Publication: Magyar Közlöny
Issue: MK-2007-70 (Year: 2007, Number: 70)
Era: 2004-2010
Section: Melléklet a 2007. évi XLVI. törvényhez
Paragraph Index: 4436

e) Finally, limit the values of XZi and YZi to fit in the 17-bit or 14-bit field allotted to each coordinate: For airborne encoding: YZi = MOD(YZi, 217), XZi = MOD(XZi, 217) For surface encoding: YZi = MOD(YZi, 217), XZi = MOD(XZi, 217) For TCP, TCP+1 encoding: YZ0 = MOD(YZ0, 214), XZ0 = MOD(XZ0, 214) 2.6.4 LOCALLY UNAMBIGUOUS CPR DECODING The CPR algorithm shall decode a geographic position (latitude, Rlati, and longitude, Rloni,) that is locally unambiguous with respect to a reference point (lats, lons) known to be within 180 NM of the true airborne position (or within 45 NM for a surface message). 219 MOD lat ∆lati , ( ) ∆lati ---------------------------------------- 2-- + ⋅     214 MOD lat ∆lat0 , ( ) ∆lati ----------------------------------------- 2-- + ⋅     YZi ------- floor lat ∆lati -----------     +     YZi ------- floor lat ∆lati -----------     +     YZi ------- floor lat ∆lat0 ------------     +     ∆loni 360° NL Rlati ( ) i – --------------------------------- when NL Rlati ( ) i > – 360°, when NL Rlati ( ) i – =        = 217 MOD lon ∆loni , ( ) ∆loni ------------------------------------------- 2-- + ⋅     219 MOD lon ∆loni , ( ) ∆loni ------------------------------------------- 2-- + ⋅     214 MOD lon ∆lon0 , ( ) ∆lon0 -------------------------------------------- 2-- + ⋅     2007/70/II. szám Part I Annex 10 — Aeronautical Telecommunications 5-91 28/11/02 No. 77 Note.— This reference point may be a previously tracked position that has been confirmed by global decoding (see 2.6.7) or it may be the own-aircraft position, which would be used for decoding a new tentative position report. The encoded position coordinates XZi and YZi and the CPR encoding type i (0 for the even encoding and 1 for the odd encoding) contained in a Mode S extended squitter message shall be decoded by performing the sequence of computations given in 2.6.5 for the airborne and TCP, TCP+1 format types and in 2.6.6 for the surface format type. 2.6.5 COMPUTATIONS FOR THE AIRBORNE MESSAGE AND TCP, TCP+1 MESSAGE The following computations shall be performed to obtain the decoded latitude/longitude for the airborne and TCP, TCP+1 message formats. For the TCP, TCP+1 format, i shall always be set to 0 (even encoding), whereas the airborne format shall use both even (i = 0) and odd (i = 1) encoding. For the airborne format, Nb shall equal 17, and for the TCP, TCP+1 format, Nb shall equal 14.

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