In general, standard reiatsu detection gives intensity and direction. With other means being employed by shinigami and arrancar to pinpoint location (Bakudo 71 and Pesquisa, to be specific).

And I would expect you to not be able to determine who a reiatsu belongs to unless you have met that person. You could off course tell the reiatsu apart if you felt it a second time without meeting the owner. Let me give an example situation.

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Kazuo: "I feel a spiritual pressure... It belongs to Carmelia, the hollow."

Someone: "Who?"

Kazuo: "I have no idea, never met this hollow, but I know it belongs to her... Somehow."

Someone: "Is she on your database?"

Kazuo: "No, the only time she fough someone was a mortal named Hasunaga."

Someone: "Who?"

Kazuo: "I have no idea either. I don't know where those names are coming from."

...

Draken: *sips tea*

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Hope that was as silly and amusing to you as it was to me.