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Using ArcGIS COGO tool for ROW / Easement digitizing from old plats (using their bearings and distance calls) that used what a veteran of the county says were 'made up" coordinate systems in Maryland. Several cities supposedly had their own "made up" coordinate systems.

See this plat for example

Does this veteran's story sound correct? I have contacted several people at state archives (source of the old plats) but no one there has answers to where / what these old coordinate systems are.

Is it possible in ArcGIS COGO or QGIS to recreate these "made up" coordinate systems, do the bearings / distance digitizing, and then transform them for use in Maryland State Plane 1900?

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I sometimes call these "local coordinate reference systems" as they're designed to be used in this particular area and may not have any connection to a coordinate reference system that covers a larger area.

There's usually a point-of-beginning (POB) and then metes and bounds (angles and distances) are used to survey the rest of the property / subdivision / etc.

Newer surveys usually tie-in to control points and may have State Plane or geodetic coordinates for at least the POB.

Given a POB in a "known coordinate reference system" (not local) and the angle reference, a COGO system should be able to fit in the survey, more or less. Without that, the COGO software can build the survey, but you would still have to transform or adjust it to fit with whatever coordinate reference system you want to use.

  • We use a COGO method for these unknown coordinate systems called "build it out in space, then move / rotate into place". Is the same thing as the COGO software can build the survey, but you would still have to transform or adjust it to fit with whatever coordinate reference system you want to use. – sirgeo Aug 1 '18 at 17:49
  • got an email this afternoon from state archives saying "there is no magic formula or easy way to translate these “unknown” coordinates to a known horizontal datum such as NAD 27, NAD 83/91, WGS 84, etc. without setting control points in the field and conducting field surveys. These “unknown” coordinates were generally on an assumed datum and were created in the office by the surveyor to facilitate in performing linear and area computations. They have no real meaning in affixing these points to actual geographic locations." – sirgeo Aug 1 '18 at 19:44

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