Get sum of change in degrees between the 2 line segments in every trigram of points in a LinestringZ as proxy for curvature.

PostGIS_LinestringZ_Curvature.sql

select
ogc_fid,
sum(degrees(atan2(opposite, adjacent))) as delta_degrees
from
    (select
    ogc_fid,
    point_idx,
    st_3ddistance(unit_tangent_endpoint, unit_vector_endpoint) as opposite,
    st_3ddistance(common_point, unit_vector_endpoint) as adjacent
    from
        (select
        ogc_fid,
        point_idx,
        point_2 as common_point,
        st_setsrid(
        st_makepoint(
        st_x(point_2) + ((st_x(point_2) - st_x(point_1)) / st_3ddistance(point_1, point_2)),
        st_y(point_2) + ((st_y(point_2) - st_y(point_1)) / st_3ddistance(point_1, point_2)),
        st_z(point_2) + ((st_z(point_2) - st_z(point_1)) / st_3ddistance(point_1, point_2))
        ), 2852
        ) as unit_tangent_endpoint,
        st_setsrid(
        st_makepoint(
        st_x(point_2) + ((st_x(point_3) - st_x(point_2)) / st_3ddistance(point_2, point_3)),
        st_y(point_2) + ((st_y(point_3) - st_y(point_2)) / st_3ddistance(point_2, point_3)),
        st_z(point_2) + ((st_z(point_3) - st_z(point_3)) / st_3ddistance(point_2, point_3))
        ), 2852
        ) as unit_vector_endpoint
        from
            (select ogc_fid, point_idx, point_count,
            st_transform(st_pointn(geom, point_idx), 2852) as point_1,
            st_transform(st_pointn(geom, point_idx+1), 2852) as point_2,
            st_transform(st_pointn(geom, point_idx+2), 2852) as point_3
            from
                (select ogc_fid, st_numpoints(wkb_geometry) as point_count,
                generate_series(1, st_numpoints(wkb_geometry)-2) as point_idx, wkb_geometry as geom
                from vermont.roads
                where
                tnmfrc < 4
                and st_numpoints(wkb_geometry) >= 3
                ) as points
            ) as point_3tuple
        where st_3ddistance(point_1, point_2) > 0 and st_3ddistance(point_2, point_3) > 0
    ) as unit_vector_endpoints
) as tan_components
group by ogc_fid