Observation of the cruising height of an aircraft by NAMS (Navigation Accuracy Measurement System) is so far the only trial to obtain data on height keeping errors from the ground. NAMS has been installed under a trunk airway and collecting the data automatically. Information about assigned flight levels of aircraft is necessary for studying height keeping errors of aircraft.

Therefore, data on heights of aircraft obtained by NAMS must be correlated with flight progress strips in order to confirm assigned flight levels for normally operated aircraft. The meteorological data processing function was added on NAMS to facilitate correlating NAMS data with flight progress strips. A thermometer and a pressure gauge are used for NAMS as meteorological sensors to obtain data on the atmosphere. Rough estimates of indicated altitude are obtained automatically on the basis of simple equations using observed parameters by NAMS.

This paper deals with a method for estimating the indicated altitude using meteorological data obtained by NAMS and some results of the estimation method based on empirical data.

Terminal Radar Numeric Display System has been developed for the requirement of a digital radar display employing SSR data at airports with medium traffic density.

It gives SSR mode A/C numeric data tags to the corresponding radar blips on the display, and a digital map. The system consists of the beacon video digitizer (BVD), which detects target data from SSR raw video using a sliding window method, the target data processor and display control unit, which use microprocessors with fixed programs in read only memories for display data processing, and the data display subsystem which is similar to data entry and display subsystem of ARTS.

The system features high reliability and high availability because of its simple system structure and self-monitoring functions.

The evaluation tests are made on its functions and statistical data are obtained from actual radar signals using its BVD. The result showes that reasonable operation can be expected as a new system.

A major problem with the Instrument Landing System (ILS) Glide Slope is the dependence of performance on the terrain condition, since the Glide slope utilizes the ground image. Deep snow elevates the effective ground level and affects its performance.

The relations of snow depth and the Glide Slope performance were measured for two types of ILS Glide Slopes, i.e., the Null reference system and the Capture effect system, with a 55 m high far field monitor at the new Akita airport.

The results show that (1) the Null reference path angle increases at a rate of 0.021 degree per 10 cm of snow and the path width increases at a rate of 0.025 degree per 10 cm, (2) the Capture effect path angle increases at a rate of 0.025 degree per 10 cm of snow and the path width decreases at a rate of 0.011 degree per 10 cm, and (3) the Near field monitor is about 3 times as oversensitive as the far Bureau.

The effects of sky wave components and mountain range propagation on the position fix errors of the Decca System are studied here based upon two observations. The position data are obtained by using a Decca Receiver (MS-3A) and a Decca Processor (DP-80) on the Kantoh Decca Chain.

The result obtained by fixed observation at Mitaka-city, Tokyo for 8 months from July 1981 gives comparatively large fluctuations in the night time due to the sky wave effects. The G-P pair indicates a high accuracy and stable position-fixing. RMS rerative errors of G-P, R-G and P-R pair are 169, 296 and 630 meters in the night time and they are 42, 108 and 150 meters in the day time, respectively.

The results obtained by mobile observations in the day time for 4 days along the coast line of the IZU-Peninsula give rather high position fix errors which seem to be caused mainly by the effect of mountains range propagation. On the west coast of the IZU-Peninsula, the mean deviation is approximately 400 meters whose maximum amount to about 900 meters. On the east coast, they are approximately 100∼200 meters in deviation and about 400 meters at the maximum.