United Kingdom Geodetic Authority

Detailed technical analysis of the OSTN15 transformation and the British National Grid.

Technical Specification Overview

ParameterStandard Value
Primary Geodetic DatumETRS89
Legacy/Historical DatumOSGB36
Local Grid ProjectionBritish National Grid
Known Datum Shift (vs WGS84)100 - 130 meters
National Mapping AuthorityOrdnance Survey (OS)

Professional Compliance Warning

Failure to apply correct transformation parameters when converting from WGS84 (GPS) to ETRS89 creates a systematic 100 - 130 meters offset. In construction and legal surveying, this drift exceeds the allowable error margin for any certified geodetic workflow.

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NAD83 (2011) analysis.

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ETRS89 analysis.

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