definition of spacing based on spacing reference point, srp

Definition of Spacing based Definition of Spacing based ononSpacing Reference Point, Spacing Reference Point, SRPSRPPresentation of a proposal for a generic definition of spacing to be used for ASAS spacing applications.

Most of the work on a spacing definition has been performed by SAS within the frame of NUP I and NUP II.

Presented at the ASAS Thematic Network Workshop 07OCT 2003 by:Capt. Michael Agelii, representing Aviator System

Spacing Definition based on SRP 2

Need for a definition of Need for a definition of spacingspacing• Spacing is a defined distance between two aircraft

denoted as Leader and Follower• In order to measure a distance between the leader and

follower in space you must define along which line or curves in space the distance shall be measured.

• The great circle track between two aircraft is a truly useful representation of spacing only in the special case when both aircraft are flying with the same track and in line.

• In order to be able to use spacing operationally where aircraft frequently alter their track, we must broaden the definiton to encompass curves in space and track changes.

• It is an advantage to convert the defined distance to time by using follower ground speed.


Basic requirements on a Basic requirements on a definition of spacingdefinition of spacing• Common to all stakeholders

All stakeholders must have the same definition of the spacing dist/time.

• Operational functionalityFor maximum benefit spacing should be possible in as many flight situations as possible.

• Generic PropertiesThe same generic definition should encompass:

– ”All” ASAS spacing applications (C&P excluded)– Both distance and time definitions– ADS-B and TIS-B technical solutions


Spacing onlySpacing only

The SRP spacing definition does

not provide separation!!!


Spacing onlySpacing only

The SRP spacing definition is a tool to enhance traffic

flow!!!


Basic IdeaBasic Idea

• Spacing Reference Point SRPUsed to derive the spacing distance Ss

SRP

LF

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls



• Spacing Reference Point SRP (fixed)Used to derive the spacing distance Ss

SRPf

LF

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls



• Spacing Reference Point SRP (dynamic)Used to derive the spacing distance Ss

SRPd

LF

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls



• Spacing Reference Point SRP (fixed)Used to derive the spacing distance Ss

SRPf

LF

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

Let´s start with fixed SRP



• Spacing Reference Point SRP (fixed) Used to derive the spacing distance Ss

SRPf

LF

Ls = (L – W1 - SRP)

Fs = (F – W1 - SRP)

Ss = Fs - Ls

W1




SRPf L

F

Ls = (L – W3 – W4 - SRP)

Fs = (F – W1 - W2 – W3 – W4 - SRP)

Ss = Fs - Ls

W2W4

W3

W1




SRPf

L

F

Ls = (L – W2 – W3 – W4 - SRP)

Fs = (F – Y3 – W3 – W4 - SRP)

Ss = Fs - Ls

W2W4

W3

W1

Y3


Link sequence

Sequence determined by AMAN/Controller

Spacing executed by indiviual aircraft/pilots

Separation monitored by Controller

SRP



• Spacing Reference Point SRP (dynamic)Used to derive the spacing distance Ss

SRPd

LF

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

Let´s go on to dynamic SRP



• Spacing Reference Point SRP (dynamic)Used to derive the spacing distance Ss L

F

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls




F

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls




F

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

L-track = 260 dgr

F-track = 260 dgr

Delta-track = 0 dgr




F

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

L-track = 260 dgr

F-track = 260 dgr

Delta-track = 0 dgr

Standard rate turn = 3 dgr/sec = 180 dgr/60 sec



• Spacing Reference Point SRP (dynamic)Used to derive the spacing distance Ss L F

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

L-track = 260 dgr

F-track = 275 dgr

Delta-track = 15 dgr


SRP = 5 sec ahead of target(based on Leader ground speed)

5 s




F

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

L-track = 260 dgr

F-track = 290 dgr



SRP = 10 sec ahead of target

10 s




FLs = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

L-track = 260 dgr

F-track = 320 dgr




20 s




FLs = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

L-track = 260 dgr

F-track = 350 dgr




30 s




F

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

L-track = 260 dgr

F-track = 035 dgr




45 s




FLs = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

L-track = 260 dgr

F-track = 080 dgr




60 s




F

Ls = (L – SRP)

Fs = (F – SRP)

Ss = Fs - Ls

L-track = 260 dgr

F-track = 080 dgr




60 s


2T algorithm 2T algorithm

• Two Turn distance algorithmUsed to derive the spacing distance Ss closer to real flight path L

F

Ls = (L – SRP)

Fs = (F – 2T algorithm - SRP)

Ss = Fs - Ls

60 s

Let´s introduce curves



• The ”Two Turn” distance algorithm has been developed in a thesis by mathematics student Robert Lundmark on assignment by SAS within the framework of NUP II.

