when using stage simulation some problem occured with global localizaton

[fighterxi]

Hi,
sorry to trouble you! I'm using the stage simulator doing some path tacking work. I need a global and perfect position to make it, so the topic “base_pose_ground_truth” would be perfect for it. Also In order to eliminating the error of odom, I used the officially recommended "gps" rather than "odom". Still, you will see a large shift in the “odom ” coordinate relative to the global coordinate （map）, especially when the robot is turning.
As far as I know, both of these ("gps" " base_pose_ground_truth" )come from the stage simulator , and the coordinate system mentioned above should not have relative movement(or drift ).
Can you told me what can I do to get the global positioning more precise?

this is the param in stage
——————————
`define difflike_robot position
(
pose [ 0.0 0.0 0.0 0.0 ]

#odom_error [0.00 0.00 999999 999999 999999 0.00]
localization "gps"
localization_origin [ 0 0 0.0 0.0]`