Extensions
Scalar Functions
Returns the length of the input geometry in meters, using a ellipsoidal model of the earth  
The input geometry is assumed to be in the [EPSG:4326](https://en.wikipedia.org/wiki/World_Geodetic_System) coordinate system (WGS84), with [latitude, longitude] axis order and the length is returned in square meters. This function uses the [GeographicLib](https://geographiclib.sourceforge.io/) library, calculating the length using an ellipsoidal model of the earth. This is a highly accurate method for calculating the length of a line geometry taking the curvature of the earth into account, but is also the slowest.  
Returns `0.0` for any geometry that is not a `LINESTRING`, `MULTILINESTRING` or `GEOMETRYCOLLECTION` containing line geometries.  
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#### ST_LineMerge {#docs:extensions:spatial:functions::st_linemerge}