[postgis-users] Getting x km of a linestring expressed in projection (3857)

[Dave Potts]

I like to extra the first x km from a linestring geometry with an srid 
id of 3857, but I having problems working out how to do it.

I known its possible to split  a line using st_lineSubString, but that 
only works in fractions off a length,  I am interested in get it 
projection unit lengths, are there any better suggestions??

Dave.