Obstacle surveys. eTOD

ETOD is an acronym for Electronic Terrain and Obstacle Database. eTOD databases were implemented by Amendment 33 to Annex 15 to the Convention on International Civil Aviation (ICAO Annex 15). All ICAO participating states were expected to adopt the new standard by 2012-2014.

ETOD data sets should be provided according to four basic coverage areas:

• Area 1 — the entire territory of a state.
• Area 2 — 45-km radius around the airport, or terminal control area (Area 2d), sub-divided in 4 smaller sections 2a, 2b, and 2c.
• Area 3 — aerodrome or heliport area extending from the runway centre line to 90 m and from other parts of aerodrome movement area to 50 m.
• Area 4 — the radio altimeter operating area runway, category II or III; the width of the Area 4 is 60 m on either side of the extended runway centre line while the length is 900 m from the runway threshold.

Theoretically airports must be situated in areas where the airspace is free from obstructions in the vicinity and takeoff - departure paths. But it is far from true in practice. Airports located in metropolitan areas are often surrounded with buildings, constructions, towers, cranes etc. Airports in mountainous regions are often configured in valleys between mountain ranges or on high plateaus. That is why the quality aeronautical information and terrain data are crucial.

Zesmill’s approach

Three measurements are required for obstacle data — the horizontal location, the height of obstacles above the ground, and the base elevation of the object (the ground level). The first obtained using orthorectified imagery and can be verified by ground geodetic measurements. The heights are obtained from LIDAR survey data or photogrammetric measurements, and must be verified by ground survey. The other important aim of the filed survey is to collect additional information about obstacles like type, fragility, lighting, removability etc.

Obstacle Limitation Surfaces (OLS) are imaginary surfaces which extend beyond the boundary of the airport, the penetration of which represent an obstacle to the air navigation. Obstacle OLS are modeled in GIS using 3D maps derived from DTM or DEM. The purpose is to identify all objects that infringe OLS and must be included into the obstacle dataset.

The arrangement of eTOD requires the collection of precise and comprehensive geospatial information with the help of aerial imaging and conventional ground survey methods. Zesmill is dedicated to providing large and small airports with eTOD data sets in accordance with all ICAO regulations. We offer a wide range of high quality surveying and mapping services at very reasonable prices. The typical eTOD project costs are 95,000-135,000 EUR for a single-runway airport, depending on topography and building density.