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Overview

This package provides a ROS interface for GPS devices that output compatible NMEA sentences. See the GPSD documentation of NMEA sentences for details on the raw format. Of the thousands of NMEA-compatible GPS devices, we are compiling a list of devices known to be supported.

This package is compatible with the geographic_info project as well as any other nodes that support sensor_msgs/NavSatFix and/or sensor_msgs/TimeReference.

No C++ or Python API is provided, only a ROS API.

This package replaces the nmea_gps_driver package present in Fuerte and Groovy.

Sample Usage

To get up and running quickly, you can use the following command to start outputting your GPS data onto ROS topics. This assumes your GPS is outputting GGA NMEA sentences, is connected to /dev/ttyUSB0 and is communicating at 38400 baud.

$ rosrun nmea_navsat_driver nmea_serial_driver _port:=/dev/ttyUSB0 _baud:=38400

Roadmap

• Add support for additional NMEA sentences beyond GSA, RMC and GGA. Specific requests for support of individual sentences should be filed as enhancement tickets.
• Add sentence synchronization. Currently, there is little or no buffering, which prevents the driver from using multiple types of sentences to generate one cycle of topic outputs.

Nodes

nmea_topic_driver

NMEA GPS Topic driver node. Reads NMEA sentences from a ROS topic instead of directly from e.g. a serial port.

Subscribed Topics

nmea_sentence (nmea_msgs/Sentence)

• NMEA sentences, 1 per message. The header.stamp should correspond to the time that the message was read from the device for accurate time_reference output. The header.frame_id on the messages on this topic will be used when setting frame_id on the output messages. These sentences do not have to be checksummed or otherwise validated before reaching the driver.

Published Topics

fix (sensor_msgs/NavSatFix)

• GPS position fix reported by the device. This will be published with whatever positional and status data was available even if the device doesn't have a valid fix. Invalid fields may contain NaNs.

vel (geometry_msgs/TwistStamped)

• Velocity output from the GPS device. Only published when the device outputs valid velocity information. The driver does not calculate the velocity based on only position fixes.

time_reference (sensor_msgs/TimeReference)

• The timestamp from the GPS device is used as the time_ref.

Parameters

~time_ref_source (string, default: <the value of ~frame_id>)

• The value to use as the source in the sensor_msgs/TimeReference.

~useRMC (bool, default: False)

• Whether to generate position fixes from GGA sentences or RMC sentences. If True, fixes will be generated from RMC. If False, fixes will be generated based on the GGA sentences. Using GGA sentences allows for approximated covariance output while RMC provides velocity information.

nmea_serial_driver

NMEA GPS Serial driver node. Replaces nmea_gps_driver.py to reduce naming conflicts and use new common parsing+driver backend.

Published Topics

fix (sensor_msgs/NavSatFix)

• GPS position fix reported by the device. This will be published with whatever positional and status data was available even if the device doesn't have a valid fix. Invalid fields may contain NaNs.

vel (geometry_msgs/TwistStamped)

• Velocity output from the GPS device. Only published when the device outputs valid velocity information. The driver does not calculate the velocity based on only position fixes.

time_reference (sensor_msgs/TimeReference)

• The timestamp from the GPS device is used as the time_ref.

Parameters

~port (string, default: /dev/ttyUSB0)

• The device path

~baud (int, default: 4800)

• The baud rate to receive NMEA data.

~frame_id (string, default: gps)

• The frame_id for the header of the sensor_msgs/NavSatFix and geometry_msgs/TwistStamped output messages. Will be resolved with tf_prefix if defined.

~time_ref_source (string, default: <the value of ~frame_id>)

• The value to use as the source in the sensor_msgs/TimeReference.

~useRMC (bool, default: False)

• Whether to generate position fixes from GGA sentences or RMC sentences. If True, fixes will be generated from RMC. If False, fixes will be generated based on the GGA sentences. Using GGA sentences allows for approximated covariance output while RMC provides velocity information.

nmea_topic_serial_reader

Reads NMEA sentences from the specified serial port and publishes them to a ROS topic. This is a simple front-end for use with nmea_topic_driver.py

Published Topics

nmea_sentence (nmea_msgs/Sentence)

• A single time-stamped NMEA sentence captured from the serial device

Parameters

~port (string, default: /dev/ttyUSB0)

• The device path

~baud (int, default: 4800)

• The baud rate to receive NMEA data.

~frame_id (string, default: gps)

• The frame_id for the header of the nmea_msgs/Sentence and output message. Will be resolved with tf_prefix if defined.

Troubleshooting

If you are using this package for the first time and encountering problems you should first check that the package installed correctly and in the right location. Then consult ROS/Troubleshooting, FAQ and http://answers.ros.org/questions/ to see if a solution has already been identified for your problem.

If you are having trouble with nmea_serial_driver and connecting to a serial port, ensure that the user has permission to access the port by checking to see if the user is part of the "dialout" group. See here for more information.

Report a Bug

Use GitHub to report bugs or submit feature requests. [View active issues]