Publication: Magyar Közlöny
Issue: MK-2007-70 (Year: 2007, Number: 70)
Era: 2004-2010
Section: Melléklet a 2007. évi XLVI. törvényhez
Paragraph Index: 4453

g) Compute the global longitude, Rlon0 or Rlon1, according to whether the most recently received airborne position message was encoded using the even format (that is, with i = 0) or the odd format (i = 1): Rloni = ∆loni ⋅ where ni = greater of [NL(Rlati) – i] and 1. 2.6.8 CPR DECODING OF RECEIVED POSITION REPORTS 2.6.8.1 OVERVIEW The techniques described in the preceding paragraphs (locally and globally unambiguous decoding) shall be used together to decode the latitude/longitude contained in airborne, surface, and TCP or TCP+1 position reports. The process shall begin with globally unambiguous decoding based upon the receipt of an even and an odd encoded position squitter. Once the globally unambiguous position is determined, either of two approaches shall be used to support subsequent decoding based upon a single position report, either even or odd encoding. The two techniques shall be range monitoring and emitter centered local decoding. j floor 59 YZ0 60 YZ1 ⋅ – ⋅ --------------------------------------------- 2-- +     = MOD j 60 i – , ( ) YZi ------- +     ∆loni 360° ni -----------, = m floor XZ0 NL – ( ) XZ1 NL ⋅ – ⋅ --------------------------------------------------------------- 2-- +    , = MOD m ni , ( ) YZi ------- +    , 2007/70/II. szám Annex 10 — Aeronautical Telecommunications Volume III 5-94 28/11/02 No. 77 2.6.8.2 RANGE MONITORING LOCAL DECODING 2.6.8.2.1 Range monitoring technique In this approach, local decoding for the airborne format (2.6.4) shall be performed based upon the current position of the receiver. This shall provide the position of a transmitting aircraft that is unambiguous to plus or minus 180 NM. Note 1.— If the transmitting aircraft is within 180 NM, the local decoding technique will correctly decode the location of the aircraft. The range of the transmitting aircraft shall be checked at detection and tracks shall only be initiated if the range is less than 180 NM. Once initiated, the range of the tracked aircraft shall be checked at each update and the track shall be dropped if the range becomes equal to or greater than 180 NM. For the surface format, the same process shall be used except that the transmitting aircraft must be within 45 NM for detection and tracking. Note 2.— The range limits are reduced since the ambiguity limit for the surface position reports is one-fourth that of the airborne case. 2.6.8.2.2 Range monitoring example 2.6.8.2.2.1 Decoding of airborne position 2.6.8.2.2.1.1 Detection. At detection, a globally unambiguous decode shall be performed. If range is greater than 160 NM, the detection attempt shall be discontinued and the track information discarded. Detection shall be attempted if squitters continue to be received. If the globally decoded range remains greater than 160 NM, the track information shall continue to be discarded. Note.— If the aircraft is approaching, detection will succeed when the range decreases to less than or equal to 160 NM. 2.6.8.2.2.1.2 Track monitoring. After detection, range shall be monitored during each surveillance update. If range is greater than 170 NM, the track shall be dropped. Note.— The use of 160 NM for detection and 170 NM for track drop provides hysteresis that avoids reacquiring a track that was just dropped due to long range. Thus a track dropped at 170 NM would not be reacquired unless its range dropped to less than or equal to 160 NM. 2.6.8.2.2.2 Decoding of surface position. Using the range monitoring technique for decoding squitters in the surface format, the same process as above shall be used except that the track shall be initiated at 40 NM and dropped at 42.5 NM. 2.6.8.2.3 Emitter centered local decoding In this approach, the most recent position of the emitter shall be used as the basis for the local decoding. Note.— This produces an unambiguous decoding at each update, since the transmitting aircraft cannot move more than 360 NM between position updates. 