Introduction

1. Introduction • This powerpoint describes possible limitations in the algorithms proposed to resolve duplicated waypoints, and proposes a possible solution • The next slide contains the current proposal for resolving duplicates

2. Current proposal DDuplicate identifier in [routeInformation] If a duplicate waypoint identifier is contained in the [routeinformations], as a [publishedidentifier] or as the place of a [placebearingdistance], then the appropriate version of that fix shall be selected from the Navigation Data Base on the basis of the following priority: Step 1. As the one matching the reference latitude/longitude, if any was uplinked Note: When duplication applies to the place of a [placebearingdistance], then following steps are not performed. Step 2. If it's the first en-route fix, as the first matching fix in the departure procedure/transition, if any Step 3. If it follows an airway, as the first matching fix on that airway Step 4. If it is followed by an airway, as the first matching fix on that airway Step 5. If it's the last en-route fix, as the first matching fix in the arrival or approach procedure/transition, if any Note: this can lead to situations where the duplication cannot be unambiguously resolved by the aircraft.

3. Enroute segment STU VWX YZA BCD ABC DEF GHI JKL MNO PQR • Example: Acft is uplinked “AT [DEF] CLEARED [STU VWX YZA BCD…]” • The new route should become [PPOS ABC DEF STU VWX YZA BCD…] • STU is a duplicated waypoint, however: • there is no reference lat/long for STU included in the clearance, and • there are also no airways in the clearance. • According to the proposed rules, the duplicated waypoint cannot be resolved (without flight crew intervention?)

4. Enroute segment STU VWX YZA BCD ABC DEF GHI JKL MNO PQR The proposal is to add a new rule: Step6: “The occurrence of the waypoint in the nav data base that is closest in distance to the previous waypoint in the newly constructed route” In this example, the proposal would result in the occurrence of waypoint STU that was closest in distance to DEF to be loaded See also the following example:

5. Enroute segment STU VWX YZA BCD ABC DEF GHI JKL MNO PQR • STU and VWX are both duplicated waypoints. STU includes a reference latitude/longitude; however: • there is no reference lat/long for VWX included in the clearance, and • there are also no airways in the clearance. • Duplicated waypoint STU is resolved using Step 1 (reference lat/long) • Once STU has been resolved, the proposed Step 6 allows the waypoint VWX closest in distance to STU to be loaded

6. Enroute segment STU VWX YZA BCD ABC DEF GHI JKL MNO PQR The addition of the proposed Step 6 would allow the resolving of: 1. Any duplicated waypoint contained in Ums 83R and 339; 2. The majority of duplicated waypoints in Ums 79R and 80R - A problem could still occur, however, if the duplicated waypoint was the first waypoint in the route information contained in Ums 79R or 80R

7. Enroute segment STU VWX YZA BCD ABC DEF GHI JKL MNO PQR • Example: Acft is uplinked “CLEARED [STU VWX YZA BCD…]” • The new route should become [PPOS STU VWX YZA BCD…] • STU is a duplicated waypoint, however: • there is no reference lat/long for STU included in the clearance, and • there are also no airways in the clearance. • According to the proposed rules (including the newly proposed Step 6), the duplicated waypoint cannot be resolved (without flight crew intervention?)

8. Enroute segment STU VWX YZA BCD ABC DEF GHI JKL MNO PQR To correct this limitation, the proposal is to add an additional new rule: Step7: “The occurrence of the waypoint in the nav data base that is closest in distance to the present position of the aircraft” In this example, the proposal would allow the occurrence of waypoint STU closest in distance to the present position of the aircraft to be loaded See also the following example:

9. Enroute segment STU VWX YZA BCD ABC DEF GHI JKL MNO PQR • STU and VWX are duplicated waypoints: • there are no reference lat/long for STU or VWX included in the clearance, and • there are also no airways in the clearance. • Duplicated waypoint STU is resolved using proposed Step 7 (closest waypoint to present position of the aircraft) • Once STU has been resolved, the proposed Step 6 allows waypoint VWX to be resolved

10. Proposal Add new Step 6: “The occurrence of the waypoint in the nav data base that is closest in distance to the previous waypoint in the newly constructed route” Add new Step 7: “The occurrence of the waypoint in the nav data base that is closest in distance to the present position of the aircraft” In addition, the Note after Step 1 would need to be amended to: Note: When duplication applies to the place of a [placebearingdistance], then steps 2 to 5 are not performed.