Magnetic Shift and Land Survey Considerations

Legal Ramifications for Official Land/Title Survey

From: Ric Owen Hatfield <richowenhatfield{at}yahoo{dot}com>
To: sterlingda@pureenergysystems.co*m
Sent: Monday, February 28, 2005 1:20 AM
Subject: source of magnetic north data

Several years ago I worked with land surveyors. We used a theodolite to determine the legal boundaries of land and for the placement of legal markers, such as an iron pin at property corners. After the survey, all angles were recorded on the plats relative to magnetic north. Previous land survey plats were always the basis of the new survey. These records are kept at the courthouse in the county wherein the land lies.

We often found that the older documents did not match our new measurements. We usually attributed this to a technology gap, today's instruments being more accurate and using lasers etc. as opposed to chains and angle measurers. We also attributed differences in measurements to the previous surveyor's expertise.

An interesting study would consist of comparing older property plats with the most recent ones. If magnetic north measurements are consistently skewed in a certain direction, this could give valuable insight. the data for this investigation is already in the courthouse deed and records rooms across the nation.
Owen Hatfield
Rockmart, GA

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Additional Legal/Land Survey Considerations

From: "Kearn Larkin"
Sent: Wednesday, March 02, 2005 8:55 AM
Subject: Re; Owen Hatfield/Magnetic field

Variation in the magnetic field has been taken into consideration for centuries, and it has been recognized that there's a shift in this variation. USCGS publishes tables on this with periodic revisions, and the variation for a given location can be determined by shooting a bearing on Polaris and comparing it to a compass bearing.
Ideally, a survey using magnetic bearings would include the contemporary variation, permitting current variation to be factored in. Less precise (and not allowing for local anomaly) it is possible to look up the historic regional variation for the date on the survey - or, more convenient on location, a bearing can be shot on existing landmarks and the compass bearings can be compared to those on the original survey to derive a conversion factor.
When a current survey does not agree with a previous survey it would trigger an investigation into the source of the error. Not to do so would invite certain legal complications.