2.6.8.2.4 Technique application The range monitoring technique shall only be used for ranges less than or equal to 180 NM, for example in air-to-air applications. For ground stations (i.e. non-aircraft implementations) that are required to operate at ranges in excess of 180 NM, only the emitter centred technique can shall be used. Note.— The emitter centered technique can be used for both airborne receivers and ground stations. 2007/70/II. szám Part I Annex 10 — Aeronautical Telecommunications 5-95 28/11/02 No. 77 TABLES FOR SECTION 2 Tables are numbered 2-X where “X” is the decimal equivalent of the BDS code Y,Z where Y is the BDS1 code and Z is the BDS2 code, used to access the data format for a particular register. The following tables are not included: 2-1 2-2 to 2-4 (Used by the linked Comm-B protocol) 2-13 to 2-14 (Reserved for air/air state information) 2-15 (Reserved for ACAS) 2-17 to 2-22 2-35 (Reserved for antenna position) 2-36 (Reserved for aircraft parameters) 2-38 to 2-47 2-49 to 2-63 2-70 to 2-71 2-73 to 2-79 2-87 to 2-94 2-102 to 2-111 (Reserved for extended squitter) 2-112 to 2-224 2-225 to 2-226 (Reserved for Mode S byte) 2-227 to 2-240 2-243 to 2-255 2007/70/II. szám Annex 10 — Aeronautical Telecommunications Volume III 5-96 28/11/02 No. 77 Table 2-5. BDS code 0,5 — Extended squitter airborne position MB FIELD PURPOSE: To provide accurate airborne position information. Surveillance status shall be coded as follows: = No condition information = Permanent alert (emergency condition) 2 = Temporary alert (change in Mode A identity code other than emergency condition) = SPI condition Codes 1 and 2 shall take precedence over code 3. When horizontal position information is unavailable, but altitude information is available, the airborne position message shall be transmitted with a format type code of zero in bits 1-5 and the barometric pressure altitude in bits 9 to 20. If neither horizontal position nor barometric altitude information is available, then all 56 bits of BDS 0,5 shall be zeroed. The zero format type code field shall indicate that latitude and longitude information is unavailable, while the zero altitude field shall indicate that altitude information is unavailable. FORMAT TYPE CODE (specified in 2.3.1) SURVEILLANCE STATUS (specified in 2.3.2.6) SINGLE ANTENNA FLAG (SAF) (specified in 2.3.2.5) ALTITUDE (specified by the format type code) This is (1) the altitude code (AC) as specified in 3.1.2.6.5.4 of Annex 10, Volume IV but with the M-bit removed or (2) the GNSS height (HAE) TIME (T) (specified in 2.3.2.2) CPR FORMAT (F) (specified in 2.3.2.1) MSB ENCODED LATITUDE (CPR airborne format specified in 2.6.1 to 2.6.5) LSB MSB ENCODED LONGITUDE (CPR airborne format specified in 2.6.1 to 2.6.5) LSB 2007/70/II. szám Part I Annex 10 — Aeronautical Telecommunications 5-97 28/11/02 No. 77 Table 2-6. BDS code 0,6 — Extended squitter surface position MB FIELD PURPOSE: To provide accurate surface position information. FORMAT TYPE CODE (specified in 2.2.3.1) MOVEMENT (specified in 2.3.3.1) STATUS for ground track: 0 = Invalid, 1 = Valid MSB = 180 (specified in 2.3.3.2) GROUND TRACK (TRUE) LSB = 360/128 TIME (T) (specified in 2.3.2.2) CPR FORMAT (F) (specified in 2.3.2.1) MSB ENCODED LATITUDE 17 bits (specified in 2.6.1 to 2.6.4 and 2.6.6) LSB MSB ENCODED LONGITUDE 17 bits (specified in 2.6.1 to 2.6.4 and 2.6.6) LSB 2007/70/II. szám Annex 10 — Aeronautical Telecommunications Volume III 5-98 28/11/02 No. 77 Table 2-7. BDS code 0,7 — Extended squitter status MB FIELD PURPOSE: To provide information on the capability and status of the extended squitter rate of the transponder. Transmission rate subfield (TRS) shall be coded as follows: = No capability to determine surface squitter rate = High surface squitter rate selected = Low surface squitter rate selected = Reserved Altitude type subfield (ATS) shall be coded as follows: = Barometric altitude = GNSS height (HAE) Aircraft determination of surface squitter rate: For aircraft that have the capability to automatically determine their surface squitter rate, the method used to switch between the high and low transmission rates shall be as follows:

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