• National Geodetic Survey (point database)
• GPS Base Station (HAMP CORS)
• Vertical control
• US Survey Feet vs. Meters
• Northampton Coordinate System (obsolete)
• Mass Highway (point database)

Accurate surveys require survey-grade geodetic control points. Federal, State, and Municipal agencies all place, maintain, and document permanent physical control points for public use.

The current standards for survey datums are Massachusetts Mainland State Plane NAD83 (horizontal) and NAVD88 (vertical). Government coordinates are defined in meters.

Converting to & from legacy American units is tricky since there are different definitions for a "foot". Massachusetts chose US Survey Feet as an alternate standard though you must take care when converting to maintain survey-grade accuracy.

National Geodetic Survey (NGS) has free conversion software (NADCON) and information available on their website.