(e) each of these tolerances is combined(e) each of these tolerances is combined by the root sum square (RSS) method; and

Section 10.8: Separation Standards—Lateral

10.8.1 Lateral Separation Buffer

10.8.1.1 The Lateral Separation buffer is 1 NM between the possible positions of two aircraft. (ICAO PANS-ATM, Chapter 5.)

10.8.2 Application of Lateral Separation

10.8.2.1 Lateral separation may be achieved by:

(a) establishing an aircraft’s position outside the BLSP; or

(b) applying an appropriate ATS surveillance system minimum; or

(c) applying a 1 NM buffer to the track or position of an aircraft which is determined relative to a prominent topographical feature, if:

(i) the aircraft is tracking visually; and

(ii) the aircraft is not more than 10 000 ft above the topographical feature; and

(iii) it is daytime.

10.8.2.2 Entry and Exit Points must be established by:

(a) application to a BLSP of slant range and DME equipment error corrections;

(b) application of RNAV tolerances;

(c) passage over a visual fix located on the opposite side of a BLSP from the area of conflict;

(d) passage over a positive radio fix located on the opposite side of a BLSP from the area of conflict;

(e) expiration of a time calculated using an estimate for a BLSP plus or minus:

(i) 5 minutes, if the estimate for the BLSP is within 30 min of an ATD, passage over a visual fix, positive radio fix, way point or ATS surveillance system position; or

(ii) half of the longitudinal time separation minimum applicable to the aircraft.

10.8.2.3 Aircraft transiting into an airspace in which larger tolerances are applied than that being exited are taken to be separated if:

(a) the smaller separation standard exists; and

(b) the aircraft are established on flight paths that will diverge by at least 15° until the larger separation standard is established; and

(c) the aircraft are RNAV approved to AUSEP, MNPS, GPSOCEANIC, RNP10 or RNP4.

10.8.2.4 A DME-based lateral separation entry/exit point must be calculated by:

(a) determining the ground distance from the DME site to the BLSP; then

(b) if the area of conflict (or part of it) is between the BLSP and the DME site, adding the slant range correction from Table 10.8-1 to the ground distance; then

(c) applying the correction for DME equipment error from Table 10.8-2 ensuring it is applied to a position outside the area of conflict.

10.8.2.5 Where the navigation tolerance is determined with reference to ground-based navigation aids, GPS distance may be used in lieu of a co-sited DME in the steps above.