WGS84 to BJ54 Converter
About WGS84 Coordinate System
WGS84 (World Geodetic System 1984) is the global standard geodetic reference system used by GPS. It defines an Earth-centered, Earth-fixed coordinate system and geodetic datum.
Developed by the U.S. Department of Defense in 1984, WGS84 has undergone several refinements (WGS84(G730), WGS84(G873), WGS84(G1150), WGS84(G1762)) to improve accuracy through GPS satellite observations.
WGS84 is the default coordinate system for GPS receivers worldwide. It is used in aviation, maritime navigation, Google Maps, OpenStreetMap, GIS applications, and scientific research.
WGS84 is the native coordinate system of the Global Positioning System (GPS), ensuring direct compatibility with all GPS receivers and satellite navigation systems worldwide.
As the most widely adopted geodetic datum, WGS84 provides a consistent global reference frame for mapping, surveying, and geospatial data exchange across international boundaries.
With continuous refinements, WGS84 achieves centimeter-level accuracy globally, making it suitable for high-precision applications like surveying, drone navigation, and scientific research.
About BJ54 Coordinate System
BJ54 (Beijing 1954 Coordinate System) was China's first national geodetic coordinate system.
BJ54 was established in 1954 based on the Soviet Pulkovo 1942 datum.
BJ54 was used for topographic mapping and infrastructure development in China from the 1950s through the 1990s.
BJ54 uses the Krasovsky 1940 ellipsoid, which differs from WGS84 by approximately 100-200 meters.
While largely superseded by CGCS2000, BJ54 coordinates exist in vast archives of historical maps.
WGS84 → BJ54 Conversion Guide
// WGS84 → BJ54 (7-parameter Helmert transformation)
// Step 1: Geodetic to Cartesian (WGS84)
N = a_WGS84 / √(1 - e²_WGS84 × sin²(φ))
X = (N + h) × cos(φ) × cos(λ)
Y = (N + h) × cos(φ) × sin(λ)
Z = (N × (1 - e²_WGS84) + h) × sin(φ)
// Step 2: Helmert 7-parameter transformation
X' = ΔX + (1 + s)(X + Rz·Y - Ry·Z)
Y' = ΔY + (1 + s)(-Rz·X + Y + Rx·Z)
Z' = ΔZ + (1 + s)(Ry·X - Rx·Y + Z)
// Step 3: Cartesian to Geodetic (Krasovsky 1940 ellipsoid)
// BJ54 uses Krasovsky 1940: a = 6378245.0, 1/f = 298.3WGS84 to BJ54 requires a full 7-parameter Helmert transformation because the two systems use different ellipsoids (WGS84 vs Krasovsky 1940) and different datum origins. The transformation involves converting to geocentric Cartesian coordinates, applying the Helmert transform, and converting back to geodetic coordinates using the target ellipsoid parameters.
- Enter WGS84 coordinates in decimal degrees format
- Input accurate 7-parameter values (dx, dy, dz, rx, ry, rz, s) for your specific region
- The tool performs Helmert transformation via geocentric Cartesian coordinates
- Output coordinates are in the BJ54 (Beijing 1954) system using Krasovsky 1940 ellipsoid
- 7-parameter values are region-specific and must be obtained from local surveying authorities
- The Krasovsky 1940 ellipsoid differs from WGS84 by approximately 100-200 meters
- Always verify BJ54 output coordinates against known local reference points