Log Webots position

e-puck2.wbt

#VRML_SIM R2020b utf8
WorldInfo {
  info [
    "The model of the e-puck 2 robot"
  ]
  title "e-puck simulation"
  coordinateSystem "NUE"
}
Viewpoint {
  orientation 0.04913069345659068 0.9922428678493876 0.11419398479121845 3.8679
  position -0.22134442152396674 0.09258687079617126 -0.19815687940397006
  follow "e-puck2"
}
TexturedBackground {
}
TexturedBackgroundLight {
}
RectangleArena {
  floorSize 2 2
}
WoodenBox {
  translation -0.2 0.05 0.683174
  rotation 0 1 0 0.5
  size 0.1 0.1 0.1
}
WoodenBox {
  translation -0.75 0.05 -0.35
  rotation 0 1 0 4.96782
  name "wooden box(1)"
  size 0.1 0.1 0.1
}
WoodenBox {
  translation 0.5 0.05 0.35471
  rotation 0 1 0 5.36782
  name "wooden box(2)"
  size 0.1 0.1 0.1
}
WoodenBox {
  translation -0.3 0.05 -0.36
  rotation 0 1 0 5.36782
  name "wooden box(3)"
  size 0.1 0.1 0.1
}
WoodenBox {
  translation -0.65 0.05 0.66
  rotation 0 1 0 5.36782
  name "wooden box(4)"
  size 0.1 0.1 0.1
}
E-puck {
  translation -0.04633846669838243 -5.5929604977326616e-05 -4.043778093383073e-05
  rotation 0.0008774908405972536 0.9999992265351687 -0.0008814413700977869 1.570339375877006
  name "e-puck2"
  controller "gps_logger"
  version "2"
  camera_width 160
  camera_height 120
  turretSlot [
    # Important! GPS is added to the turret slot!
    GPS {
    }
  ]
}

gps_logger.py

import os
from pathlib import Path
import matplotlib.pyplot as plt
from controller import Robot


# Change this! Path to plot.
PLOT_FILENAME = os.path.join(str(Path.home()), 'Pictures', 'plot.pdf')


robot = Robot()
timestep = int(robot.getBasicTimeStep())

# Enable motors to move the robot in a circle
left_motor = robot.getMotor('left wheel motor')
right_motor = robot.getMotor('right wheel motor')
left_motor.setPosition(float('inf'))
right_motor.setPosition(float('inf'))
left_motor.setVelocity(0.1)
right_motor.setVelocity(0.5)

# Enable GPS
gps = robot.getGPS('gps')
gps.enable(timestep)

# Sample robot's location
xs = []
ys = []
while robot.step(timestep) != -1:
    # By default, Webots use NUE coordinate system.
    # This can be changed in `WorldInfo` to ENU system.
    # See: https://github.com/cyberbotics/webots/pull/1643
    # However, here we do conversion for GPS only.
    x = - gps.getValues()[2]
    y = gps.getValues()[0]
    xs.append(x)
    ys.append(y)

# Make and save the plot
plt.plot(xs, ys)
plt.savefig(PLOT_FILENAME)
print(f'The plot is saved to {PLOT_FILENAME}')