Updated towgs84 parameters of geographic JTSK CRS, the towgs84 values were calculated for area of Czech and Slovak Republic as it is described here: http://grass.fsv.cvut.cz/gwiki/%C4%8Ceskoslovensk%C3%BD_transforma%C4%8Dn%C3%AD_kl%C3%AD%C4%8D

UPDATE tbl_srs set parameters = '+proj=longlat +ellps=bessel +towgs84=542.5,89.2,456.9,5.517,2.275,5.516,6.96  +no_defs' WHERE auth_id = '4156';

UPDATE tbl_srs set parameters = '+proj=longlat +ellps=bessel +towgs84=542.5,89.2,456.9,5.517,2.275,5.516,6.96 +pm=ferro +no_defs' WHERE auth_id = '4818';