Laser Scanning - RIEGL VQ-250 (UTC) - 20

Description

Driver to decode data from RIEGL VQ-250 laser scanners.

VQ-250

VMX-250

Ultra-high speed “full circle” laser scanner,
ideal for mobile mapping applications

1.5m - 500m

Two VQ-250 scanners,
combined and integrated with
GNSS and INS on one platform.

Laser stands for Light Amplification by Stimulated Emission of Radiation.

All RIEGL VQ laser scanners are eye-safe, using laser class 1R (IEC 60825-1). Characteristic of class 1R laser is that you will not receive any reflection from a water surface, which makes this scanner ideal for combining with multibeam data acquisition surveys.

It is highly recommended to interface the VQ scanner with a Time Synchronization pulse, in order to time-tag all data with UTC. Actually, this interfacing requirement is mandatory when using the scanner on a moving platform.

The so-called PPS pulse should comes from an external GNSS receiver. See paragraph 'Interfacing' below for more details.

Support

Please contact QPS if you need support for the RIEGL VQ-180 or VQ-450 scanner types which are not described in this document.

Driver Information

Driver	RIEGL VQ-250 (Network) (XML)	Interface Type	Freebase/TCP/IP/UDP	Driver Class Type	Freebase
UTC Driver	Yes	Input / Output	Input/Output	Executable	DrvLaser.exe RIEGL_VQ250
Related Systems	Page: Laser Scanning - RIEGL VQ-250 (UTC) - 20 — Multibeam Echosounder Page: Laser Scanning - RIEGL VQ-250 - 20 — Multibeam Echosounder
Related Pages	Laser Scanning - RIEGL VZ 400/1000/2000/4000/6000 Laser Scanning - RIEGL VZ-400i

Decoding Notes

Data is always broadcast via a TCP network. It is advisable to use a fast (gigabit) network card, due to real-time scanning.

The actual raw binary datastream is in so-called RXP format, a proprietary data format defined by RIEGL. This document does not describe the RXP format.

The driver is configured as a multibeam system and creates XYZ 'multibeam' observations.

('multibeam' versus 'laser scanning'-terminology: ping = scan (i.e. 360° around), footprint = pixel = pulse, swath = line)

The number of beams (pixels) depends on the on-line used settings, like (user-definable) range mask, vertical angle mask, intensity mask, etc. (see Controller Setup below).
The maximum expected number of beams per second is 300000 (300KHz).
The maximum theoretical number of beams per scan is about 20000. Under normal conditions you will expect values of 2000 to 5000 pixels.
The number of scans (lines) per second depends also on the combination of user-definable settings, the maximum will be 100 Hz.

Next to the pixel XYZ value, three other important attributes are stored, dealing with the reflection from the target's surface:

Echo return type
The echo return type indicates whether the returned signal is a single, a first, an interior or a last echo from the same emitted pulse.
This means that one pulse may return multiple beams (pixels), e.g. the first return from a tree-leaf, an interior return type from another leaf, and a last return type from a wall.
Amplitude
The value of the pixel amplitude (returned power) is situation dependent, and its range will be between 0 and 80 dB.
Reflection
More important and more usable is the reflectance, a kind of 'normalized' amplitude. This will always be in the range of -25 dB to 65 dB.
It is the received power relative to the power that would be received from a white diffuse target (0 dB) at the same distance. The surface normal of this target is assumed to be parallel to the laser beam direction.

Qinsy will store these attributes as follows:

The amplitude is stored as Quality.
If setting 'Modify Intensity Echo types' is enabled (see Online Setup below), it will be 255 in case of a last echo return type, and 0 (zero) in case of an interior echo return type. For first and single echo types it will be the exact value as reported by the scanner.

The reflection is stored as Intensity.
If setting 'Modify Intensity Echo types' is enabled (see Online Setup below), it will be the reflectance plus 1000 in case of a last echo return type, and reflectance minus 1000 in case of an interior echo return type. For first and single echo types it will be the exact value as reported by the scanner.

The Quality or Intensity value can be used for color-coding, e.g. when viewing the final point cloud in the Validator.