• The complete thesis can be downloaded from the NUP webside at:www.nup.nu Documents/General Documents/sep-algo

http://www.nup.nu/



• The shortest possible way to fly from follower position to leader position and end up in the same direction is at most via two turns and a straight line.



• The shortest possible way to fly from follower position to leader position and end up in the same direction is at most via two turns and a straight line.

Leader position can of course be substituted by SRPd


2T distance 2T distance algorithm using algorithm using SRPSRPdd

Ls = (L – SRP)


Spacing = Fs - Ls +

6 0 s

L

F+



Ls = (L – SRP)


Spacing = Fs - Ls +

6 0 s

L

F+


Ls = (L – SRP)


Spacing = Fs - Ls +

2T distance 2T distance algorithm using algorithm using SRPSRPdd 57 s

F+

L


Ls = (L – SRP)


Spacing = Fs - Ls +

2T distance 2T distance algorithm using algorithm using SRPSRPdd 5 4 s

F+

L


Ls = (L – SRP)


Spacing = Fs - Ls +


F+

L


Ls = (L – SRP)


Spacing = Fs - Ls +


F

+

L


Ls = (L – SRP)


Spacing = Fs - Ls +


17 s

F

+

L


Ls = (L – SRP)


Spacing = Fs - Ls +


14 s

F

+

L


Ls = (L – SRP)


Spacing = Fs - Ls +


11 s

F

+

L


Ls = (L – SRP)


Spacing = Fs - Ls +


8 s

F

+

L


Ls = (L – SRP)


Spacing = Fs - Ls +


6 s

F

+

L


Ls = (L – SRP)


Spacing = Fs - Ls +


3 s F

+

L


Ls = (L – SRP)


Spacing = Fs - Ls +


0 s F

+

L


Ls = (L – SRP)


Spacing = Fs - Ls +



Operational applicability of Operational applicability of SRPSRPdd

•MergingIn managed or unmanaged airspace in order to establish the desired spacing in the required sequence.

•Spacing•Spacing to TIS-B aircraft

•Spacing to aircraft not flying a predefined route


Input data to the definition Input data to the definition of Ssof Ss• Leader input data (ADS-B/TIS-B)

– Position– Track– Velocity (GS)– Distance to SRP Ls (fixed SRP only)– SRPf (fixed SRP only)

• Follower input data (onboard + ADS-B for ground)– Position– Track– Velocity (GS)– Distance to SRP Fs– SRPf (fixed SRP only)


Addition to basic ADS-B Addition to basic ADS-B datadata(for fixed SRP only)(for fixed SRP only)

• Distance to SRP (Ls)– Broadcast as extension to data– Distance to SRP as 10 bit info (99.9)

• SRP– Broadcast as extension to data– SRP as lat, long or Nav database reference


Operational applicability Operational applicability with SRPwith SRP• In-Trail

• STAR (incl. diff STAR) ADS-B• Straight and curved ADS-B TIS-B

• Merging• Merging STARs ADS-B• Free space merging ADS-B TIS-B


The Spacing Algorithm The Spacing Algorithm (highlevel)(highlevel) Define SRP method

1. Select SRP method to be used Define distances to SRPf

3. Retrieve Follower distance to SRP from FMS4. Retrieve Leader distance to SRP from ADS-B data

or Define distances to SRPd

2. Calculate Leader distance to SRP3. Calculate Follower distance to SRP

Derive spacing distance and time4. Compare Leader dist to SRP with Follower distance to

SRP5. Convert spacing distance to spacing time by dividing

with follower GS


Thank YouThank You

• Remember!• This is not a final definition of

spacing• …but

• – It may be a starter!!!

definition of spacing based on spacing reference point, srp

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