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Obstacle Data - Structure Types

The Obstacles Team labels all structures in the Digital Obstacle File (DOF) database using the obstacle type categories listed below. Please note that some of these categories differ from obstacle types used by FAA's regulatory specialists.

Bold text indicates the FAA's most frequently received and processed obstacle types.
  • AG EQUIP (agricultural equipment)
  • AMUSEMENT PARK STRUCTURE
  • ANTENNA
  • ARCH
  • BLDG-TWR (latticework greater than 20' on building)
  • BRIDGE
  • BUILDING
  • CABLE CAR
  • CATENARY (transmission line span/wire/cable) (* See Note below)
  • CONTROL TOWER (airport control tower)
  • COOLING TOWER (nuclear cooling tower)
  • CRANE (permanent)
  • DAM
  • DOME
  • ELECTRICAL SYSTEM (components of an electrical distribution system)
  • ELEVATOR
  • FENCE
  • GATE
  • GENERAL UTILITY (components of a general utility system)
  • GRAIN ELEVATOR
  • HANGAR
  • HEAT COOL SYSTEM (components of a heating and cooling distribution system)
  • LANDFILL
  • LGHTHOUSE
  • MET (meteorological tower)
  • MONUMENT
  • NATURAL GAS SYSTEM (components of a natural gas distribution system)
  • NAVAID (airport navigational aid)
  • PIPELINE PIPE
  • POLE (flag pole; light pole)
  • POWER PLANT (buildings and equipment used for creating electric/nuclear power)
  • REFINERY (buildings and equipment used for purifying crude materials)
  • RIG (off-shore platform)
  • SHIP
  • SIGN
  • SILO
  • SOLAR PANELS
  • SPIRE (steeple)
  • STACK (chimney; industrial smokestack)
  • STADIUM
  • TANK (water; fuel)
  • TETHERED BALLOON (weather; other reconnaissance)
  • TETRAHEDRON (solid, pyramid-shaped landing direction indicator)
  • TOWER
  • TRAMWAY
  • TRAMWAY PYLON
  • T-L TOWER (* See Note below)
  • UTILITY POLE (telephone pole, or pole of similar height, supporting wires)
  • WALL
  • WIND INDICATOR
  • WINDMILL (wind turbine)
  • WINDSOCK (flexible, mast-mounted cylinder showing wind direction and strength)

*Note: For aeronautical charting purposes, the Obstacles Team differentiates between the supporting structures (called Transmission Line Towers) that hold up the power wires, and the actual wires (called Catenaries) that are strung between the towers. Although these two types of items function together, they are still physically different pieces of equipment.

When submitting power line project data to your regional office, please remember to clearly state the physical structure type for each individual case study - a tower/pole or a catenary/wire/span/conductor - in the "Description of Proposal" field. Thank you.

If you have any questions about this subject, please see Aeronautical Inquiries.

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This page was originally published at: https://www.faa.gov/air_traffic/flight_info/aeronav/obst_data/structuretypes/