Interfacing Notes

By default, the driver will time-stamp the data when received at the UDP port. However, due to network characteristics in general, this may result in inaccurate timing. Therefore timing via PPS pulse from GPS is highly recommended.

When the PPS pulse and the Timetag message are fed into the GPS Sync connector, then the LED should be green when all is okay. When the LED is not green (e.g. orange), then no data will be outputted:

PPS Okay (Green LED) PPS Not Okay (Orange LED)

Database Setup

Add a Multibeam Echosounder system to your template setup, and select driver "Laser Scanning - RIEGL VQ-250 (Network) (XML) (With UTC)".

The Port number must be the same as the configuration port of the scanner, normally 20002. The driver will communicate (sending and receiving commands) via this configuration port of the scanner. The real-time line-stream is received via the data port, and should always be the configuration port minus one, so normally 20001.

Important is to enter for the IP Address the address of the scanner, by default this is 192.168.0.127 or 192.168.0.128.
It is recommended to have a dedicated network interface between your computer and the scanner. However, in case your computer's network card subnet IP address differs from the scanner's IP address, and you can not change the address of your computer's network card (e.g. other network devices are also connected), it is possible to change the default IP address of the scanner. Please consult the laser scanner manual, or contact RIEGL support on how to do this.

The maximum update rate is not used, so leave it at zero.
On the next page, the Transducer Location and Mounting Angles are important.

The exact values for the roll, pitch and heading offsets should be established after a calibration procedure. Before such a calibration one should use values that are as accurate as possible:
E.g when the rotating mirror of the scanner is pointing forward on your survey object, you could already enter 180° for the heading offset. Pointing backwards means a heading offset of 0°.
Leave the roll offset to 0° if the mounting plate of the scanner is pointing downwards.

If the scanner is part of a VMX-250 car installation, you could already enter the following 'installation' offset angles:
For the left scanner use Roll: -90°, Pitch: -36° and Heading: +30°.
For the right scanner use Roll: +90°, Pitch: -36° and Heading: -30°.

Set the Max. beams per Ping value to 40000. The actual number of beams will be variable, and depends for example on the on-line used settings, and on the targets being scanned.
Leave all other values on the next page(s) also at their default values.

Online

When on-line, the laser unit can be controlled using the Controller:

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

First of all, a (TCP/IP) network connection has to be established between Qinsy and the laser unit. This has to be done every time you go on-line:

Change in the 'Control' tab page option 'Connected' to Yes and select the Apply button. Wait until you see in the Events list that a connection has been made successfully.

Connected

Connect (using TCP/IP) to the so-called LRC Server of the Laser Scanner. Make sure that the IP address entered in Database Setup is correct. Under normal circumstances a successful connection will be established within a second. If it takes considerable more time, you should check your network cable/configurations.
If no network connection can be made at all, e.g. the laser unit is switched off, then it may take 5 to 10 seconds before you will be informed.
You may also use the Ping command from the Windows Command Prompt in order to check a successful network connection between Qinsy and the scanner:

Action

Selected action will be send to the laser unit, immediately after hitting the Apply or OK button. You must be connected first in order to select an action.

Notice that any selection will always revert back to [ None ], after each selected action.

First time users should read the comments under Important Information below.

It is recommended to wait a few moments after each action, until the status in the Events list is updated with a message, because it takes some time for the unit to handle each command (action).

[ None ]
This will be the selection after each action. Nothing will happen when hitting the Apply or OK button.
Start
Select this action in order to start scanning. Notice that it may take a few seconds before the first data is received, so be patient for at least 5 seconds.
Stop
Select this action in order to stop scanning. Scanning will be stopped immediately, after hitting the Apply or OK button. The laser will also stop scanning automatically when going offline with the Controller.
[ REBOOT ]
Useful action for units with no selection panel or power/reset button on the unit itself, like the VQ-250.
Select this action to reboot the laser unit, which is comparable to the sequence of a shutdown followed by a power up. Please notice that it takes several minutes before the unit is up and running, prior to re-connecting.
[ SHUTDOWN ]
Useful action for units with no selection panel or power/reset button on the unit itself, like the VQ-250.
This action is highly recommended in order to take the power of the unit first, because you should not simply unplug the power cables from the unit.

