Algorithm Zone Detection

Zone Detection Algorithm (OOOI)

The zone detection system automatically identifies flight OOOI (Out-Off-On-In) phases by detecting when aircraft transition between airport zones. The system uses OpenStreetMap airport geometry data with speed-based fallback detection.

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For Traffic Managers

What OOOI Tracking Shows

OOOI times represent key operational milestones:

Event	Definition	Trigger
OUT	Gate departure	Aircraft leaves PARKING zone
OFF	Wheels up	Aircraft enters AIRBORNE from RUNWAY
ON	Wheels down	Aircraft enters RUNWAY from AIRBORNE
IN	Gate arrival	Aircraft enters PARKING zone

Zone Types

The system tracks aircraft through these airport zones:

┌─────────────────────────────────────────────────────────────┐
│                     AIRPORT ZONES                           │
├─────────────────────────────────────────────────────────────┤
│                                                             │
│   ┌─────────┐    ┌─────────┐    ┌─────────┐    ┌─────────┐ │
│   │ PARKING │───►│ TAXILANE│───►│ TAXIWAY │───►│  HOLD   │ │
│   │ (Gate)  │    │ (Apron) │    │ (Alpha) │    │ (Short) │ │
│   └─────────┘    └─────────┘    └─────────┘    └────┬────┘ │
│                                                      │      │
│                                                      ▼      │
│                                               ┌─────────┐   │
│                                               │ RUNWAY  │   │
│                                               │ (28L)   │   │
│                                               └────┬────┘   │
│                                                    │        │
│                                                    ▼        │
│                                               ┌─────────┐   │
│                                               │AIRBORNE │   │
│                                               └─────────┘   │
└─────────────────────────────────────────────────────────────┘

Operational Metrics Derived from OOOI

Metric	Calculation	Use
Taxi-Out Time	OFF - OUT	Departure efficiency
Block Time	IN - OUT	Total gate-to-gate
Air Time	ON - OFF	Actual flight time
Taxi-In Time	IN - ON	Arrival efficiency
Hold Time	RUNWAY_ENTERED - HOLD_ENTERED	Departure queue delays

Coverage

Zone detection is enabled for 201 airports with OSM geometry data:

• All Core30/OEP35 airports
• Major regional airports
• Busy GA fields

Airports without geometry data use speed-based fallback detection.

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For Technical Operations

Monitoring Zone Detection

-- Recent zone transitions
SELECT TOP 20
    ze.event_utc,
    c.callsign,
    ze.airport_icao,
    ze.from_zone,
    ze.to_zone,
    ze.detection_method,
    ze.confidence
FROM dbo.adl_zone_events ze
JOIN dbo.adl_flight_core c ON c.flight_uid = ze.flight_uid
ORDER BY ze.event_utc DESC;

Expected Detection Methods:

Method	Description	Confidence
OSM_GEOMETRY	Matched against OSM polygons	0.75-0.99
SPEED_FALLBACK	Speed-based heuristic	0.50-0.60

Health Checks

-- Zone detection coverage
SELECT 
    COUNT(DISTINCT airport_icao) AS airports_with_geometry
FROM dbo.airport_geometry
WHERE is_active = 1;

-- Detection method distribution (last hour)
SELECT 
    detection_method,
    COUNT(*) AS transitions
FROM dbo.adl_zone_events
WHERE event_utc > DATEADD(HOUR, -1, GETUTCDATE())
GROUP BY detection_method;

-- Current zone distribution
SELECT 
    current_zone,
    COUNT(*) AS flights
FROM dbo.adl_flight_core
WHERE is_active = 1
  AND current_zone IS NOT NULL
GROUP BY current_zone;

Common Issues

Symptom	Cause	Resolution
No zone events	Procedure not running	Check refresh daemon
All SPEED_FALLBACK	Missing airport geometry	Run OSM import
Missing OUT events	Aircraft spawned on taxiway	Normal for VATSIM
False RUNWAY detections	Speed too high on taxiway	Check speed thresholds
Duplicate IN events	Repositioning at gate	Normal behavior

Performance

Target: < 500ms for batch processing

-- Check zone detection step timing
SELECT 
    step9_zone_ms,
    zone_transitions
FROM (
    SELECT TOP 10 * FROM dbo.adl_run_log ORDER BY run_utc DESC
) recent;

V3.0 Optimizations:

• Removed STBuffer() - uses direct STDistance()
• Bounding box pre-filter eliminates flights >12nm from airport
• Skips stationary flights checked within 30 seconds

