Implementation of the trajectory
Using the combination of the aircraft profiles and the city-pair flight route allocation, a 4-D trajectory can then be generated. Knowing the latitude/longitude of two waypoints, the distance can be calculated based on the Great Circle function. The reporting of this distance on the aircraft profile allows determining the flight level and speed at each waypoint along the trajectory. From the speed, the progressive distance and the departure time, an event-time can be allocated to each position.

This way, a full 4-D trajectory can be attributed to schedule data issued from Back Aviation database.
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Data sampling

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The objective of AERO2K is to assess emissions for the world, which requires collecting flight movement data for the world. Such a task requires an important preliminary work in terms of:
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Identifying contacts name within worldwide ATC authorities.

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Establishing contacts.

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Agreeing on the type of data to exchange.

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Receiving the data.

For this reason, the data collection was done in parallel with the development of the prototype tool. Flight data for Europe and North America (4-5-6 October 2000) could be obtained relatively quickly and used as a sample set of data for starting the prototype tool. The work could then start without data acquisition problems.

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The objective of WP2 in AERO2K was to construct a global aircraft movement database that represented as closely as possible the actual civil movements for 2002. In order to be representative of yearly global emission variations, it had to account for the seasonal, weekly and diurnal variation in air traffic. This objective was achieved by selecting periods of data collection for the world and by extending these data in creating aircraft movement inventory for days where no data were collected. This second function is described below in §3. The collection of data was divided into two tasks:
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Choosing the data collection period.

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Choosing the data to collect.

The choice of the data to collect was influenced by the availability of ATC data while the choice of the length of collection periods was influenced by the logistics of merging such data into a comprehensive annual data set. It was decided that the basis year for collecting the data would be 2002 in order to reduce the risk of not getting data not kept by ATC authorities. This risk did not concern North America and Europe but could have been true in Africa, Asia and South America.
2002 was also concerned by the application of RVSM (Reduced Vertical Separation Minimum) in Europe i.e. the decrease of the vertical separation between aircrafts in cruise from 2000 ft to 1000 ft. 2002 was thus considered as more representative of the new rules in aviation in Europe than 2001.

2.1. Data collection period
The choice of the data collection period was based on data available for the ECAC area and confirmed by data found for the US air traffic. An analysis of air traffic based on ECAC and US data showed that these two areas represented over 70% of the air traffic in the world (Figure 25). For both areas, the monthly traffic trends were examined in order to identify the key months and the suitable weeks.
Figure 25: Total scheduled aircraft departures estimated for the year 2000 by ICAO.

2.1.1. Selection of the key month in the ECAC area
　
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