower-case then only a value or index number will be displayed. So if you use #E in the Session Storage Setup the filename of the newly recorded database will automatically contain the scanner settings that you were using.
Capture Raw Data	Enable this option if you want to store the raw binary data stream coming straight from the unit to a log file on disk. This may be useful for debugging purposes, or to load the data into other software. This binary log file will be located in the current project's LogFile folder and the naming convention will be <System Name> - DD-MM-YYYY - <Sequence>.bin. The sequence number is incremented after every Start/Stop capturing action. Please note that this binary file is of no use for Qinsy, and it may affect the online performance because of the extra hard disk activity. This option may not be available in your setup. In that case no raw data will be captured.

Generic Display

The Generic Display can be used to validate the laser data integrity. It shows the numerical values for the number of beams (pixels) being scanned per ping (scan), the number of beams being scanned per second, the ping rate (scan rate in Hz), range values, etc.

Important value to monitor is the Ping Age , especially when setting 'Use PPS' is enabled. The Ping Age is the difference between the current computer time and the time of the last received data package. This value should be small, around zero!
Notice that a GPS/PPS may be connected via the interface box to the laser unit, but there is no feedback whether the unit has accepted pulse and/or time-tag.
For example, if you see a very high Ping Age value (+ve or -ve), then this is a severe indication that the initial timing inside the laser unit is wrong.

The Beam Quality value contains the actual beam number (1 - 16), so it has nothing to do with any quality or intensity value.

The Status Flag value indicates whether you are using the calibrated vertical angles from the external angular correction xml file or not and whether PPS/Time Synchronization is used or not.

You may use the attached example  Generic Display Layout file as an example: Copy this layout (Use 'Save Link As...') to your current Project's Settings\Display folder and open it using a new Generic Display.
You only have to select the correct laser system as defined in your template setup (Select Edit, Layout…, go to RAW DATA, Multibeam Echosounder (2), and select your laser system for both parent items).

Raw Multibeam Display

Open View Properties and set the Backscatter Intensity range between 0 and 255.

Enable Waterfall scrolling, and set both scroll values to 0 (zero) pixels.

If you want to see the intensity while online, open View Properties and set the Color Coding to Backscatter.

Additional Information

 The VLP-16 has the following features and limitations:

• The vertical angle resolution between each of the 16 lasers is 2.0° and this means a vertical field of view of 30° is available.
• The horizontal angle resolution goes from 0.1° to 0.4°.
• Spin rate of the unit can be 5 Hz (300 RPM) to 20 Hz (1200 RPM).
• Maximum deliverable of approximately 300 thousand measurements / second.
• Minimum range 1 meter. You may receive returns from objects closer by, but the manufacturer recommends not to use these.
• Maximum range 100 meters. You may receive returns from further away than 100 meters, but the manufacturer recommends not to use these.
• The decoded intensity will be a value between 0 and 255 and depends on the target's surface being hit.
  The intensity will be the calibrated reflectivity: Diffuse reflectors (natural objects) will show values between 0 and 100 (for 0% - 100% reflectivity) and retro-reflectors (street signs, lane markers, license plates, etc) will show values between 101 and 255.
  'Ghost' returns will normally have a value of 0 or 1.

Due to the UDP broadcast characteristic of the Velodyne a ping (or full scan) does not contain all the beams from one full rotation. A ping in Qinsy will be filled with all laser firing data received from ten consecutive UDP packets.
One packet contains 12 times data for all 16 lasers (with a horizontal increment of 0.16°), so a Qinsy ping contains a maximum of 3840 beams.
Note that the beam quality value is 'mis-used' in order to store the real beam number (1 - 16). You may color-code on 'quality' in the Validator for an indication of which beams have been used.

No Data

You have made a successful network connection with Qinsy but no laser data is coming in.

You open the scanner's IP address with a web browser and you'll see normal web interface: the GPS Position field and PPS may be updated, but with Qinsy online no laser data is coming in.

You open a sensors stream with VeloView (Velodyne's own software) but no laser data is visible.

This all may well be caused by the scanner being powered with a too low voltage, in that case: please check the power of the scanner!

Important Information

It is important to prepare the project prior to the start of the scanning by optimizing all parameters to meet the necessary requirements:
Select the right Vertical and/or Horizontal Area selection and/or range blocking in order to decrease the number of expected points per second.