No GPS noise in Gazebo Sim

PX4 Autopilot
1

Hi,

I would like to have no gps noise in my gazebo sim (not gazebo classic). I have been trying to follow the instructions in Gazebo Simulation | PX4 Guide (main)

I see the instructions on how to eliminate sensor noise for gazebo classic: Gazebo Classic Simulation | PX4 Guide (main)

However the in gazebo sim there is no

<gpsNoise>true</gpsNoise>

in the sdf file. From my understanding the .sdf files of gazebo classic and gazebo sim are not transferable.

I also have been following the instructions in post Eliminating all sensor noise and bias
However based on the instructions, I think this is also for gazebo classic based on the dates of the question.

What I have tried:

in the default.sdf I looked for anything ‘gps’ but could not find anything

I then commented out the following in DataValidator.cpp

	//} else if (_value_equal_count > _value_equal_count_threshold) {
	//	/* we got the exact same sensor value N times in a row */
	//	_error_mask |= ERROR_FLAG_STALE_DATA;
	//	ret = 0.0f;

I modified the following lines in SensorGpsSim.cpp

double latitude = gpos.lat; //+ math::degrees((double)generate_wgn() * 0.2 / CONSTANTS_RADIUS_OF_EARTH);
double longitude = gpos.lon; //+ math::degrees((double)generate_wgn() * 0.2 / CONSTANTS_RADIUS_OF_EARTH);
float altitude = gpos.alt; //+ (generate_wgn() * 0.5f);

I modified the following lines in SensorBaroSim.cpp to eliminate the noise and drift (I added and then subtracted the noise so I would not get the build error of a variable not used):

const float absolute_pressure_noisy = absolute_pressure + abs_pressure_noise + _baro_drift_pa - abs_pressure_noise - _baro_drift_pa ;

I could not find the “gazebo_imu_plugin and gazebo_barometer_plugin” in the default.sdf for gazebo sim.

I then did a

make clean
make distclean
make px4_sitl

However, all of this did not work :frowning: . I feel this should be something simple based on how simple the approach is in the gazebo classic instructions, you just have to eliminate one line in the world .sdf (true).

I am using ubuntu 22
PX4 v 1.14
Gazebo Garden 7.7

If someone could show how to eliminate sensor noise in gazebo sim, I would really appreciate it! Thanks!

2

Could it come from here?

3

I don’t think so :frowning: I commented out everything past the gpos.lat and gpos.long (and gpos.alt) and I still see the gps bouncing around when my drone is stationary on the ground.

4

Hang on, are you using classic or new Gazebo?

5

For classic it should be here:

6

I am using new Gazebo.

I am a big fan of how simple the change for no noise is for gazebo classic - I wish there was something for the new gazebo - and if there is does anyone know how it is done?

7

So gpssim is not what’s used for new Gazebo? We have to figure out which module runs and publishes gps.

8

I did some digging and from what I found, it looks like new gazebo uses NavSat:

According to SDFormat Specification, it looks like you can specify no noise. SDFormat Specification

which corresponds to what I see in gz-sensors/src/NavSatSensor.cc at 08ab86ba271007b0f54f4a26932e194ee1ad236d · gazebosim/gz-sensors · GitHub in lines 120-148.

However I tried adding this to the model.sdf:

<sensor name="navsat_sensor" type="navsat">
  <always_on>1</always_on>
  <update_rate>1</update_rate>
  <topic>navsat</topic>
  <navsat>
    <position_sensing>
      <horizontal>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.0</stddev>
        </noise>
      </horizontal>
      <vertical>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.0</stddev>
        </noise>
      </vertical>
    </position_sensing>
    <velocity_sensing>
      <horizontal>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.0</stddev>
        </noise>
      </horizontal>
      <vertical>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.0</stddev>
        </noise>
      </vertical>
    </velocity_sensing>
  </navsat>
</sensor>

But then when I tried to spawn the gazebo world with the model, the model did not load :frowning:

Am I going about this right way? The only other sensors I see in the model.sdf is the imu_sensor and the air_pressure_sensor. So I really don’t know how the model is getting its gps information to begin with because navsat is not already existing in the model.sdf