sebulba wrote on Dec 8^th, 2013 at 3:58am:

Good Morning All - Can any members explain how Lat & Long coordinates are computed for the 757 in FSX - take the ROKU1G STAR for EGNX airport (based on the latest AIRAC cycle). Waypoint ROKUP is described in the STAR db file as 53.017222; -1.515833 yet the actual Lat/Long according to EAG data is N53 01.0 W001 31.0 _ I'm trying to add the respective files for VHHX according to the section of the FMC manual but need to figure out how these coordinates are obtained in the db(s)...Many thanks ::)

You could just add Longitude and Latitude coordinates directly into the FMC without modifying the AIRAC files if you wanted to.
Why not add them in how you think they are deed, then test them. Or see if you can get the info from the Navigraph forum.