I believe this is the first of a several linked areas that need to be resolved so that constructive progress on diplomacy can occur.
- Issues
* Tends to require continual re-sweeping of your empire and surroundings with high detection ships to make sure there's not a hidden fleet, or planet somewhere.
* * Against stealthy opponents for optimal play would require recording where you've scanned, when most recently, and at what power.
* Cannot translate into a meaningful detection range GUI. We have "Detection range circles" which are simple and misleading, or the fiddly, guess-based "Galaxy map stealth threshold slider."
* Requires some sort of additional level of fleet commands: weather ships should hide or fight/blockade.
* Leads to annoying, inconclusive "battles" where one side hunts for ships that don't want to be found.
** How do you start a battle with utterly undetected ships in your system, when if you might detect them if you manage to maneuver your ships close enough?
I see two alternate systems that can resolve the issues. These systems could be combined to some degree, but for simplicity, i'll describe them separately. The following describes the galaxy map.
A) Zones of Certainty & Uncertainty
The area every detector scans is divided into two parts:
1) an inner circle within which all things are detected.
2) an outer circle where things might be detected depending on how stealthy they are and how close to the inner circle of certain detection.
3) outside both circles nothing is detected, unless it is universally visible.
An object with a stealth of zero would be detected on the edge of the outer circle. More stealthy objects would need to be progressivly closer to the inner circle to be detected. Something with a stealth of 100 would be detected only on the edge of the inner circle.
No new stats are needed and the same FO-script can probably be used, with new underlying mechanics. The radius of the outer circle is determined by the detector strength. The inner circle is a standardized fraction of the other's radius-- perhaps between 1/5th & 1/3rd.
Primary consequence: you will detect all things in the same system ( galaxy map distance: 0) as your detector. However, you may not have all information on the objects, depending on if and how espionage is implemented. For instance detecting an enemy colony wouldn't necessarily tell you it's focus, or population. Espionage might be required for that.
B) Progressive Detection
Detectors have one stat, which determines the range at which things can be detected. No object inside the detection area is totally invisible. No object outside is visible. However, detecting an object doesn't mean you know everything about it. For instance, a fleet of highly stealthed ships, might hide the number and type of ships or even which empire owns them. As the ships draw closer to the detector, more details are revealed, until at the same location, full disclosure is achieved. Of course if an espionage system is implemented, there might be information about a fleet or colony that can only be gained via espionage, not normal detectors.
It is possible that in some circumstance all that is revealed is the class of object, i.e. "huge planet", or "non-allied fleet". But at minimum you'll know something is there and you can act on it or against it. You know where to bring your more powerful scanners to bear.
C) Exceptions and Qualifications to Both the Above
1) Espionage
If Espionage is implemented, then there could be a weaponless class of spy ship that might be totally invisible, if the stealth tech is better than the detection tech. These might perform spy missions or simply provide vision. Since they are weaponless they would not cause ambiguous or complicated situations figuring out if and when they should reveal themselves and effect blockades or battles.
2) Universally Visible
Certain rare, very important objects might be visible at any distance, no matter how low detection is. For instance a precursor invasion.
3) Space Combat
I would prefer that detection in space combat is keep similar to the galaxy map, but i'm not primarily concerned with it at this time. Most of the issues are specific to the galaxy map. I originally objected to the idea that you might be able to detect a fleet on the galaxy map, but not necessarily be able to see it in combat. But gameplay should always trump even plausibility. Besides you can easily technobabble that the high energy required to jump makes any ships detectable when they leave or enter a system.