Added magnetometer value based on location

[ahcorde]

🦟 Bug fix

Summary

The magnetometer sensor is publishing a value but it's not based on the location. This PR calculate the value based on the location.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[mjcarroll]

I think that we need some documentation on the derivation of these tables. It's worth-while to note that these are for a) earth only and b) only valid in a certain window (I think they are updated every 5 years).

A more generic solution would allow for the consumption of the world magnetic model: https://www.ncei.noaa.gov/products/world-magnetic-model, but I understand if that's out of the scope of the current PR.

[ahcorde]

I used this code from this other Gazebo classic plugin https://github.com/PX4/PX4-SITL_gazebo-classic/blob/5610c3fb441a2f3babc8ad7a63c8c4ce3e40abfa/src/geo_mag_declination.cpp

[mjcarroll]

I used this code from this other Gazebo classic plugin

Ah, makes sense, all good then. I think the only other thing I would request is a switch to be able to switch between a constant magnetic declination/field and a varying one. That way people can opt into the new behavior (in the unlikely case someone was depending on a constant field?)

[ahcorde]

I used this code from this other Gazebo classic plugin

Ah, makes sense, all good then. I think the only other thing I would request is a switch to be able to switch between a constant magnetic declination/field and a varying one. That way people can opt into the new behavior (in the unlikely case someone was depending on a constant field?)

the spherical coordinates should turn on and off this feature.

[mjcarroll]

the spherical coordinates should turn on and off this feature.

Perfect, I think that is reasonable.

[codecov]

Codecov Report

Merging #1907 (7f7e2dd) into gz-sim7 (3dc8c7a) will decrease coverage by 0.15%.
The diff coverage is 63.12%.

❗ Current head 7f7e2dd differs from pull request most recent head bed28ab. Consider uploading reports for the commit bed28ab to get more accurate results

@@             Coverage Diff             @@
##           gz-sim7    #1907      +/-   ##
===========================================
- Coverage    64.68%   64.54%   -0.15%     
===========================================
  Files          343      347       +4     
  Lines        27430    27766     +336     
===========================================
+ Hits         17743    17921     +178     
- Misses        9687     9845     +158     

Impacted Files	Coverage Δ
include/gz/sim/Util.hh	100.00% <ø> (ø)
...rc/systems/ackermann_steering/AckermannSteering.hh	100.00% <ø> (ø)
src/systems/joint_controller/JointController.hh	100.00% <ø> (ø)
...int_position_controller/JointPositionController.hh	100.00% <ø> (ø)
src/systems/magnetometer/Magnetometer.cc	51.77% <10.86%> (-20.86%)	⬇️
src/gui/plugins/component_inspector/Inertial.cc	11.76% <11.76%> (ø)
src/SdfGenerator.cc	90.33% <40.00%> (-0.62%)	⬇️
src/systems/apply_link_wrench/ApplyLinkWrench.cc	77.77% <46.15%> (ø)
...int_position_controller/JointPositionController.cc	74.13% <67.56%> (+0.56%)	⬆️
src/Util.cc	91.29% <71.42%> (-0.95%)	⬇️
... and 15 more

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[mjcarroll]

LGTM with green ci

[mjcarroll]

CI Failures here aren't from this PR.