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2012-05-04 11:19:16 -0600 answered a question turtlesim initialises at x=[inf], y=[inf], theta=[0.000000]

answering my own question 2) : it turns out that it -is- possible to hard-set the location and orientation of the turtle. This can be accomplished by issuing the following command:

$ rosservice call /turtle1/teleport_absolute -- [X] [Y] [theta]

where [X],[Y], and [theta] are float numbers.

For example:

$ rosservice call /turtle1/teleport_absolute -- 0.0 0.0 90.0

puts the turtle in the lower left corner pointed upward.

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2012-05-01 04:37:30 -0600 asked a question turtlesim initialises at x=[inf], y=[inf], theta=[0.000000]

When I execute

~$ rosrun turtlesim turtlesim_node

an empty blue "TurtleSim" simulation window pops up and the following messages are issued:

$ rosrun turtlesim turtlesim_node
QGtkStyle was unable to detect the current GTK+ theme.
[ INFO] [1335558676.993640551]: Starting turtlesim with node name /turtlesim
[ INFO] [1335558677.369623672]: Spawning turtle [turtle1] at x=[inf], y=[inf], theta=[0.000000]


Question 1 (of 2): Why is turtle1 spawned at a location beyond the end of the universe, instead of at its origin [0,0] ?


I executed

~$ rosrun turtlesim turtle_teleop_key

to see if the [x,y] coordinates would change when the up/down arrow keys were pressed, but unfortunately this is not the case. The [theta] value however -does- respond when the left/right arrow keys are pressed.

Output of the /turtle1/command_velocity topic:

$ rostopic echo /turtle1/command_velocity
linear: 2.0
angular: 0.0
---
linear: -2.0
angular: 0.0
---
linear: 0.0
angular: 2.0
---
...

Output of the /turtle1/pose topic:

...
---
x: inf
y: nan
theta: -3.06081461906
linear_velocity: 0.0
angular_velocity: 2.0
---
x: inf
y: nan
theta: -3.02881479263
linear_velocity: 0.0
angular_velocity: 2.0
---
x: inf
y: nan
theta: -2.99681472778
linear_velocity: 0.0
angular_velocity: 2.0
---
...


Question 2 (of 2): Is there perhaps a way to hard-set the [x,y] location ? E.g. something in the line of a command like "set turtle_pos=[0,0]" ?

2012-04-26 06:35:41 -0600 asked a question building beginner_tutorials returns "No Makefile in package" errors

I'm new in the world of ROS and have just installed ROS (Fuerte). I'm trying to make my way through the tutorial steps, but I'm encountering some problems. When I execute 'rosmake beginner_tutorials' in step 4 (1.2.1. Using rosmake) I get the following messages:

[rosmake-0] Starting >>> std_msgs [ make ]                                                                                   
[rosmake-0] Finished <<< std_msgs ROS_NOBUILD in package std_msgs
 No Makefile in package std_msgs                           
[rosmake-0] Starting >>> roslang [ make ]                                                                                    
[rosmake-0] Finished <<< roslang ROS_NOBUILD in package roslang
 No Makefile in package roslang                              
[rosmake-0] Starting >>> rospy [ make ]                                                                                      
[rosmake-0] Finished <<< rospy ROS_NOBUILD in package rospy
 No Makefile in package rospy                                    
[rosmake-0] Starting >>> roscpp [ make ]                                                                                     
[rosmake-0] Finished <<< roscpp ROS_NOBUILD in package roscpp
 No Makefile in package roscpp                                 
[rosmake-0] Starting >>> beginner_tutorials [ make ]

The building process completes quickly and reports 0 failures.

The above messages and the short building time are not what I expected based on the tutorial information.

What is going wrong here ?