Algorithms Overview

Algorithms & Processing Overview

Looking for the full computational reference? See docs/COMPUTATIONAL_REFERENCE.md for comprehensive algorithm documentation including the ADL ingest cycle, ETA engine, route parsing, boundary detection, GDP/GS slot assignment, TMI compliance, trajectory tiering, weather integration, and performance tuning.

This documentation describes the core algorithms and data processing systems that power PERTI. The system processes VATSIM flight data every 15 seconds through a sophisticated pipeline that calculates ETAs, tracks flight phases, parses routes, and logs trajectory history.

---

System Architecture

VATSIM API (every 15 seconds)
         │
         ▼
┌──────────────────────────────────────────────────────────────────────┐
│           sp_Adl_RefreshFromVatsim_Staged (V9.3.0)                   │
│  • Delta detection → Normalize tables → Defer ETAs → Log trajectories│
└──────────────────────────────────────────────────────────────────────┘
         │
         ├──────────────┬──────────────┬──────────────┬────────────────┐
         ▼              ▼              ▼              ▼                ▼
   ┌──────────┐  ┌──────────┐  ┌──────────┐  ┌──────────┐     ┌──────────┐
   │   ETA    │  │Trajectory│  │   OOOI   │  │  Route   │     │ Boundary │
   │  Engine  │  │  Logger  │  │ Detector │  │  Parser  │     │ Detector │
   └──────────┘  └──────────┘  └──────────┘  └──────────┘     └──────────┘

---

Core Algorithm Documentation

Algorithm	Purpose	Primary Users
Algorithm-ETA-Calculation	Estimates arrival times using aircraft performance, route geometry, and TMI delays	Traffic Managers, GDP Planning
Algorithm-Trajectory-Tiering	Determines logging frequency based on flight phase and relevance	System Performance, Historical Analysis
Algorithm-Zone-Detection	Detects OOOI phases using airport geometry and speed-based fallbacks	OOOI Tracking, Ground Operations
Algorithm-Route-Parsing	Parses flight plan routes into waypoints with GIS coordinates	Route Plotting, Demand Analysis
Algorithm-Data-Refresh	Main pipeline processing VATSIM data every 15 seconds	System Operations, Integration

---

Performance Targets

Metric	Target	Description
Refresh Cycle	< 15 seconds	Complete data refresh within VATSIM API window (SP + deferred ETA)
ETA Accuracy	± 5 minutes	For flights > 100nm from destination
Zone Detection	< 0.5 seconds	Batch processing all relevant flights
Route Parsing	< 200ms/route	Including airway expansion and GIS resolution

---

Data Flow Summary

Input Sources

• VATSIM API - Real-time pilot positions, flight plans, prefiles
• FAA NASR - Navigation fixes, airways, airports, procedures
• OSM Overpass - Airport geometry for zone detection

Output Consumers

• TSD/Route Plotter - Flight positions and routes
• GDT/TMI Tools - ETAs for GDP/GS planning
• NOD Dashboard - Operational status
• Demand Visualization - Traffic forecasting

---

GDP Algorithm Redesign (CASA-FPFS + RBD Hybrid)

The Ground Delay Program algorithm was redesigned across four phases to implement a CASA-FPFS + RBD hybrid approach.

Algorithm Overview

Component	Description
CASA	Compression After Slot Assignment -- assigns slots first, then compresses to minimize total delay
FPFS	First Planned First Served -- allocates slots in order of original estimated arrival time
RBD	Ration By Distance -- distributes delay proportionally based on flight distance from destination

Implementation Phases

Phase	Migration	Key Deliverables
Phase 1	Migration 037	Bug fixes, compress.php endpoint, batch optimization
Phase 2	Migration 038	FPFS+RBD algorithm, adaptive reserves, FlightListType TVP rebuild
Phase 3	Migration 039	sp_TMI_ReoptimizeProgram orchestrator, reoptimize.php endpoint
Phase 4	Migration 041	Reversal metrics, anti-gaming flags, GDT UI observability

Key Stored Procedures (GDP)

Procedure	Function
sp_TMI_AssignSlots	FPFS+RBD slot assignment with adaptive reserves
sp_TMI_CompressProgram	CASA compression to fill unused slots
sp_TMI_ReoptimizeProgram	Orchestrator combining compression + reassignment

TMI-to-ADL Sync

The executeDeferredTMISync() function in the ADL daemon synchronizes TMI control data back to the ADL flight tables on a 60-second cycle. Multi-program precedence rules apply: Ground Stops take priority, followed by the maximum CTD across active GDPs.

Note: The automatic daemon reoptimization cycle (2-5 minute intervals) is pending implementation post-hibernation.

---

Quick Reference

Key Stored Procedures

Procedure	Function
sp_Adl_RefreshFromVatsim_Staged	Main refresh orchestrator (V9.3.0, delta detection + deferred ETA)
sp_CalculateETABatch	Consolidated ETA calculation
sp_ProcessTrajectoryBatch	Trajectory logging with tier evaluation
sp_ProcessZoneDetectionBatch	OOOI zone detection
sp_ParseRoute	Route parsing and GIS resolution
sp_TMI_AssignSlots	GDP FPFS+RBD slot assignment
sp_TMI_CompressProgram	GDP CASA compression
sp_TMI_ReoptimizeProgram	GDP reoptimization orchestrator

Key Functions

Function	Returns
fn_GetTrajectoryTier	Tier 0-7 based on flight state
fn_IsFlightRelevant	1 if flight is in covered airspace
fn_DetectCurrentZone	Zone type (PARKING/TAXIWAY/RUNWAY/etc)
fn_GetAircraftPerformance	Climb/cruise/descent speeds for aircraft

---

Related Documentation

• Acronyms - Timing acronym reference (ETA, OOOI, etc.)
• Database-Schema - Table structure reference
• API-Reference - API endpoints consuming this data
• Troubleshooting - Common issues and solutions