Class CVelodyneScanner

Defined in File CVelodyneScanner.h

Nested Relationships

Nested Types

Inheritance Relationships

Base Type

public mrpt::hwdrivers::CGenericSensor (Class CGenericSensor)

Class Documentation

class CVelodyneScanner : public mrpt::hwdrivers::CGenericSensor 

A C++ interface to Velodyne laser scanners (HDL-64, HDL-32, VLP-16), working on Linux and Windows. (Using this class requires WinPCap as a run-time dependency in Windows). It can receive data from real devices via an Ethernet connection or parse a WireShark PCAP file for offline processing. The choice of online vs. offline operation is taken upon calling initialize(): if a PCAP input file has been defined, offline operation takes place and network is not listened for incoming packets.

Parsing dual return scans requires a VLP-16 with firmware version 3.0.23 or newer. While converting the scan into a point cloud in mrpt::obs::CObservationVelodyneScan you can select whether to keep the strongest, the last or both laser returns.

XML calibration files are not mandatory for VLP-16 and HDL-32, but they are for HDL-64.

Grabbing live data (as a user)

Use the application velodyne-view to visualize the LIDAR output in real-time (optionally saving to a PCAP file) or to playback a PCAP file.
Use rawlog-grabber to record a dataset in MRPT’s format together with any other set of sensors. See example config file: MRPT\share\mrpt\config_files\rawlog-grabber\velodyne.ini

Grabbing live data (programmatically)

See CGenericSensor for a general overview of the sequence of methods to be called: loadConfig(), initialize(), doProcess().
Or use this class inside the application rawlog-grabber. See example config files: MRPT\share\mrpt\config_files\rawlog-grabber\velodyne.ini

See the source code of the example application [MRPT]/apps/velodyne-view (velodyne-view web page) for more details.

Playing back a PCAP file:

It is common to save Velodyne datasets as Wireshark’s PCAP files. These files can be played back with tools like bittwist, which emit all UDP packets in the PCAP log. Then, use this class to receive the packets as if they come from the real sensor.

Alternatively, if MRPT is linked against libpcap, this class can directly parse a PCAP file to simulate reading from a device offline. See method setPCAPInputFile() and config file parameter ``

To compile with PCAP support: In Debian/Ubuntu, install libpcap-dev. In Windows, install WinPCap developer packages + the regular WinPCap driver.

Configuration and usage:

Data is returned as observations of type:

mrpt::obs::CObservationVelodyneScan for one or more “data packets” (refer to Velodyne usage manual)
mrpt::obs::CObservationGPS for GPS (GPRMC) packets, if available via the synchronization interface of the device. See those classes for documentation on their fields.

Configuration includes setting the device IP (optional) and sensor model (mandatory only if a calibration file is not provided). These parameters can be set programmatically (see methods of this class), or via a configuration file with CGenericSensor::loadConfig() (see example config file section below).

About timestamps:

Each gathered observation of type mrpt::obs::CObservationVelodyneScan is populated with two timestamps, one for the local PC timestamp and, if available, another one for the GPS-stamped timestamp. Refer to the observation docs for details.

Format of parameters for loading from a .ini file

 PARAMETERS IN THE ".INI"-LIKE CONFIGURATION STRINGS:
-------------------------------------------------------
  [supplied_section_name]
  # ---- Sensor description ----
  #calibration_file         = PUT_HERE_FULL_PATH_TO_CALIB_FILE.xml      //
Optional but recommended: put here your vendor-provided calibration file
  model                    = VLP16      // Can be any of: `VLP16`, `HDL32`,
`HDL64`  (It is used to load default calibration file. Parameter not required
if `calibration_file` is provided.
  #pos_packets_min_period  = 0.5        // (Default=0.5 seconds) Minimum
period to leave between reporting position packets. Used to decimate the
large number of packets of this type.
  # How long to wait, after loss of GPS signal, to report timestamps as "not
based on satellite time". 30 secs, with typical velodyne clock drifts, means
a ~1.7 ms typical drift.
  #pos_packets_timing_timeout = 30      // (Default=30 seconds)
  # ---- Online operation ----

