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    EPSG reference

    EPSG:30491 — Voirol 1875 / Nord Algerie (ancienne)

    Voirol 1875 / Nord Algerie (ancienne) (EPSG:30491) — a Projected (metres) system on the clrk80ign datum, used in Algeria. Parameters, proj4, WKT, accuracy ±0.1 m, plus a…

    At a glance

    EPSG
    30491
    Name
    Voirol 1875 / Nord Algerie (ancienne)
    Kind
    Projected (metres)
    Family
    Lambert Conformal Conic
    Ellipsoid
    clrk80ign
    Accuracy
    ±0.1 m (vs PROJ)
    Countries
    Algeria
    Convert from this system now

    Area of use

    West-2.22°
    South34.64°
    East8.64°
    North37.14°

    Projection parameters

    Projectionlcc
    Standard parallel 136
    Latitude of origin36
    Central meridian2.7
    Scale factor0.999625544
    False easting500000
    False northing300000
    Ellipsoidclrk80ign
    Unitsm
    Helmert shift to WGS84-73,-247,227,0,0,0,0
    proj4
    +proj=lcc +lat_1=36 +lat_0=36 +lon_0=2.7 +k_0=0.999625544 +x_0=500000 +y_0=300000 +ellps=clrk80ign +units=m +no_defs +towgs84=-73,-247,227,0,0,0,0
    WKT (ESRI)
    PROJCS["Voirol 1875 / Nord Algerie (ancienne)",GEOGCS["GCS_Voirol 1875 / Nord Algerie (ancienne)",DATUM["D_Clarke_1880_IGN",SPHEROID["Clarke_1880_IGN",6378249.2,293.4660212936269],TOWGS84[-73,-247,227,0,0,0,0]],PRIMEM["Greenwich",0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["False_Easting",500000],PARAMETER["False_Northing",300000],PARAMETER["Central_Meridian",2.7],PARAMETER["Standard_Parallel_1",36],PARAMETER["Scale_Factor",0.999625544],PARAMETER["Latitude_Of_Origin",36],UNIT["Meter",1],AUTHORITY["EPSG","30491"]]

    Sample conversion

    Algeria capital: WGS84 3.05880, 36.75380 → EPSG:30491 532274.263, 383775.619

    Values are within ±0.1 m at the test point.

    About the Lambert Conformal Conic family

    Voirol 1875 / Nord Algerie (ancienne) uses the Lambert Conformal Conic projection — a cone-based, angle-preserving grid well suited to territories that stretch east–west, defined by one or two standard parallels. It is common for national mapping and for oil-and-gas grids across North Africa and Arabia.

    Scale is true along the standard parallel(s) and grows away from them; for precise distance work reduce ground distances to grid using the point scale factor. Confirm both standard parallels and the datum before trusting imported coordinates.

    Related systems

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    FAQ

    What is EPSG:30491?
    It is the coordinate system “Voirol 1875 / Nord Algerie (ancienne)”, a Projected (metres) system in the Lambert Conformal Conic family, identified worldwide by the code EPSG:30491.
    What datum does it use, and how accurate is it?
    It is based on the clrk80ign ellipsoid and it carries Helmert parameters to WGS84. The residual at the test point is about ±0.1 m versus PROJ; for centimetre work use a geodetic adjustment service.
    Where is this system used?
    It is used in Algeria. This page shows its area of use as a coordinate rectangle above.
    How do I convert EPSG:30491 to WGS84?
    Use the free coordinate converter above (preloaded with this system) to convert to WGS84, UTM, or any other system, within a ±0.1 m residual.

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