Vertical Area Selection

Scanner head rotates 360° every line at high speed. 0° (phi) means looking down, 180° means looking up, 90° looking right, 270° looking left.

Notice that the scanner's own XYZ co-ordinate system differs from the Qinsy XYZ system:

Qinsy	VQ-250
X	+Y
Y	0
Z	+X

Select the required scheme from the list. Schemes are defined in the Laser Device Settings XML File.

Excluded data due to this setting will not be recorded.

Sector Reduction

Select the required scheme from the list. Schemes are defined in the Laser Device Settings XML File.
Excluded data due to this setting will not be recorded.

Scan Rate

Select the required scanner measurement rate, i.e. number of pixels / second.
Notice that some combinations with Scan Resolution may not be possible. In that case you will be informed in the Event List after hitting the Apply button.

Scan Resolution

Select the required vertical angle resolution, i.e. the angle increment between two consecutive pixels.
Notice that some combinations with Scan Speed may not be possible. In that case you will be informed in the Events List after hitting the Apply button

Minimum Range

Set the minimum required range in meters. Valid Values: 1.5 to 500 meters.

Using this setting is recommended, but be careful: Blocked data d/t this setting (i.e. all pixels less than this range) will not be recorded!

Maximum Range

Set the maximum allowed range in meters. Valid Values: 1.5 to 500 meters.

Using this setting is recommended, but be careful: Blocked data due to this setting (i.e. all pixels more than this range) will not be recorded!

Minimum Amplitude

Set the minimum required amplitude (returned power in dB) value.

Values are scanner dependent, and normally in the range between 0 - 80 dB.

Notice that blocked data due to this setting will not be recorded.

This option may not be available in your setup. In that case all amplitude values will be accepted.

Maximum Amplitude

Set the maximum allowed amplitude (in dB) value.

Values are scanner dependent, and normally in the range between 0 - 80 dB.

Notice that blocked data due to this setting will not be recorded.

This option may not be available in your setup. In that case all amplitude values will be accepted.

Minimum Reflection

Set the minimum required reflection (in dB). The reflection is a 'normalized' amplitude, and values are in the range between -25 dB to 65 dB.

It is the received power relative to the power that would be received from a white diffuse target (0 dB) at the same distance. The surface normal of this target is assumed to be parallel to the laser beam direction.

Notice that blocked data due to this setting will not be recorded.

This option may not be available in your setup. In that case all reflection values will be accepted.

Maximum Reflection

Set the maximum allowed reflection (in dB). The reflection is a 'normalized' amplitude, and values are in the range between -25 dB to 65 dB.

It is the received power relative to the power that would be received from a white diffuse target (0 dB) at the same distance. The surface normal of this target is assumed to be in parallel to the laser beam direction.

Notice that blocked data due to this setting will not be recorded.

This option may not be available in your setup. In that case all reflection values will be accepted.

Atmospheric Relative Humidity

Set the current atmospheric relative humidity. Valid values: 0% - 100%.

Atmospheric parameters are needed when highly accurate range measurements are required.

This option may not be available in your setup. In that case the default value will be used.

AtmosphericTemperature

Set the current atmospheric temperature in degrees Celsius. Valid values: -50°C - 100°C.

Atmospheric parameters are needed when highly accurate range measurements are required.

This option may not be available in your setup. In that case the default value will be used.

Atmospheric Pressure at Sealevel

Set the atmospheric pressure at sealevel in mbar. Valid values: 0 - 1200 mbar.

Atmospheric parameters are needed when highly accurate range measurements are required.

This option may not be available in your setup. In that case the default value will be used.

Height above Mean Sealevel

Set the height above mean sealevel in meters. Valid values: 0 m - 1000 m.

Atmospheric parameters are needed when highly accurate range measurements are required.

This option may not be available in your setup. In that case the default value will be used.

Multi Target Measurement

One emitted laser pulse may hit one or several targets, causing one or several echo pulses.

For example the first return is from a tree-leaf, an interior return type comes from another leaf, and a possible last return type because of hitting the wall. Select here the type of echo pulse you want to decode.

Notice that blocked data due to this setting will not be recorded.

