In article ,
says...

G Farris wrote:


Look it up in any book, and you'll find probably a full paragraph,
indicating
the amount of printing ink the publishers wish to squander on this approach
-
the SDF (Simplified Directional Facility, IIRC) is like a LOC approach,
except
instead of being aligned with a friendly runway it's aligned with a big old
tree or communications antenna several degrees off the extended centerline.
Lateral precision is reduced, compared with a LOC, and MDA is
correspondingly
higher.


The above is the definition of an LDA.

Well, no. The LDA has the same characteristics as a localizer, but is not
aligned with the runway. The SDF has reduced lateral precision, and may not be
aligned with the runway.

G Faris