ROS package to parse NMEA GPS and Depth sentences, obtained from a Lowrance Elite 5-TI side-scanner, into ROS topics. The package currently contains one node, which receives the NMEA sentences via UDP. Four new message types are defined, as there are no standard ROS messages for some of the side-scanner NMEA sentences:

• DepthOfWater.msg: Following the DPT sentence
• DepthBelowTransducer.msg: Following the DBT sentence
• WaterHeadingSpeed.msg: Following the VHW sentence
• MagneticHeading.msg: Following the HDG sentence

Partly based on code from this ROS node.

• nmea_msgs

• Install or resolve dependencies (see above)
• Clone this repository to your catkin workspace src directory (e.g., $HOME/catkin_ws/src)
• From your catkin workspace root directory (e.g., $HOME/catkin_ws), run the catkin_ws command

You can run the UDP node by running a roscore, and then using the rosrun command:

roscore &
rosrun ros_nmea_depth nmea_depth_udp.py

Alternatively, a ROS launch file is provided, where the default parameters (see below) are set as:

• Frame ID: lowrance
• IP Address: None (UDP multicast)
• UDP Port: 12021

All topics are published relative the device's namespace, referred here by the frame_id parameter, and the sensor where the data is obtained. For example, if running the lowrance launch file, the frame_id will be lowrance, and thus the GPS time reference topic will be /lowrance/gps/time_reference.

• <frame_id>/nmea_sentence (nmea_msgs/Sentence): A message representing a single NMEA0183 sentence

• <frame_id>/gps/fix (sensor_msgs/NavSatFix): GPS Position Fix information (WGS84)

• <frame_id>/gps/vel (geometry_msgs/TwistStamped): GPS reported ground speed (in m/s)

• <frame_id>/gps/time_reference (sensor_msgs/TimeReference): Time reference in GPS time (GPST)

• <frame_id>/gps/active_satellites (nmea_msgs/Gpgsa): GPS Dillution of Position (DOP) and active satellite data

• <frame_id>/gps/satellites_in_view (nmea_msgs/Gpgsv): Information on all GPS satellites currently in view, specifically PRN, elevation angle, azimuth angle and signal-to-noise ratio

• <frame_id>/scanner/magnetic_heading (ros_nmea_depth/MagneticHeading): Magnetic heading for sidescanner sensor, following the HDG NMEA sentence

• <frame_id>/scanner/water/depth (ros_nmea_depth/DepthOfWater): Depth of water column, following the DPT NMEA sentence

• <frame_id>/scanner/water/depth_below_transducer (ros_nmea_depth/DepthBelowTransducer): Depth of water column, following the DBT NMEA sentence

• <frame_id>/scanner/water/heading_and_speed (ros_nmea_depth/WaterHeadingSpeed): Speed and heading (true and magnetic) for the sidescanner sensor relative to the water, following the VHW NMEA sentence

• <frame_id>/scanner/water/temperature (sensor_msgs/Temperature): Mean temperature of water, as measured by the sidescanner sensor (MTW NMEA sentence), in Celsius

• ~address (string, default: None)

IP address for source of NMEA sentences. Default is defined by an environment variable called "SONAR", which must be set before running the launch file:

export SONAR=<your_sonar_ip_address>

• ~port (int, default: 12021)

TCP/UDP port for source of NMEA sentences. Default is a random port, defined by our Lowrance sonar. You must change this parameter to reflect the inbound connection with your device. You can do this either by modifying the ROS launch file or by specifying this parameter when using rosrun. For example, when running the TCP node:

rosrun ros_nmea_depth nmea_depth_tcp.py _port:=<your_port>

• ~frame_id (string, default: None)

Name or ID of device which produces the NMEA sentences (e.g., lowrance).

• ~update_rate (int, default: 40)

Rate of publishing NMEA sentences for TCP and UDP nodes. If your sonar transmits NMEA sentences too fast, the TCP/UDP nodes may miss some sentences, and increasing this parameter may prevent these losses. However, be wary of the node's CPU and bandwidth usage, both which may increase with higher publishing frequencies.

• Renan Maidana: ROS package and UDP node
• Guilherme Heck: Sidescanner (Lowrance SL2) interface, debugging and logging
• Alexandre Amory: Guidance and logistics