text: # -*- coding: utf-8 -*-
  # Filename: demo_no_algo.py
  
  """
  The simplest demo of Sim.
  Only generate reference trajectory (pos, vel, sensor output). No algorithm.
  Created on 2018-01-23
  @author: dongxiaoguang
  """
  
  import os
  import math
  from gnss_ins_sim.sim import imu_model
  from gnss_ins_sim.sim import ins_sim
  
  # globals
  D2R = math.pi/180
  
  motion_def_path = os.path.abspath('.//demo_motion_def_files//')
  fs = 100.0          # IMU sample frequency
  fs_gps = 10.0       # GPS sample frequency
  fs_mag = fs         # magnetometer sample frequency, not used for now
  
  def test_path_gen():
      '''
      test only path generation in Sim.
      '''
      #### choose a built-in IMU model, typical for IMU381
      imu_err = 'mid-accuracy'
      # generate GPS and magnetometer data
      imu = imu_model.IMU(accuracy=imu_err, axis=9, gps=True)
  
      #### start simulation
      sim = ins_sim.Sim([fs, fs_gps, fs_mag],
                        motion_def_path+"//motion_def-3d.csv",
                        ref_frame=1,
                        imu=imu,
                        mode=None,
                        env=None,
                        algorithm=None)
      sim.run(1)
      # save simulation data to files
      sim.results('')
      # plot data, 3d plot of reference positoin, 2d plots of gyro and accel
      sim.plot(['ref_pos', 'gyro', 'gps_visibility'], opt={'ref_pos': '3d'})
  
  if __name__ == '__main__':
      test_path_gen()
  