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Convert NAD27(CGQ77) to NAD83(CSRS)v2

Convert coordinates from NAD27(CGQ77) (EPSG:4609) to NAD83(CSRS)v2 (EPSG:8237) — official EPSG transformation parameters, accuracy and area of use, with a free in-browser converter.

Direct link to this transformation: epsgtransform.com/transform/epsg-4609-to-epsg-8237

Official EPSG transformation from NAD27(CGQ77) to NAD83(CSRS)v2

The EPSG Geodetic Parameter Dataset defines 1 transformation between NAD27(CGQ77) (EPSG:4609) and NAD83(CSRS)v2 (EPSG:8237). Its parameters, accuracy and area of use are listed below.

NAD27(CGQ77) to NAD83(CSRS)v2 (1)

EPSG:9240±1.5 m
Method:
NTv2
Area of use:
Canada - Quebec
Scope:
Transformation of coordinates at 1m to 2m level of accuracy.

Grid file: CGQ77-98.gsb

Also found with file name CQ77SCRS.GSB. Uses NT method which expects longitudes positive west; EPSG GeogCRSs NAD27(CGQ77) (code 4609) and NAD83(CSRS) (code 4617) have longitudes positive east.

Convert EPSG:4609 to EPSG:8237 in code

The same transformation with common GIS tools and libraries:

from pyproj import Transformer

transformer = Transformer.from_crs("EPSG:4609", "EPSG:8237", always_xy=True)
x, y = transformer.transform(-73.9857, 40.7484)
print(x, y)

Source: EPSG:4609 — NAD27(CGQ77)

geographic system using latitude and longitude on an ellipsoid · Area of use: Canada - Quebec

+proj=longlat +ellps=clrk66 +no_defs +type=crs
More about EPSG:4609 →

Target: EPSG:8237 — NAD83(CSRS)v2

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

+proj=longlat +ellps=GRS80 +no_defs +type=crs
More about EPSG:8237 →

Frequently asked questions

How accurate is converting NAD27(CGQ77) to NAD83(CSRS)v2?
The most accurate official EPSG transformation between these systems is accurate to about ±1.5 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:8237 to EPSG:4609 →