EPSG Library · North Africa

EPSG:4261 — Merchich

Source: EPSG Dataset via PROJ 9.5.1 · Updated 2026-10-05

Summary

EPSG:4261 (Merchich) is a geographic 2D coordinate reference system on the Merchich datum with coordinates in degrees. Area of use: Africa - Morocco and Western Sahara - onshore.

Type: geographic 2D
Datum: Merchich
Units: degree
Axes: Lat, Lon

Definition

EPSG:4261 as published in the EPSG Dataset (PROJ 9.5.1).
Property	Value
EPSG code	EPSG:4261
Name	Merchich
Type	Geographic 2d CRS
Datum	Merchich
Ellipsoid	Clarke 1880 (IGN) (a = 6,378,249.200 m, 1/f = 293.466021)
Prime meridian	Greenwich
Axes	Geodetic latitude (Lat, north, degree); Geodetic longitude (Lon, east, degree)
Scope	Geodesy.
Bounding box	-17.16° to -1.01° longitude, 20.71° to 35.97° latitude

Area of use

Africa - Morocco and Western Sahara - onshore.

Example coordinates

A WGS 84 point at longitude -9.085°, latitude 28.34° (inside the area of use) has these coordinates in EPSG:4261:

Computed with PROJ using the EPSG default operation: unavailable until proj_trans is called.
Axis	Value	Unit
Longitude	-9.086520	°
Latitude	28.342290	°

Open this conversion in the coordinate converter

Transformations to WGS 84

Candidate operations from the EPSG Dataset, best first as ranked by PROJ.
Operation	Accuracy	Area of use
axis order change (2D) + Merchich to WGS 84 (1) + axis order change (2D)	7 m	Morocco - onshore.

Transformations change the datum, so each has an accuracy and an area of use. Choose the most accurate one that covers your data and record its name. See datum transformations.

Definitions and downloads

PROJ string

+proj=longlat +ellps=clrk80ign +no_defs +type=crs

A PROJ string cannot carry every EPSG detail (axis order, datum ensemble, transformations). Prefer WKT2 or the EPSG code itself.

Proj4js definition used by the converter

+proj=longlat +ellps=clrk80ign +towgs84=31,146,47 +no_defs

Datum shift from Merchich to WGS 84 (1) (EPSG accuracy 7 m), the best single Helmert operation for this area of use. Where PROJ prefers a grid-based or multi-step operation (see the table above), results can differ by up to that operation's accuracy.

WKT2:2019

GEOGCRS["Merchich", DATUM["Merchich", ELLIPSOID["Clarke 1880 (IGN)",6378249.2,293.466021293627, LENGTHUNIT["metre",1]]], PRIMEM["Greenwich",0, ANGLEUNIT["degree",0.0174532925199433]], CS[ellipsoidal,2], AXIS["geodetic latitude (Lat)",north, ORDER[1], ANGLEUNIT["degree",0.0174532925199433]], AXIS["geodetic longitude (Lon)",east, ORDER[2], ANGLEUNIT["degree",0.0174532925199433]], USAGE[ SCOPE["Geodesy."], AREA["Africa - Morocco and Western Sahara - onshore."], BBOX[20.71,-17.16,35.97,-1.01]], ID["EPSG",4261]]

Downloads

4261.prj — ESRI WKT for shapefiles
4261.wkt — OGC WKT2:2019

FAQ

What is EPSG:4261?

EPSG:4261 (Merchich) is a geographic 2D coordinate reference system on the Merchich datum with coordinates in degrees. Area of use: Africa - Morocco and Western Sahara - onshore.

Where can EPSG:4261 be used?

Its area of use is: Africa - Morocco and Western Sahara - onshore.

What is the axis order of EPSG:4261?

By the EPSG definition: Geodetic latitude, Geodetic longitude. Many GIS formats such as GeoJSON and KML store longitude first instead.

How accurate is the transformation from EPSG:4261 to WGS 84?

The most accurate EPSG transformation listed here is “axis order change (2D) + Merchich to WGS 84 (1) + axis order change (2D)”, with a stated accuracy of 7 m for Morocco - onshore.. Always check the area of use before applying it.

Coordinate systems

Articles

Tools

References

IOGP. EPSG Geodetic Parameter Dataset, epsg.org/crs_4261.
PROJ 9.5.1 / pyproj 3.7.2, used to compute every value on this page.

Cite this page

GeoCAD Bridge. “EPSG:4261 — Merchich.” GeoCAD Bridge EPSG Library, updated 2026-10-05. https://www.geocadbridge.com/epsg/4261/