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ILS-OAS 1

06.05.2015

Submission:

Anybody has how to derive the OAS surface equations? I mean since the software is not reliable and ICAO update process is taking longer than expected I would like to see if the formulas are somewhere to be able to recreate them.

Antonio Locandro - COCESNA - GIS Specialist - Honduras


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Answer or Commentary:

I.W.

Pans-Ops states:
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1.4.8.4.1 The OAS consist of six sloping plane surfaces (denoted by letters W, X, Y, and Z) arranged
symmetrically about the precision segment track, together with the horizontal plane which contains the threshold (see Figures II-1-1-8 and II-1-1-9). The geometry of the sloping surfaces is defined by four linear equations of the form z = Ax + By + C. In these equations x and y are position coordinates and z is the height of the surface at that position.
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The OAS constants A, B and C for each surface were previously tabulated in the "Green pages" of Pans-Ops. I am sure that there will be many other comments about these constants.

Who kept their "Green pages"  when ICAO said that they would not be needed any more??

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