Why NAD27 to NAD83 Conversions Cause Boundary Disputes の座標変換

Technical Summary: The historic shift from the Clarke 1866 ellipsoid to the GRS80 ellipsoid created significant metric offsets that still haunt legacy property lines today.
実務リスク警告

誤った測地系（データム）の指定や、グリッド・地上補正（Grid-to-Ground）を適用しない座標変換は、1〜400mの位置ズレを引き起こします。これは測量過失請求や施工紛争の代表的な原因です。

技術事例・判例を見る 契約上の測地系リスク リスク試算シミュレーター

Unlike the subtle 1-meter difference between NAD83 and WGS84, the shift from the historic North American Datum of 1927 (NAD27) to NAD83 was massive. The origins of the datums changed entirely (from Meades Ranch, Kansas, to the Earth's center of mass).

The Impact on Property Surveys

Because the Clarke 1866 ellipsoid was fundamentally a different shape than GRS80 (NAD83), coordinate values shifted by tens to hundreds of meters depending on the location in North America. When attempting to re-stake a property line defined by 1960s NAD27 coordinates, surveyors must use highly accurate transformation grids (like NADCON) rather than simple block shifts. Failure to do so has resulted in massive structural encroachment lawsuits.

Verify Coordinates with Core ツール一覧

Always validate your site data before mobilizing construction or legal teams. Use our built-in coordinate converters to rule out fundamental geodetic errors:

よくある技術的な質問

How far apart is NAD27 and NAD83?

The difference between NAD27 and NAD83 coordinates for the exact same physical point can range from 10 meters to over 100 meters, depending entirely on geographic location within North America.