Read GPS module data

This function is to obtain longitude, latitude and altitude data by reading GPS module data and parsing GPS data through the terminal.

1. Read GPS data through the terminal

terminal input:

roslaunch nmea_navsat_driver nmea_serial_driver.launch

Then we look at the topic data, the terminal input:

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rostopic list

Regarding the data on these topics of GPS, here is an explanation.

For each topic message type, please refer to the official website URL,

gps_common/GPSFix Documentation (ros.org)

sensor_msgs/NavSatFix Documentation (ros.org)

sensor_msgs/TimeReference Documentation (ros.org)

geometry_msgs/TwistStamped Documentation (ros.org)

We can print out these topic messages on the terminal, and what we get is the GPS data. Take printing /fix as an example, the terminal input

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rostopic echo /fix

The terminal will print out the following data,

Among them, latitude, longitude, altitude represent latitude, longitude and altitude respectively.

2、Read the latitude, longitude and altitude of GPS data

terminal runs,

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roslaunch nmea_navsat_driver nmea_serial_driver.launch
rosrun nmea_navsat_driver read_lat_long.py 

The data printed by the terminal is the latitude, longitude and altitude of the current GPS module, look at the source code, read_lat_long.py

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#! /usr/bin/env python
# -*- coding: utf-8 -*-
import rospy
from sensor_msgs.msg import NavSatFix

def GPSCallback(msg):
    rospy.loginfo("latitude:%0.6f, longitude:%0.6f,altitude:%0.6f", msg.latitude, msg.latitude,msg.altitude)    
def GPS_subscriber():
    rospy.init_node('GPS_subscriber', anonymous=True)# ROS节点初始化
    rospy.Subscriber("/fix", NavSatFix, GPSCallback)
    rospy.spin()# 循环等待回调函数
if __name__ == '__main__': 
    GPS_subscriber()

The program subscribes to the data of the /fix topic, then parses it in the callback function, and finally prints it to the terminal.