[Bug] sitl_multiple_run for gazebo-classic starts with wrong mav_sys_id

[av-jeroen]

Describe the bug

When executing the SITL multiple drones bash script for gazebo-classic multiple drones are being deployed. The Mavlink system Ids should start at 1 and increase for every drone. Instead it starts at 2.

Before 1.14 this was the way it worked, and I belief this is the way people will expect it to work.

To Reproduce

The bug is visible when running with one drone:

./Tools/simulation/gazebo-classic/sitl_multiple_run.sh

But also with multiple

./Tools/simulation/gazebo-classic/sitl_multiple_run.sh -n 3

Expected behavior

Expected: The MAV_SYS_ID of the first drone should be 1.
Actual: The MAV_SYS_ID of the first drone is 2.

Software Version

1.14.0 and up

Flight controller

SITL

Vehicle type

Multicopter

[av-jeroen]

Solved by changing the following in ./Tools/simulation/gazebo-classic/sitl_multiple_run.sh

spawn_model ${vehicle_model} $(($n + 1))

into

spawn_model ${vehicle_model} $n

Not sure if this was intended behaviour, maybe certain developers want to run this next to a SIH setup?

I'll close it for now.

[Jaeyoung-Lim]

@av-jeroen Please consider creating a PR if you think this is a modification needed to improve the repository.