error loading <rosparam> tag in px4_config.yaml

[senthilarul]

I tried running the px4 sitl on gazebo with mavros and encountered this issue:

error loading <rosparam> tag:
        file /home/catkin_ws/src/mavros/mavros/launch/px4_config.yaml contains invalid YAML:
could not determine a constructor for the tag '!degrees'
in "<string>", line 63, column 27:
angular_velocity_stdev: !degrees 0.02
^
XML is <rosparam command="load" file="$(arg config_yaml)"/>
The traceback for the exception was written to the log file

I have previous tried running the multi uav simulation and had no trouble with it. Recently I had to create a fresh installation on a new computer and I am having trouble running mavros and px4 sitl together. How should I rectify this issue?

Any help is appreciated. Thanks in advance.

[Dines97]

I have the same issue with you, I also made a clean ubuntu installation. In addition, I can say that I initially used ubuntu 16.04.5 (Everything worked here) and was updated to 16.04.6 (And here it is not)

UPD: Well, I just deleted the exclamation mark in front of the degrees in the file indicated by the error. Everything is working. Does this exclamation mark mean something?

[AnnaMiG]

I am having the same issue. Does anybody know why this is happening?

[tmarkmann]

I solved the issue by downgrading PyYAML from 5.1 to 3.13 manually with "pip uninstall PyYAML" and "pip install PyYAML==3.13"

[mrivi]

I can confirm that downgrading PyYAML from 5.1 to 3.13 works

[julianoes]

I ran into this today as well. What is this exclamation mark for?

[bys1123]

I have the same issue.

[julianoes]

For now a workaround is this change:

diff --git a/mavros/launch/px4_config.yaml b/mavros/launch/px4_config.yaml
index d199f17..a3edcce 100644
--- a/mavros/launch/px4_config.yaml
+++ b/mavros/launch/px4_config.yaml
@@ -60,7 +60,7 @@ imu:
   frame_id: "base_link"
   # need find actual values
   linear_acceleration_stdev: 0.0003
-  angular_velocity_stdev: !degrees 0.02
+  angular_velocity_stdev: "!degrees 0.02"
   orientation_stdev: 1.0
   magnetic_stdev: 0.0
 
@@ -211,7 +211,7 @@ odometry:
 # px4flow
 px4flow:
   frame_id: "px4flow"
-  ranger_fov: !degrees 6.8  # 6.8 degreens at 5 meters, 31 degrees at 1 meter
+  ranger_fov: "!degrees 6.8"  # 6.8 degreens at 5 meters, 31 degrees at 1 meter
   ranger_min_range: 0.3     # meters
   ranger_max_range: 5.0     # meters

but I assume that changes behavior and is not the right fix.

[jsalvador4]

I also have a similar error, is there any solution to fix in this case?

[julianoes]

@jsalvador4 see my answer above.

[jsalvador4]

My error appears in another line, should I also edit the !degree lines as you noted?

[julianoes]

Check what's causing your issue and see what can fix it.

[w0rt4]

mavlink/mavros@1e9d805#diff-1081d05fe29e8c7f51693863fe64cd9f
@jsalvador4 this should fix your issue (in my case i have exactly the same error and it helps)