A very limited number of LDA approaches also incorporate  a glideslope. These are annotated in the plan view of the  instrument approach chart with a note, “LDA/Glideslope.”  These procedures fall under a newly defined category of  approaches called Approach (Procedure) with Vertical  Guidance (aviation) APVs. LDA minima for with and without  glideslope is provided and annotated on the minima lines  of the approach chart as S−LDA/GS and S−LDA. Because  the final approach course is not aligned with the runway  centerline, additional maneuvering is required compared  to an ILS approach. [Figure 4-61]  The SDF provides a final approach course similar to that of  the ILS localizer. It does not provide glideslope information.  A clear understanding of the ILS localizer and the additional  factors listed below completely describe the operational  characteristics and use of the SDF. [Figure 4-62]  The approach techniques and procedures used in an SDF  instrument approach are essentially the same as those  employed in executing a standard localizer approach  except the SDF course may not be aligned with the runway  and the course may be wider, resulting in less precision.  Like the LOC type approaches, the SDF is an alternative  approach that may be installed at an airport for a variety  of reasons, including terrain. The final approach is provided  a minimum of 250 feet obstacle clearance for straight-in  approaches while in the final approach area, which is an  area defined for a 6° course: 1,000 feet at or abeam the  runway threshold expanding to 19,228 feet (10 NM) from  the threshold. The same final approach area for a 12°  course is larger. This type of approach is also designed with  a maximum descent gradient of 400 feet per NM, unless  circling only minimums are authorized.  Simplified Directional Facility (SDF)  4-78 