According to Concealment, you can use spot vs hide (with relevant modifiers) to discover the square an invisible creature occupies. This agrees with the description of Hide.
According to Invisibility... well, I want to say this rephrases the information from hide, but in plain english it says something entirely different:
Spot agrees with this, although since it's in the PHB it's a lot less specific:A creature can generally notice the presence of an active invisible creature within 30 feet with a DC 20 Spot check. The observer gains a hunch that “something’s there” but can’t see it or target it accurately with an attack. A creature who is holding still is very hard to notice (DC 30). An inanimate object, an unliving creature holding still, or a completely immobile creature is even harder to spot (DC 40). It’s practically impossible (+20 DC) to pinpoint an invisible creature’s location with a Spot check, and even if a character succeeds on such a check, the invisible creature still benefits from total concealment (50% miss chance).
So taking Invisibility's excerpt piece by piece:Originally Posted by Spot
- Within 30 feet, you can sense the presence of an invisible creature with a DC20 spot check.
- If it's still, the DC is 30.
- If it's not alive and still, the DC is 40.
- +20 To DC to spot the location of an invisibile creature. From context we know that this is referring to the flat DC. So any living being's location is known with a DC50 spot, at most.
- We know it's not referring to the opposed roll, because (a) context is all about the flat roll, and (b) it would list +40 not just +20 if it were.
So basically, a 5th level rogue can stand still with a wand of invisibility, but despite his +75 hide modifier, someone can see his precise location with a 50. In fact, once your hide modifier passes +40, you are less visible if you're visible, because people can't just point to your square and lob glitterdusts.