How can I get the geometry length in meters?

Question

The ST_length() function returns the length of a linestring but not in meters.

Is there a function like ST_Length() but in meters?.

Thanks!

Answer 1

St_Length() returns the length in the units of its Spatial Reference System. If you want to get meters, you will need to transform your feature to a different SRS that uses meters as units. This can be done on-the-fly, so don't worry about writing out another data set.

SELECT ST_AsText(ST_Transform(the_geom,26915)) from my_table;

In this example, SRID 26915 is UTM Zone 15 N, NAD83.

Answer 2

Examples of SQL request: how-to-calculate-length-of-polyline-geometry-for-several-tables-in-postgis

SQL request (length in km (/1000 -delete for meters)):

SELECT 
sum(ST_Length_Spheroid(the_geom,'SPHEROID["WGS 84",6378137,298.257223563]'))/1000 AS km_roads 
FROM 
"D1_r";