Modify Intensity Echo types

When enabled, the original reported intensity and quality value for interior and last echo types will be modified. Notice that the value for first and single echo types are never modified.
See also the detailed explanation under Decoding Notes.

Store Laser Location

If enabled, an additional pixel with zero co-ordinates 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 1, and its intensity/quality value will be zero.

Use PPS

Notice that this setting is only available when laser driver '...(With UTC)' has been selected in your template setup.
When enabled, the scanner needs a valid NMEA GGA message and PPS pulse from an external GPS receiver.
The exact I/O parameters from this external GPS need to be defined using the following settings below.

PPS Trigger Edge

Select the used trigger edge of the external GPS PPS pulse. It depends on the external GPS receiver being used and you should therefore consult the GPS manual.

This setting is only available when using PPS from an External GPS.

GPS Baudrate

Select the baud rate of the external GPS receiver connected to the scanner.

The GPS Sync led on the laser will only turn green when this GPS Baudrate and the GPS Format (below) settings are correct!

This setting is only available when using PPS from an External GPS.

GPS Format

Select the format of the external GPS message connected to the scanner:

The GPS Sync led on the laser will only be green when this GPS Format and the GPS Baudrate (above) settings are correct!

This setting is only available when using PPS from an External GPS.

NMEA GGA
Notice that NMEA ZDA is only supported by scanners which have the latest firmware installed.
IGI ($TOPAL)
For this format it is important to set the correct 'UTC to GPS Correction' (leap-second) in your template setup (as of July 1, 2012, this value is 16 sec).
NMEA ZDA
This format is only supported by scanners updated with the latest firmware.
Please contact RIEGL in order to verify if your scanner has the latest firmware.

PPS Pulse/Data Sequence

Select if the external PPS pulse comes before the GPS data string, or vice versa.

This setting is only available when using PPS from an External GPS.

Additional Information

First time users may experience that action Start will start the scanner, but no data is received in Qinsy, and perhaps that the scanner can't be stopped using the Stop action command.

Therefore please use the following procedure when:
– you are using the scanner for the first time, e.g with factory default settings.
– you have used the scanner successfully without PPS (Time Synchronization) timing and now you want to use it with PPS timing.
– you have used the scanner successfully with PPS (Time Synchronization) timing and now you want to use it without PPS timing.

When not using PPS timing:
Go on-line with Qinsy, using the "Laser Scanning - RIEGL VQ-250 (XML)"-driver and make a successful connection with the scanner. Change one of the settings and press the Apply button. Do not use the Start action command! Go off-line with Qinsy and then on-line again. Now you may use action Start in order to continue with your survey.

When using PPS timing:
Go on-line with Qinsy, using the "Laser Scanning - RIEGL VQ-250 (XML) (With UTC)"-driver and make a successful connection with the scanner. Set the correct GPS Baudrate and GPS Format and press the Apply button. Do not use the Start action command!
Make sure that the green GPS Sync LED is burning. If so, go off-line with Qinsy, and go on-line again. Now you may use action Start in order to continue with your survey.

When you can't stop the scanner while scanning (i.e. head is rotating) using the Stop action command, go off-line with Qinsy (this may take a longer time than usual), go on-line again and re-connect to the scanner. The scanner will then immediately stop scanning, and you may continue with your normal activities.

Problems

If you experience problems using your laser scanner in combination with this driver, or if you need additional information or support, please attach the daily laser log-file when submitting your JIRA support ticket.

The most commonly reported problem is that network data is blocked by the Windows Firewall. When this happens you may see that data does come in using other utilities (like the IO Tester or the manufacturer's own software), but that the Qinsy driver does not accept any data.

The following (Windows 7) steps may solve this:

Go offline, open the Control Panel (Start menu, Settings, Control Panel)
Select Windows Firewall (System and Security)
Select Advanced Settings (Upper left corner)
Select Inbound Rules, highlight all 'Driver for Laser Scanning' entries and delete them using the right mouse popup menu (or Del key)
If you now go online, the Windows Security Alert message will pop up: It is important to check all three check boxes!

