Skip to content
transform

Convert NTF to RGF93 v1

Convert coordinates from NTF (EPSG:4275) to RGF93 v1 (EPSG:4171) — official EPSG transformation parameters, accuracy and area of use, with a free in-browser converter.

Direct link to this transformation: epsgtransform.com/transform/epsg-4275-to-epsg-4171

Official EPSG transformation from NTF to RGF93 v1

The EPSG Geodetic Parameter Dataset defines 1 transformation between NTF (EPSG:4275) and RGF93 v1 (EPSG:4171). Its parameters, accuracy and area of use are listed below.

NTF to RGF93 v1 (1)

EPSG:9327±1 m
Method:
Geocentric translations (geog2D domain) by grid (IGN)
Area of use:
France - onshore - mainland and Corsica
Scope:
Transformation of coordinates at 1m level of accuracy.

Grid file: gr3df97a.txt

May be emulated using NTv2 method - see tfm code 15958. Also used to transform between NTF and later realizations of RGF93.

Convert EPSG:4275 to EPSG:4171 in code

The same transformation with common GIS tools and libraries:

from pyproj import Transformer

transformer = Transformer.from_crs("EPSG:4275", "EPSG:4171", always_xy=True)
x, y = transformer.transform(-73.9857, 40.7484)
print(x, y)

Source: EPSG:4275 — NTF

geographic system using latitude and longitude on an ellipsoid · Area of use: France - onshore - mainland and Corsica

+proj=longlat +ellps=clrk80ign +towgs84=-168,-60,320,0,0,0,0 +no_defs +type=crs
More about EPSG:4275 →

Target: EPSG:4171 — RGF93 v1

geographic system using latitude and longitude on an ellipsoid · Area of use: France

+proj=longlat +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +no_defs +type=crs
More about EPSG:4171 →

Frequently asked questions

How accurate is converting NTF to RGF93 v1?
The most accurate official EPSG transformation between these systems is accurate to about ±1 m within its stated area of use. Browser-based converters approximate datum shifts with Helmert parameters; for surveying-grade work apply the official transformation (including the grid-shift files listed below) 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:4171 to EPSG:4275 →