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Convert NTF (Paris) to RGF93 v1

Convert coordinates from NTF (Paris) (EPSG:4807) 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-4807-to-epsg-4171

Official EPSG transformations from NTF (Paris) to RGF93 v1

The EPSG Geodetic Parameter Dataset defines 2 transformations between NTF (Paris) (EPSG:4807) and RGF93 v1 (EPSG:4171). Each applies to a specific area — pick the one whose area of use covers your data.

NTF (Paris) to RGF93 v1 (2)

EPSG:7811±1 mBest accuracy
Method:
Concatenated operation
Area of use:
France - onshore - mainland and Corsica
Scope:
Transformation of coordinates at 1m level of accuracy.
  1. NTF (Paris) to NTF (1) (null)
  2. RGF93 v1 to NTF (2) (null)

Second step is an emulation (using the NTv2 method) of the geocentric interpolation method described in CT code 9337. Note that the grid file parameters are of opposite sign.

NTF (Paris) to RGF93 v1 (1)

EPSG:9337±1 m
Method:
Concatenated operation
Area of use:
France - onshore - mainland and Corsica
Scope:
Transformation of coordinates at 1m level of accuracy.
  1. NTF (Paris) to NTF (1) (null)
  2. NTF to RGF93 v1 (1) (null)

See transformation code 7811 for an alternative which uses the NTv2 method as an emulation of the geocentric interpolation in the second step.

Convert EPSG:4807 to EPSG:4171 in code

The same transformation with common GIS tools and libraries:

from pyproj import Transformer

transformer = Transformer.from_crs("EPSG:4807", "EPSG:4171", always_xy=True)
x, y = transformer.transform(-73.9857, 40.7484)
print(x, y)

Source: EPSG:4807 — NTF (Paris)

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

+proj=longlat +ellps=clrk80ign +pm=paris +towgs84=-168,-60,320,0,0,0,0 +no_defs +type=crs
More about EPSG:4807 →

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 (Paris) 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 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:4807 →