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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.
→ Read the Full UK Datum Authority GuideRelated Tools & Resources
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The $50,000 Geodetic Drift Liability: NAD83 vs WGS84
Because the North American Plate moves ~2cm/year, NAD83(2011) and WGS84(G1762) currently diverge by over 2.2 meters. Using a "standard" GPS WGS84 coordinate for a high-precision NAD83 cadastral staking has triggered $50,000 Professional Liability claims for foundational rework and utility misplacement.
Risk Exposure Metric:
2.2-Meter Tectonic Drift & Epoch Accumulation
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Warning: Verify Your Calculation
Coordinate accuracy varies by device and datum. Do not use these results for legal or construction purposes without checking:
GPS Accuracy Alert
Your phone's GPS can be off by 30 meters. This can cause critical errors in your data.
Check My Accuracy →Datum Shift Risk
Using the wrong coordinate system (e.g. WGS84 vs NAD83) creates a permanent 1-meter offset.
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