ECEF to local ENU converter

Enter the target ECEF coordinates and the reference point's geodetic latitude, longitude, and optional ellipsoidal height. The calculator derives the origin's ECEF position on WGS 84, subtracts it from the target, and rotates the resulting vector into the local tangent frame. You can also supply another ellipsoid and choose the output precision.

Define the ECEF point and local origin consistently

An ECEF coordinate describes a position in a Cartesian frame fixed to the rotating Earth. The X axis passes through latitude zero and longitude zero, the Y axis passes through latitude zero and longitude 90 degrees east, and the Z axis points through the North Pole. Supply all three target coordinates in meters. The local frame also needs an origin, given here as geodetic latitude, longitude, and ellipsoidal height. Latitude and longitude are expressed in decimal degrees, while height is measured along the ellipsoid normal rather than above mean sea level. That distinction matters: an orthometric elevation from a map is not automatically an ellipsoidal height, because the geoid and reference ellipsoid differ. Keep the target ECEF coordinate and the origin tied to the same datum. The defaults use the WGS 84 semi-major axis and inverse flattening, which is appropriate for ordinary GNSS coordinates. If your source uses a regional datum or another reference ellipsoid, enter its matching parameters before interpreting the local displacement.

Understand the east, north, and up rotation

The conversion has two deterministic stages. First, the calculator converts the reference geodetic position to ECEF using the selected ellipsoid and subtracts that origin from the target XYZ position. This produces a displacement vector, not another absolute position. Second, it rotates the displacement using the reference latitude and longitude. East is tangent to the latitude circle and positive toward increasing longitude. North is tangent to the meridian and positive toward increasing geodetic latitude. Up is normal to the reference ellipsoid and positive away from it. The three returned values are therefore signed distances in meters. A negative east value means west of the local origin, a negative north value means south, and a negative up value means below the origin's tangent plane. ENU is a local linear frame, so its components are especially intuitive over limited areas. Over long distances, up can differ substantially from a simple height difference because Earth curvature changes the orientation of local vertical.

Use the result in positioning and engineering workflows

Local ENU coordinates are convenient when an application needs relative motion or geometry instead of planet-scale XYZ numbers. Surveying software can express observations around a station, robotics systems can place detections in a map centered on a base, and GNSS analysis can compare a measured antenna position with a known reference. Choose the origin deliberately and retain its latitude, longitude, height, ellipsoid, and datum with the result; without that metadata, an ENU tuple cannot be reconstructed as a global position. The decimals option controls presentation rounding from zero through twelve places, while all calculations use JavaScript floating-point arithmetic before rounding. Increasing decimals does not create accuracy that was absent from the inputs. For quality control, convert the exact ECEF coordinates of the reference origin and confirm that east, north, and up are all zero within the requested precision. Also test a known offset near the origin and verify the expected signs. The calculation is pure, performs no network requests, and returns the same output for the same input.