Another possible problem could be that your computer has more than one network cards installed (e.g. LAN and WIFI), but within the same sub-net mask range (255.255.255.0). It is recommended to make the first three digits unique for each network card IP address.
You may check the daily laser log-file, it will show the IP addresses for all available network adapters and indicates which one the driver will use.

Please check that the driver is using the correct one.

Daily Laser Log File

All user actions are logged in a daily laser log file. You will find this file in the current project's LogFiles folder.
The filename convention for this ASCII log-file is <System Name> DD-MM-YYYY.log.

Notice that all time stamps in this log file are by default in UTC.
An advanced user may change this to local time zone (LTZ) by changing the registry key:

HKEY_CURRENT_USER\Software\QPS\QINSy\8.1\Drivers\DrvLaser\Settings\TimeLogFileUtc value from 1 to 0.

Improve Performance

Due to the enormous amount of data to be expected while scanning and recording, it is recommended to keep the system overhead as low as possible.

Here you'll find some tips and tricks in order to fine-tune your setup.

However, these are not strict rules, because each project is different and depends on the current situation and hardware being used. Your goal should be to keep your system CPU usage as low as possible.

HARDWARE
Virus Scanner	Disable Virus Scanner, or at least the setting 'Scan Files when Writing/Reading to/from disk'.
Storage	Make use of Solid State Drive (SSD), or fast SATA hard drive (7200 - 10000 rpm).
Network	Your network card speed should never be lower than the scanner's network speed. Use a network card that can be configured for 100Mbit or 1Gbit speed. Do not use USB Networking Adapters, because this may result in loss of data when huge amounts of data are being broadcast.
Task Manager CPU	General Task Manager CPU Usage should be less than 50%. CPU load of each display must be less than 10-15%. Make sure that the 'Working Set (Memory)' column for process Multibeamer.exe and/or DrvResultOut.exe is not constantly increasing, especially during recording.
PROJECT PREPARATION
Laser Device Settings	During project preparation, establish the optimum settings in order to achieve the required results. The most benefit you will gain from setting the Scan Speed, Scan Rate, Scan Resolution, Angle Resolution, Vertical Area Selection, Scan Area Selection and Sector Reduction as well as possible. Especially the Vertical or Scan Area Selection is very important. Make use of Mask schemes to define areas which you don't want to scan.
ONLINE
Raw Multibeam Display	Open only one Raw Multibeam Display. Disable the options 'Show Big Dots' and 'Draw Lines'.
Navigation Display	Open only one Navigation Display. Preferably disable DXF and TIFF layers. These layers should only be used during project preparation. When 'object tracking' is enabled, do not zoom in too close. Keep in mind that the display should not be 'refreshed' more than 1x per second.
3D Point Cloud Display	It is not recommended to use a 3D Point Cloud Display. If you do so, make sure your hardware contains a high-spec video card.
- Sounding Grid - Dynamic Surface	Storage to a Sounding Grid is not recommended, and should be purely for display purposes: e.g. for checking the scan coverage or for showing the 95% Confidence Level statistics. If you do want to see the scan coverage then it is advisable to store to a sounding grid and not to the dynamic surface Do not use a small cell-size, preferably not less than 1.0 meter. If you notice in the Navigation Display that the real-time sounding grid is drawn/updated with a delay, then please increase the cell-size or disable the storage completely. Offline (Replay) there are no limitations and you may use small cell-sizes, e.g. 0.10 meter.
OFFLINE
Replay	In Replay there are no limitations as mentioned above: use as many displays as you like, store to sounding grids with small cell-sizes, update the dynamic surface, etc. All this may only affect the replay speed, but the data integrity of your final DTM processing files should be fine.

Controller Computation Setup	While working online, disabling the laser system in your Computation Setup will have the most effect on the performance Footprints will not be geo-referenced, nor corrected for motion, heading or timing in real-time. This will save a tremendous amount of CPU power and memory usage. This tip allows you to get the most out of your scanner: maximum scanning speed and maximum scanning rate, without the risk of losing scans due to performance issues. Drawback is that no DTM file (e.g. QPD) is created, nor a sounding grid is filled, while working online. To create a final DTM and/or Sounding Grid file you need to Replay the recorded databases afterwards.