How does invisibility interact with detect alignment?

Question

Suppose I am a lawful good invisible guy in the presence of an evil creature which has an ability equivalent to "detect good", is it sufficient to overcome my invisibility? What if I keep moving so the creature cannot concentrate long enough in my area?

Answer 1

First, if your character's aura is not strong enough (lvl 4 or lower), detect good can't detect him. I assume it's not your case.

Then, as the description of detect evil states:

You can sense the presence of evil. The amount of information revealed depends on how long you study a particular area or subject.

1st Round: Presence or absence of evil.

2nd Round: Number of evil auras (creatures, objects, or spells) in the area and the power of the most potent evil aura present.

[...]

3rd Round: The power and location of each aura. If an aura is outside your line of sight, then you discern its direction but not its exact location.

So basically if you stay 3 rounds in the area of the spell, the creature will know your location. You will still be invisible, though, with complete camouflage and all the other bonuses.

Depending on how your GM read the rules, the creature may or may not see your lingering aura. As written, the lingering aura is only left if you are "destroyed" but I have seen GMs considering a moving creature should leave one behind it when moving:

Lingering Aura: An evil aura lingers after its original source dissipates (in the case of a spell) or is destroyed (in the case of a creature or magic item). If detect evil is cast and directed at such a location, the spell indicates an aura strength of dim (even weaker than a faint aura). How long the aura lingers at this dim level depends on its original power:

Faint: 1d6 rounds

Moderate : 1d6 minutes

Strong: 1d6x10 minutes

Overwhelming: 1d6 days

This lingering aura should be enough for this creature to follow your trail if there is no other source of good aura, if your GM stated you leave one behind you.

Answer 2

Detect Good gives information based on how long the creature using it observes an area:

1st Round: Presence or absence of good.

2nd Round: Number of good auras (creatures, objects, or spells) in the area and the power of the most potent good aura present.

If you are of evil alignment, and the strongest good aura’s power is overwhelming (see below), and the HD or level of the aura’s source is at least twice your character level, you are stunned for 1 round and the spell ends.

3rd Round: The power and location of each aura. If an aura is outside your line of sight, then you discern its direction but not its exact location.

Invisibility does not protect against any of this, but not being in the area affected certainly does. Let's break this down further:

• You are hiding in a footlocker while invisible. The detect good guy walks by.
  • The spell does detect the presense of good and, after a round, gives your rough level estimate and then, after two rounds, your direction. After opening the locker, the guy then gets your precise location (since he then has line of sight). Probably somewhere in here you realize you've been spotted and attack him, for example when he opens the locker without being able to tell where you are.
• You are hiding in a corner while invisible. The detect good guy walks by.
  • The spell does detect the presence of good and after two rounds gives your precise location, since he has LOS.
• You are hiding in a corner while invisible. When your Sense Motive skill tells you you've been spotted, you immediately move behind the guard and out of his cone of detection.
  • The spell does not detect the presence of good (although it already did so), because you are no longer in the area. The diviner must now continue to search for you and as long as you keep correctly guessing where the invisible magic detection cone is pointed, your invisibility may well conceal your location.
• You are hiding in a corner invisible and with your permanent Enlarged Widened Arcane Sight active. The diviner approaches, but you see his Detect Good long before he sees your Good alignment. You prepare to sprint past him when he gets 65 feet away, then do so in a straight line, making use of diagonalization rules to end your 120 ft movement 65 feet away on the other side.
  • You are detected. Certainly the spell cannot detect you at the end of your movement, nor at the beginning, but it will register you passing through in the interim. The diviner will have no information as to what direction you entered in from or left in, however.
• You are walking along and walk into someone with Detect Evil standing sentry
  • You are detected, and the diviner also learns your precise location immediately, having studied the area for more than 3 rounds.
• You are in plumbic full plate.
  • The spell cannot detect you unless the diviner is also inside your full plate.
• You leave a hiding place after not casting any spells with the [good] descriptor and the diviner searches it shortly afterwards, hoping for dim auras.
  • The diviner does not detect you or find any trace auras, as you did not recently die in that location.