ATFM (Air Traffic Flow Management) is conducted to respond demand for traffic increase and to keep safe and efficient flight at each sector. ATFM use “Traffic Capacity Index” that represents a controller workload to make a decision of ATFM control. In order to know this index, air traffic controller's task must be measured, analyzed and classified of each aircraft in each sector to obtain parameter of controller workload. The controller's task means the consideration of control instructions, the communication with pilot and surveillance. It is time consuming and laborious to obtain parameter of controller workload.

This paper notes traffic characteristic in each sector and presents a simple new method to calculate this “Traffic Capacity Index” instead of current method. The index obtained by current method has been compared with average number of controlled aircraft in each 15 sector at Tokyo Area Control Center. The result has shown that the index by current method is proportional to average number of controlled aircraft per 30 minutes and its proportion coefficient corresponds to the average parameter of controller workload.

Then this paper proposed a method by number of proximity aircraft and parameter “K” at each sector to calculate “Traffic Capacity Index”. The close relationship between the index by proposed method and the index by current method has been shown. If the number of arriving aircraft is fewer than the average of all sector, this parameter “K” can be expressed by a simple function in terms of average number of controlled aircraft.

This paper describes experiments and simulations to consider the reduction of multipath error, with the aim of realizing a precise passive positioning system using Mode S signal on airport surfaces. There are many reflective objects on airport surfaces, and broad pattern fixed antennas used for passive positioning systems, must be influenced by the multipath.

The simulation of the multipath error characteristic of various pulse time of arrival detection methods was performed in order to study the influence of the multipath. As the simulation results showed, influence of the multipath remains even if delay time is long by the half-amplitude point method, which is widely used for the detection of pulse time of arrival (TOA). The correlation method, which is used for GPS, the DAC (Delay Attenuate and Compare) method, and the least square matching method, which extends DAC, can reduce the error created by an obstacle exceeding the delay time of the multipath by about 40ns, so the obstacles that influence an airport surface could be limited. The peak multipath errors of the DAC method and the least square matching method are less than half that of the correlation method. Compared with the correlation method, the multipath mitigation effect of the DAC method and the least square matching method, which carry out time detection in the early portion of a pulse waveform with low possibility of delayed multipath overlapping, are clear. However, since delay time is small, the influence of ground reflection can not be avoided. Although the error of the least square matching method is the smallest of these methods, the DAC method is practical at present, taking into account data processing load.

An experimental system was developed using optical fiber signal transmission. Termed OCTPASS (Optically Connected PAssive Surveillance System), it enables precise synchronization between the receiving stations of an airport surface passive positioning system. An experiment conducted at Sendai Airport showed that the error using the DAC method is less than half that compared with the correlation method. The experimental results of positioning error using the DAC method, without using smoothing filter obtained on the runway and taxiway were less than the 7.5m (2RMS) required for airport surface surveillance. It is considered necessary that M/D (Multipath to Direct signal level ratio) be reduced to less than one, taking into account the height and position of the installed receiving antennas.