3D software-6

25.10.2004

Submission:

I believe the following items should be clarified in 8168 text for the reasons identified by Mr. Whitworth:

Secondary area surfaces seem to be plane surfaces on page 3-3 (fig. III-1-1). On page 3-30 (fig. III-5-2) it states that factor "D" is the "distance of the obstacle from edge of primary area" (this may induce in error, as correctly identified by Mr. Whitworth)

Nevertheless what's important here is the distance of the obstacle from the aircraft (perpendicular to nominal track when aircraft is abeam the obstacle which is in accordance with fig III-5-1.). I believe Mr. Obrad Puskarica has been very clear in his opinion and I fully agree with him. One important point identified by Mr. O. Puskarica is the fact that the secondary area surface (being discussed here) is indeed a curved surface. This is important since some 3D software do not create true curved surfaces (unless an appropriate add-on has been loaded). The consequence here is that the 3D software may not show penetration of an obstacle because it is not able to draw the surface fully in accordance with the applicable criteria.

Henrique Nunes - Atc/Pans-Ops Officer

Santa Maria Oceanic ACC - Portugal