| Significance | Code | Meaning |
|---|
| FIR | EGTT | London FIR | | | / | | | Qualifiers | Q | | | | OB | Obstacle | | | CE | erected | | | / | | | Traffic | I | IFR traffic affected | | | V | VFR traffic affected | | | / | | | Purpose | M | Miscellaneous | | | / | | | Scope | A | Aerodrome information | | | E | En-Route information | | | / | | | From flight level | 000 | Surface | | | / | | | Up to flight level | 001 | 100 feet QNE | | | / | | | Centre Latitude | 5139N | 51° 39' North' | | Centre Longitude | 00020W | 0° 20' West | | Radius of area affected | 001 | 1 nautical miles |
| | UNLIT GROUND OBSTACLE POST ( IN SITU DUE WORK IN PROGRESS ) WITHIN 10M RADIUS POSITION 513924.1N 0001931.1W ( NORTH SIDE GRASS OPPOSITE HELIPAD,ELSTREE AERODROME ). HEIGHT 2FT ABOVE GROUND LEVEL,332FT ABOVE MEAN SEA LEVEL |
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