The data quality assessment is a summary of an observation's accuracy. All observations start as "casual" grade, and achieve "research" grade when

• the iNat community agrees with the observer's ID, where an "agreeing" identification is one that matches exactly or is of a child taxon of the observer's ID. For example, if Scott says it's a mammal and Ken-ichi says it's Homo sapiens, then Ken-ichi agrees with Scott.
• the observation has a date
• the observation is georeferenced (i.e. has lat/lon coordinates)
• the observation has a photo

Observations will revert to "casual" grade if the above conditions aren't met or

• the community agrees the location doesn't looks accurate (e.g. monkeys in the middle of the ocean, hippos in office buildings, etc.)
• the community agrees the organism isn't wild/nat