If you want to add specially noise you can change your odom topic with the another name maybe old_odom and than subscribe this topic. After that you can add what ever want and publish your odom.

https://blog.lxsang.me/post/id/16

```
#! /usr/bin/env python
import rospy
from math import *
import numpy as np
from nav_msgs.msg import Odometry
import tf
last_odom = None
pose = [0.0,0.0,0.0]
a1 = 0.0
a2 = 0.0
a3 = 0.0
a4 = 0.0
base_frame = ""
# a callback for Gazebo odometry data
def callback(data):
global last_odom
global base_frame
global pose
global a1
global a2
global a3
global a4
if(last_odom == None):
last_odom = data
pose[0] = data.pose.pose.position.x
pose[1] = data.pose.pose.position.y
q = [ data.pose.pose.orientation.x,
data.pose.pose.orientation.y,
data.pose.pose.orientation.z,
data.pose.pose.orientation.w ]
(r, p, y) = tf.transformations.euler_from_quaternion(q)
pose[2] = y
else:
# calculate new odometry pose using the motion model
dx = data.pose.pose.position.x - last_odom.pose.pose.position.x
dy = data.pose.pose.position.y - last_odom.pose.pose.position.y
trans = sqrt(dx*dx + dy*dy)
q = [ last_odom.pose.pose.orientation.x,
last_odom.pose.pose.orientation.y,
last_odom.pose.pose.orientation.z,
last_odom.pose.pose.orientation.w ]
(r,p, theta1) = tf.transformations.euler_from_quaternion(q)
q = [ data.pose.pose.orientation.x,
data.pose.pose.orientation.y,
data.pose.pose.orientation.z,
data.pose.pose.orientation.w ]
(r,p, theta2) = tf.transformations.euler_from_quaternion(q)
rot1 = atan2(dy, dx) - theta1
rot2 = theta2-theta1-rot1
sd_rot1 = a1*abs(rot1) + a2*trans
sd_rot2 = a1*abs(rot2) + a2*trans
sd_trans = a3*trans + a4*(abs(rot1) + abs(rot2))
trans += np.random.normal(0,sd_trans*sd_trans)
rot1 += np.random.normal(0, sd_rot1*sd_rot1)
rot2 += np.random.normal(0, sd_rot2*sd_rot2)
pose[0] += trans*cos(theta1+rot1)
pose[1] += trans*sin(theta1+rot1)
pose[2] = theta1 + rot1 + rot2
last_odom = data
# publish the tf
br = tf.TransformBroadcaster()
br.sendTransform((pose[0], pose[1], 0),
tf.transformations.quaternion_from_euler(0, 0, pose[2]),
data.header.stamp,
base_frame,
"odom")
if __name__ == '__main__':
rospy.init_node('noisy_odometry', anonymous=True)
# alpha 1 is degree/degree
if rospy.has_param("~alpha1"):
a1 = rospy.get_param("~alpha1")
else:
rospy.logwarn("alpha1 is set to default")
a1 = 15.0*pi/180.0
# alpha 2 is degree/m
if rospy.has_param("~alpha2"):
a2 = rospy.get_param("~alpha2")
else:
a2 = 15.0*pi/180.0
rospy.logwarn("alpha2 is set to default")
# alpha 3 is m/meter
if rospy.has_param("~alpha3"):
a3 = rospy.get_param("~alpha3")
else:
a3 = 0.2
rospy.logwarn("alpha3 is set to default")
# alpha 4 is m/degree
if rospy.has_param("~alpha4"):
a4 = rospy.get_param("~alpha4")
else:
a4 = 0.01
rospy.logwarn("alpha4 is set to default")
# get odom topic
if rospy.has_param("~old_odom_topic"):
odom_topic = rospy.get_param("~old_odom_topic")
else:
odom_topic = "/odom"
# get base frame
if rospy.has_param("~base_frame"):
base_frame = rospy.get_param("~base_frame")
else:
base_frame = "/base_footprint"
rospy.Subscriber(odom_topic, Odometry, callback)
rospy.spin()
```