The OSGB36 vs WGS84 Legal Standard
The UK Ordnance Survey National Grid (OSGB36) was originally based on the Airy 1830 ellipsoid. Modern GNSS systems natively output WGS84 (or the European realization, ETRS89).
If you naively plot a WGS84 coordinate onto an OSGB36 map without an official transformation, an absolute positional error of approximately 100 to 130 meters will occur, depending on localized grid distortion. Ordnance Survey mandates the use of the OSTN15 grid transformation to mathematically map ETRS89 geometries onto the OSGB36 standard, ensuring civil scale compliance across the mainland.
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地殻変動と再施工リスク：NAD83 vs WGS84の累積誤差
北米プレートは年間約2cm移動するため、NAD83(2011)とWGS84(G1762)は現在2.2メートル以上乖離しています。 高精度なNAD83地籍杭打ちに「標準的な」GPS WGS84座標を使用したことで、基礎のやり直しやインフラの配置ミスによる5万ドルの専門家責任賠償請求が発生しています。