devtrackers.gg
I'll link you a video at the end of this post which describes what our "Spotting" system is. Detection can be a complex and bizarre mechanic for newer players, so it's worth going through the video.
In general, "Spotting Damage" is gained when a ship shoots at something it cannot see. The teammates that CAN see that ship, will get "Spotting Damage" awarded to them because of their rendering assistance to their team. They get approximately 1/10th of the rewards for the damage done, I believe.
The comments talking about using Smoke in Destroyer is to help facilitate this:
You provide Smoke to your team which allows your teammates to hide in/behind.
Your teammates behind the smoke cannot see through it
Using your Destroyer, you spot targets for your team
Your teammates shoot at targets that are "Spotted" by you, their teammate.
You are awarded "Spotting Damage" for the task of lighting a target for a teammate which cannot see it otherwise.
Playing a Destroyer in front of your team by a few kilometers will often allow you to see things and help give your team vision. Playing further than 4-5 kilometers might mean you encounter an enemy ship while your team is too far to help... so be conscious of your and your teammates positioning.
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Here's the video that describes our Detection system
Direct Video Link: https://www.youtube.com/watch?v=OgRUSmzcw2s
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Further, if you attempting to farming "Spotting Damage" in Co-Op Battles, this video may give you some help.
Direct Video Link: https://www.youtube.com/watch?v=fvEw1LayGRE