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豪州での小型自動着陸実験(ALFLEX: Automatic Landing Flight Experiment)で、飛行経路の実時間監視のために、トラッキング・レーダが使用された。監視精度向上のための精密な較正を行った後、懸吊飛行試験において、レーザ・トラッカ取得測位データとの比較により、トラッキング・レーダによる測位の精度評価を行った。その結果、実時間監視用として充分な精度であることが確認できた。さらに、自動着陸実験においても測位精度評価を行い、実時間監視が確実に行われていたことを確認した。, ALFLEX (Automatic Landing Flight Experiments) were conducted at Woomera airport in Australia in 1996. In these experiments, an ALFLEX vehicle is lifted by helicopter, released at an altitude of around 1,500 meters and landed on a runway automatically. A tracking radar was employed as a real-time flight path monitor of the vehicle during the experiments. The positioning accuracy of the tracking radar was evaluated by comparing it with that of the laser tracker in the flight tests. In conclusion, it was confirmed that the tracking radar used met the accuracy requirements for a real-time monitor system for ALFLEX., 資料番号: AA0001972000, レポート番号: NAL TM-749

東京水産大学海洋システム工学講座

東京水産大学海洋システム工学講座, 東京水産大学研究練習船神鷹丸

GPS搬送波位相干渉法による精密測位は、従来測地測量などの静止基線解析の分野で幅広く応用されているが、時々刻々と変化する基線に対しては適用が難しいとされてきた。ところが、近年、搬送波に内在する未知数(アンビギティ)を実時間で解くアルゴリズム(On-The-Fly(OTF)アルゴリズム)が多くの研究者によって開発され、移動体に対する精密測位も可能となってきた。本報告では、航技研で独自に開発した新しいOTFアルゴリズムを提案し、様々な実験による実証例を示す。GPS搬送波を用いた移動体の精密測位は、キネマティックGPS(KGPS)と呼ばれるが、航空技術研究所では独自のOTFアルゴリズムを核とするKGPSソフトウェア、KINGSを開発し、その性能評価を研究用航空機ドルニエ228を用いて行った。その結果、基線長20km以内、可視衛星5衛星以内の場合に、98%以上の確率でほぼ瞬時にアンビギティを解くことができた。アンビギティが正しく解けた場合の測位精度は約10cm(3σ)である。, Precise positioning using GPS carrier phase measurement has been widely used in static applications, i.e., geodetic surveying. However, it can also be applied to the precise positioning of a moving platform if an ambiguity contained in the GPS carrier phase measurement is resolved during the motion. The technique to resolve the ambiguity on the way/fly, which is called the OTF (On-The-Fly), has been investigated by many authors. In this paper, a new OTF algorithm is proposed and its feasibility for several kinds of applications is demonstrated. The differential GPS positioning using carrier phase measurements is called Kinematic GPS (KINGS). The Kinematic GPS Software, KINGS, in which the OTF is the most significant algorithm, was developed and its performance was evaluated by conducting a lot of flight experiments using a research aircraft of the National Aerospace Laboratory (NAL). As a result, the correct ambiguity was resolved nearly instantaneously with more than 98 percent probability when the distance between the aircraft receiver and the ground reference receiver was less than 20 km, and five or more satellites were observed. Once the ambiguity was resolved, the aircraft position was determined within 10 cm (3 sigma)., 資料番号: AA0001666000, レポート番号: NAL TR-1357T

