What are the Units of Measure for the ZAREALAND & MAREALAND fields in the 2010 ZCTA to Metropolitan and Micropolitan Statistical Areas Relationship File published by the United States Census Bureau?
Image from the Explanation of the 2010 ZCTA to Metropolitan and Micropolitan Statistical Areas Relationship File [PDF]
Since the file is a relationship file between ZCTA and MSA, it represents the area in square meters that the whole ZCTA (ZAREALAND) covers, and the area that the whole MSA (MAREALAND) covers. If you notice a difference between ZAREA and ZAREALAND, or MAREA and MAREALAND, this is because there is a waterbody in that area and the *AREALAND counts only land area instead of all.
The Census Bureau uses scientific measurement units, hence meters.
