Convert ITRF90 to ITRF91

Convert coordinates from ITRF90 (EPSG:4912) to ITRF91 (EPSG:4913) — official EPSG transformation parameters, accuracy and area of use, with a free in-browser converter.

From

Input (x, y)

Output (x, y)

Direct link to this transformation: epsgtransform.com/transform/epsg-4912-to-epsg-4913

Official EPSG transformations from ITRF90 to ITRF91

The EPSG Geodetic Parameter Dataset defines 2 transformations between ITRF90 (EPSG:4912) and ITRF91 (EPSG:4913). Each applies to a specific area — pick the one whose area of use covers your data.

ITRF90 to ITRF91 (1)

EPSG:9022±0.007 mBest accuracy

Method:: Position Vector transformation (geocentric domain)
Area of use:: World
Scope:: Geodesy.

Parameter	Value	Unit
X-axis translation(tx)	-0.1	centimetre
Y-axis translation(ty)	0.4	centimetre
Z-axis translation(tz)	1.6	centimetre
X-axis rotation(rx)	0	milliarc-second
Y-axis rotation(ry)	0	milliarc-second
Z-axis rotation(rz)	0	milliarc-second
Scale difference(ds)	-0.3	parts per billion

Scale difference in ppb and scale difference rate in ppb/yr where 1/billion = 1E-9 or nm/m. Superseded by parameter values derived from transformations to ITRF2020 (change in tX), see EPSG:10141.

ITRF90 to ITRF91 (2)

EPSG:10141±0.007 m

Method:: Position Vector transformation (geocentric domain)
Area of use:: World
Scope:: Geodesy.

Parameter	Value	Unit
X-axis translation(tx)	0.2	centimetre
Y-axis translation(ty)	0.4	centimetre
Z-axis translation(tz)	1.6	centimetre
X-axis rotation(rx)	0	milliarc-second
Y-axis rotation(ry)	0	milliarc-second
Z-axis rotation(rz)	0	milliarc-second
Scale difference(ds)	-0.3	parts per billion

Parameter values derived from differences in CTs to ITRF2020 (codes 10100 and 10103). These supersede all values published in past IERS/ITRF documentation (CT code 9022). Scale difference in ppb and scale difference rate in ppb/yr where 1/billion = 1E-9.

Convert EPSG:4912 to EPSG:4913 in code

The same transformation with common GIS tools and libraries:

from pyproj import Transformer

transformer = Transformer.from_crs("EPSG:4912", "EPSG:4913", always_xy=True)
x, y = transformer.transform(-73.9857, 40.7484)
print(x, y)

Source: EPSG:4912 — ITRF90

geocentric Cartesian system (Earth-centred Earth-fixed) · Area of use: World

+proj=geocent +ellps=GRS80 +units=m +no_defs +type=crs

More about EPSG:4912 →

Target: EPSG:4913 — ITRF91

geocentric Cartesian system (Earth-centred Earth-fixed) · Area of use: World

+proj=geocent +ellps=GRS80 +units=m +no_defs +type=crs

More about EPSG:4913 →

Frequently asked questions

How accurate is converting ITRF90 to ITRF91?: The most accurate official EPSG transformation between these systems is accurate to about ±0.007 m within its stated area of use. Browser-based converters approximate datum shifts with Helmert parameters; for surveying-grade work apply the official transformation in a desktop GIS.
Does my data leave the browser when I use this converter?: No. All coordinate transformations are computed locally in your browser using proj4js. The coordinates you enter are never transmitted to any server.

Need the reverse? Convert EPSG:4913 to EPSG:4912 →