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For Developers

Algorithm Overview

1. Identify flights needing zone check
   - Pre-departure (hasn't taken off yet)
   - Arriving (>80% complete)
   
2. Apply bounding box pre-filter
   - Skip flights >0.2° lat or >0.25° lon from airport
   
3. Skip stationary flights
   - If groundspeed < 5 and checked within 30 seconds
   
4. Calculate zone using STDistance
   - Match against airport_geometry polygons
   - Or use speed-based fallback
   
5. Log zone transitions
   - Only when zone changes from previous
   
6. Update OOOI times
   - Based on specific zone transitions

Zone Detection Function

-- fn_DetectCurrentZone logic
1. If AGL > 500ft → AIRBORNE
2. Check OSM geometry match (within 100m)
3. Priority order: PARKING > GATE > HOLD > RUNWAY > TAXILANE > TAXIWAY > APRON
4. If no match, speed-based fallback:
   - < 5 kts → PARKING
   - 5-35 kts → TAXIWAY
   - > 35 kts on ground → RUNWAY

OOOI Time Triggers

Departure Events:

Event	From Zone	To Zone	Column Updated
OUT	PARKING	Any other	out_utc
Taxiway entry	PARKING/APRON	TAXIWAY	taxiway_entered_utc
Hold entry	TAXIWAY	HOLD	hold_entered_utc
Runway entry	TAXIWAY/HOLD	RUNWAY	runway_entered_utc
OFF	RUNWAY	AIRBORNE	off_utc, atd_utc

V2.1 Note: atd_utc (Actual Time of Departure) is now set on takeoff for ETA accuracy analysis.

Arrival Events:

Event	From Zone	To Zone	Column Updated
ON	AIRBORNE	RUNWAY	on_utc, ata_runway_utc
Runway exit	RUNWAY	TAXIWAY	taxiway_arr_utc
IN	TAXIWAY/APRON	PARKING	in_utc

V2.1 Note: ata_runway_utc (Actual Time of Arrival at Runway) is now set on touchdown for ETA accuracy analysis.

Database Tables

airport_geometry - OSM polygon data:

Column	Type	Description
geometry_id	INT	Primary key
airport_icao	CHAR(4)	Airport code
zone_type	VARCHAR(16)	PARKING/TAXIWAY/RUNWAY/etc
zone_name	VARCHAR(64)	e.g., "Taxiway A", "Gate B22"
geometry	GEOGRAPHY	Polygon shape
is_active	BIT	Enable/disable flag

adl_zone_events - Transition log:

Column	Type	Description
event_id	BIGINT	Primary key
flight_uid	BIGINT	Flight reference
event_utc	DATETIME2(0)	When transition occurred
event_type	VARCHAR(16)	TRANSITION
airport_icao	CHAR(4)	Which airport
from_zone	VARCHAR(16)	Previous zone
to_zone	VARCHAR(16)	New zone
zone_name	VARCHAR(64)	Specific zone name
lat/lon	DECIMAL	Position at transition
detection_method	VARCHAR(32)	OSM_GEOMETRY or SPEED_FALLBACK
confidence	DECIMAL(3,2)	0.00-1.00

Spatial Query Optimization

-- V3.0 optimized approach (no STBuffer)
SELECT TOP 1 zone_type
FROM dbo.airport_geometry ag
WHERE ag.airport_icao = @airport
  AND ag.geometry.STDistance(geography::Point(@lat, @lon, 4326)) < 100
ORDER BY 
    CASE zone_type
        WHEN 'PARKING' THEN 1
        WHEN 'RUNWAY' THEN 4
        WHEN 'TAXIWAY' THEN 6
        ELSE 99
    END,
    ag.geometry.STDistance(geography::Point(@lat, @lon, 4326));

Performance comparison:

Approach	Execution Time
STBuffer + STIntersects (V1)	~1.8 seconds
Direct STDistance (V2.0)	~0.3-0.5 seconds

Version History

Version	Date	Changes
V1.0	2025-12	Initial OSM geometry matching
V2.0	2026-01	Performance optimization (STDistance vs STBuffer)
V2.1	2026-01-13	Added atd_utc and ata_runway_utc for ETA accuracy analysis

Speed-Based Fallback Logic

When OSM geometry is unavailable:

CASE
    WHEN @groundspeed_kts < 5 THEN 'PARKING'
    WHEN @groundspeed_kts BETWEEN 5 AND 35 THEN 'TAXIWAY'
    WHEN @groundspeed_kts > 35 AND @agl < 100 THEN 'RUNWAY'
    WHEN @agl BETWEEN 100 AND 500 THEN 'AIRBORNE'
    ELSE 'UNKNOWN'
END

OSM Import Process

Airport geometry is imported from OpenStreetMap via Overpass API:

# PowerShell import script queries:
# - aeroway=taxiway
# - aeroway=runway
# - aeroway=parking_position
# - aeroway=apron
# - aeroway=holding_position

Coverage: 201 airports prioritized by traffic volume.

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Related Documentation

• Acronyms#flight-status--delay - OOOI definitions
• Algorithm-Trajectory-Tiering - Uses zone for Tier 3 decisions
• Database-Schema - Table definitions
• Troubleshooting - OOOI tracking issues