  # IP address of the device. UDP packets from other IPs will be ignored.
Leave commented or blank
  # if only one scanner is present (no IP filtering)
  #device_ip       = XXX.XXX.XXX.XXX

  #rpm             = 600        // Sensor RPM (Default: unchanged). Requires
setting `device_ip`
  #return_type     = STRONGEST  // Any of: 'STRONGEST', 'LAST', 'DUAL'
(Default: unchanged). Requires setting `device_ip`

  # ---- Offline operation ----
  # If uncommented, this class will read from the PCAP instead of connecting
and listeling
  # for online network packets.
  # pcap_input     = PUT_FULL_PATH_TO_PCAP_LOG_FILE.pcap
  # pcap_read_once = false   // Do not loop
  # pcap_read_fast = false    // fast forward skipping non-velodyne packets
  # pcap_read_full_scan_delay_ms = 100 // Used to simulate a reasonable
number of full scans / second
  # pcap_repeat_delay = 0.0   // seconds

  # ---- Save to PCAP file ----
  # If uncommented, a PCAP file named
`[pcap_output_prefix]_[DATE_TIME].pcap` will be
  # written simultaneously to the normal operation of this class.
  # pcap_output     = velodyne_log

  # 3D position of the sensor on the vehicle:
  pose_x     = 0    // 3D position (meters)
  pose_y     = 0
  pose_z     = 0
  pose_yaw   = 0    // 3D orientation (degrees)
  pose_pitch = 0
  pose_roll  = 0

Copyright notice

Portions of this class are based on code from velodyne ROS node in https://github.com/ros-drivers/velodyne Copyright (C) 2007 Austin Robot Technology, Patrick Beeson Copyright (C) 2009, 2010 Austin Robot Technology, Jack O’Quin License: Modified BSD Software License Agreement

Note

New in MRPT 1.4.0

Change configuration parameters; to be called BEFORE initialize();

see above for the list of parameters and their meaning

inline void setModelName(const model_t model): See supported model names in the general discussion docs for mrpt::hwdrivers::CVelodyneScanner

inline model_t getModelName() const

inline void setPosPacketsMinPeriod(double period_seconds): Set the minimum period between the generation of mrpt::obs::CObservationGPS observations from Velodyne Position RMC GPS packets

inline double getPosPacketsMinPeriod() const

inline void setPosPacketsTimingTimeout(double timeout): Set how long to wait, after loss of GPS signal, to report timestamps as “not based on satellite time”. 30 secs, with typical velodyne clock drifts, means a ~1.7 ms typical drift.

inline double getPosPacketsTimingTimeout() const

inline void setDeviceIP(const std::string &ip): UDP packets from other IPs will be ignored. Default: empty string, means do not filter by IP

inline const std::string &getDeviceIP() const

inline void setPCAPVerbosity(const bool verbose): Enables/disables PCAP info messages to console (default: true)

inline void setPCAPInputFile(const std::string &pcap_file): Enables reading from a PCAP file instead of live UDP packet listening

inline const std::string &getPCAPInputFile() const

inline void setPCAPOutputFile(const std::string &out_pcap_file): Enables dumping to a PCAP file in parallel to returning regular MRPT objects. Default=””: no pcap log.

inline const std::string &getPCAPOutputFile() const

inline void setPCAPInputFileReadOnce(bool read_once)

inline bool getPCAPInputFileReadOnce() const

inline const mrpt::obs::VelodyneCalibration &getCalibration() const

inline void setCalibration(const mrpt::obs::VelodyneCalibration &calib)

bool loadCalibrationFile(const std::string &velodyne_xml_calib_file_path)

Returns false on error.