Convert coordinates from Merchich (EPSG:4261) to WGS 84 (EPSG:4326) — official EPSG transformation parameters, accuracy and area of use, with a free in-browser converter.
Merchich (EPSG:4261) is Morocco's classical datum on the Clarke 1880 (IGN) ellipsoid, with its origin at the Merchich observatory near Casablanca. Moroccan mapping is typically published in the Lambert conformal zones based on it — Maroc Nord and Maroc Sud (EPSG:26191, 26192).
The published EPSG transformation to WGS 84 is a geocentric translation accurate to several metres. For most map-integration purposes that is sufficient; geodetic work in Morocco now uses ITRF-based reference frames.
If your source data is in Lambert Maroc coordinates, unproject from the correct zone first — Nord and Sud overlap in places, and mixing them produces kilometre-scale errors.
Try it: Casablanca, Morocco
Input (EPSG:4261): -7.5898, 33.5731
The EPSG Geodetic Parameter Dataset defines 1 transformation between Merchich (EPSG:4261) and WGS 84 (EPSG:4326). Its parameters, accuracy and area of use are listed below.
| Parameter | Value | Unit |
|---|---|---|
| X-axis translation(tx) | 31 | metre |
| Y-axis translation(ty) | 146 | metre |
| Z-axis translation(tz) | 47 | metre |
Derived at 9 stations. Accuracy 5m, 3m and 3m in X, Y and Z axes.
The same transformation with common GIS tools and libraries:
from pyproj import Transformer
transformer = Transformer.from_crs("EPSG:4261", "EPSG:4326", always_xy=True)
x, y = transformer.transform(-73.9857, 40.7484)
print(x, y)geographic system using latitude and longitude on an ellipsoid · Area of use: Africa - Morocco and Western Sahara - onshore
+proj=longlat +ellps=clrk80ign +no_defs +type=crsMore about EPSG:4261 →
geographic system using latitude and longitude on an ellipsoid · Area of use: World (by country)
+proj=longlat +datum=WGS84 +no_defs +type=crsMore about EPSG:4326 →