While online maps aren't known for precise accuracy, there are times when seconds count (ie slight errors made by surveyors). Although these may be approximations within an acceptable range of error, the precision is needed for differential purposes. Oceania is defined as as Australia and its possessions, New Zealand, the eastern half of New Guinea, and all of Melanesia, Micronesia and Polynesia. Only states that have been recognised by over 50% of the U.N. fully included. Dependencies do not count on this quiz, but integral parts of countries whose mainland is elsewhere do. East and west are relative to the centre of the area as opposed to dependent on the 180th meridian.
Since there is some debate as to whether external territories of Australia count as 'integral parts of the country,' I've included only inhabited territories. Suggestions, comments and corrections always appreciated, especially since Oceania is almost completely islands and I may have missed one or two.