On 06/25/2017 11:05 AM, wrote:
I am studying a surveyor's map of the neighborhood where I live. The map is on record at the County Clerk's and is known as "the Plat" for my neighborhood. For some of the patios, it notes coordinates for north (or south) and east (or west), relative to some point but clearly not latitude and longitude GPS coordinates.

Where do you live? You may be looking at SPCS (State Plan Coordinate
System) coordinates widely used in the US.

http://gisgeography.com/state-plane-...e-system-spcs/

Probably more than you wanted to know.