How to subcribe tf transform from map to odom by gmapping into odom to baselink?

Question

Hi, I have an odometry obtained from encoders but it is not accurate enough. In long periods, the error accumulated the robot position not accurate. I know that gmapping publish a tf transform from map to odom. Can I subscribe this transform and add it into my odometry or the transform from odom to baselink so that the position of my robot is more accurate?

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Originally posted by mree on ROS Answers with karma: 41 on 2015-02-06

Post score: 1

Answer 1

Do not add anything manually. TF does that for you. Just use /map -> /base_link instead of /odom -> /base_link to get the robot position.

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Originally posted by dornhege with karma: 31395 on 2015-02-06

This answer was ACCEPTED on the original site

Post score: 1

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Original comments

Comment by mree on 2015-03-05:
Sorry for late reply, but my odometry transform is from odom to base_link. How could achieve directly from /amp ->/base_link

Comment by mree on 2015-03-05:
my tf tree now is /map -> /odom -> base_link

is it what you means as below? /map -> /base_link /map -> /odom

Comment by dornhege on 2015-03-05:
tf tree looks good. Just use the map->base_link transform and you'll get your pose in the map.

Comment by mree on 2015-03-06:
Currently I am getting my robot position in map by this way:

odom.pose.pose.position.x = x_move;
odom.pose.pose.position.y = y_move;
odom.pose.pose.position.z = 0.0;
odom.pose.pose.orientation = tf::createQuaternionMsgFromYaw(w_move);

Comment by mree on 2015-03-06:
do you mean i should use this lookuptransform instead of odom to get my robot pose? something like this:

try { listener.lookupTransform("map", "base_link", ros::Time(0), transform_in_map); } catch(tf::TransformException &exception) { ROS_ERROR("%s", exception.what()); }

Comment by dornhege on 2015-03-06:
Yes! .

Comment by mree on 2015-03-10:
I have made this change:

odom.pose.pose.position.x = transform.getOrigin().x();
odom.pose.pose.position.y = transform.getOrigin().y();
odom.pose.pose.position.z = 0.0;
odom.pose.pose.orientation.z =tf::getYaw(transform.getRotation());;

Comment by mree on 2015-03-10:
However, when the odom frames move, the robot remains stationary. The transform from map to odom published by gmapping and amcl is not send to the base_link

Comment by dornhege on 2015-03-10:
Do NOT change the odometry. The odometry is what it is. Run gmapping amcl or similar together with the odometry and use that output as your robot's accurate pose.

Comment by Zuhair95 on 2022-05-24:
@mree Did you solve the problem ? I mean how to get the gmapping estimated position ? Thanks in advance .

Comment by Zuhair95 on 2022-05-24:
Please, @dornhege How to "use /map -> /base_link instead of /odom -> /base_link "