Xian80 to WGS84 Converter
About Xian80 Coordinate System
Xi'an 80 (Xian1980, Chinese Geodetic Datum 1980) is a Chinese national geodetic datum established in the 1980s. It uses the IAG75 ellipsoid (a=6378140m, 1/f=298.257) and employs a 7-parameter Helmert transformation from WGS84. It is widely used in Chinese surveying and mapping alongside BJ54 and CGCS2000.
Xi'an 80 was established in the 1980s as China's second national geodetic datum, replacing the earlier BJ54 system. It improved accuracy by using the IAG75 ellipsoid and a more precise geoid model, providing a unified reference for national mapping and infrastructure projects.
Xi'an 80 is widely used in Chinese surveying, mapping, and GIS applications, particularly in legacy data and regional projects. While CGCS2000 is the modern standard, large volumes of spatial data remain in Xi'an 80 and conversion between these systems is commonly required.
Xi'an 80 is an official Chinese national geodetic datum, used extensively in legacy surveying, mapping, and infrastructure data.
Xi'an 80 uses the IAG75 ellipsoid (a=6378140m, 1/f=298.257), the same as the IUGG 1975/IAU 1976 recommended values.
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.
⚙️ 7-Parameter Helmert Transformation Guide
The 7-parameter Helmert transformation (also known as the time-tested similarity transformation / 3D conformal transformation) is the standard geodetic method for converting coordinates between two different datums. It applies three translations (dx, dy, dz), three rotations (rx, ry, rz), and one scale factor (s) to transform coordinates from one reference frame to another. This method preserves shapes (conformal) while shifting and rotating the entire coordinate system in 3D space.
Xian80 uses a different ellipsoid and reference frame than WGS84. To bridge this difference, a 7-parameter transformation is required. Unlike simpler methods such as geocentric translation (3-parameter) or Molodensky transformation, the 7-parameter Helmert provides the highest accuracy by accounting for all spatial differences between the two datums, including axis rotations and scale variations. The parameters must be sourced from local surveying authorities or geodetic organizations.
Translation Parameters
dx, dy, dz (meters) - shifts along X, Y, Z axes of the Earth-centered reference frame
Rotation Parameters
rx, ry, rz (radians) - rotations around each axis to align datum orientations
Scale Parameter
s (ppm) - scale factor adjusting for size differences between ellipsoids
# Example parameters for Xian80 to WGS84 # These are REGIONAL approximations — use official values for precise work. dx = 0 # X-axis shift (meters) dy = 0 # Y-axis shift (meters) dz = 0 # Z-axis shift (meters) rx = 0 # X-axis rotation (arcseconds) ry = 0 # Y-axis rotation (arcseconds) rz = 0 # Z-axis rotation (arcseconds) s = 0 # Scale factor (ppm) # 💡 For Xian80 → WGS84, enter the 7 parameters # provided by your national surveying authority for the most accurate results.
⚠️ Important: 7-parameter values are region-dependent. Using parameters from a different region than your coordinate data will result in increased positional errors. Always obtain official parameters from your local surveying authority (e.g., NGII for Korea, Geoscience Australia, Ordnance Survey for UK, etc.).
Xian80 to WGS84 Conversion Guide
// Xian80 → WGS84 (7-parameter Helmert transformation)
// Between WGS84 ellipsoid and IAG75 ellipsoid
// Step 1: Convert from IAG75 to geocentric Cartesian
// Using source ellipsoid: a = 6378140.0, 1/f = 298.257
N = a_source / √(1 - e²_source × sin²(φ))
X = (N + h) × cos(φ) × cos(λ)
Y = (N + h) × cos(φ) × sin(λ)
Z = (N × (1 - e²_source) + h) × sin(φ)
// Step 2: Helmert 7-parameter transform (Xian80 → WGS84)
// Parameters: dx, dy, dz (m), rx, ry, rz (rad), s (ppm)
// Reverse sign for inverse 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: Convert back to geodetic using WGS84 ellipsoid
// a = 6378137.0, 1/f = 298.257223563
p = √(X'² + Y'²)
θ = atan2(Z' × a_target, p × (1 - f_target))
φ' = atan2(Z' + e²_target × (1 - f_target) × a_target × sin³(θ),
p - e²_target × a_target × cos³(θ))
λ' = atan2(Y', X')Xian80 to WGS84 requires a full 7-parameter Helmert transformation because the two systems use different ellipsoids and different datum origins. The conversion accuracy depends on the quality of regional 7-parameter values used.
- Enter your Xian80 coordinates in the input field (latitude, longitude, one pair per line)
- Click the Convert button to transform coordinates from Xian80 to WGS84
- Review the converted WGS84 coordinates in the output field
- Copy the results or save them as an XLSX file for further use
- Ensure coordinates are within valid ranges before conversion
- For batch conversions, enter one coordinate pair per line
- Verify a sample of converted coordinates on your target platform
- All conversions are performed client-side for complete data privacy