航空宇宙技術研究所 宇宙開発事業団 28 Feb. 1997 Sydney, National Aerospace Laboratory. National Space Development Agency of Japan 28 Feb. 1997 Sydney Australia, オーストラリアで行ったALFLEX(小型自動着陸飛行実験)において、飛行経路の実時間モニタに追尾レーダを用いた。最初の懸吊飛行試験において、レーザ追尾装置による位置データと比較して取得した校正データを追尾レーダのシステムに組み込んだ。校正した追尾レーダの測位精度を、その後の懸吊飛行試験においてレーザ追尾装置と比較して評価し、追尾レーダが実時間モニタに充分な測位精度を有することを確認した。さらに、自由飛行試験における精度を評価し、追尾レーダで取得したデータの測位精度を向上させるための補正データを得た。, A tracking radar was used for real time flight path monitoring of ALFLEX (Automatic Landing Flight Experiment) at Australia. Calibration data, compared with position data by a laser tracker, were obtained at the first hanging flight test, and the calibration data were installed in the tracking radar. After calibration, the positioning accuracy of tracking radar was evaluated in comparison with the laser tracker in hanging flight tests. The results confirmed that the accuracy was satisfactory for real time monitoring. In addition, the accuracy was evaluated in free flight tests and the post correction data of the tracking radar were derived., 資料番号: AA0001565014, レポート番号: NAL SP-39T

航空宇宙技術研究所所有の実験用航空機ドルニエ機Do228(Dornier 228-200)を使い、航法系機器精度評価を行うための飛行実験が1990年10月より仙台空港ターミナルエリア内で実施されている。船舶や自動車で既に使用され将来の航法装置の1つとして有望視されているGPS(全世界測位システム)受信装置がDo228に搭載され、進入着陸を中心とした飛行評価実験が行われた。Do228に搭載されたGPS受信装置はC/Aコード、1チャンネルの航空用GPS受信装置であるが、地上固定局で測位・評価した補正量を受信すると実時間のデイファレンシャルGPS(DGPS)を行うことができる。DGPSは地上固定局と機上局の2つの受信装置の共通誤差を打ち消すことで、単独で測位するより精度の高い測位を行える。GPSの測位精度はGPS受信装置自体の精度ばかりでなく、GPS衛星の配置、衛星からの電波が通過する対流圏の状態、そして人工的に精度を劣化させるSA(選択利用性誤差)の影響により大きく変化する.実験の進入着陸時に発生するこれらの誤差要因の影響下におけるGPS受信装置の精度評価を行うために仙台空港で飛行実験を実施しているが、本報告書では1990年10月-1991年12月までの4回(合計21フライト)の実験を取り上げ、レーザ・トラッカーを基準としたGPS測位精度についてまとめたあと、その評価について述べる。評価方法は、着陸進入時のGPS受信装置の出力位置を、SA環境下で(1)単独測位、(2)DGPS測位、および(3)SA無しでの単独測位の3つのグループに分け、測位精度へのDGPSによる影響とSAによる影響を調べた。その結果、SA環境下ではDGPS測位を行うと測位精度は約40m改善され、またSAによる測位精度への影響は約55mであることが判明した。SA無しの状況での単独測位精度はSA環境下でのDGPS測位精度より良い結果が得られた。, Navigation systems have been tested with a Dornier 228-200 (Do-228), experimental research airplane of National Aerospace Laboratory (NAL) at Sendai airport, Japan. A C/A (Clear and Aquisition) code single channel Global Positioning System (GPS) receiver (Rockwell/Collins Navcore 1) was installed in the Do-228. This paper describes GPS/DGPS accuracies during approach and landing of the aircraft. All data in which GDOP (Geometric Dilution Of Precision) is less than five are divided into three cases: (1) stand-alone navigation with SA; (2) differential navigation with SA; and (3) stand alone navigation without SA tested on January 1991. Stand-alone accuracy is 75 meters and differential accuracy is 35 meters. Although stand-alone navigation accuracy under no SA is 20 meters, that is because the receiver's specific errors are more than common errors. The effectiveness of DGPS under SA was demonstrated flight experiments., 資料番号: AA0004243000, レポート番号: NAL TR-1230

航空宇宙技術研究所(NAL)の実験用航空機ドルニエ機搭載の航法装置であるGPS(全地球的位置決めシステム)受信装置と地上ベース・ステーションのGPS受信装置との間のデータ・リンクを完成させ、高精度航法が可能とされるディファレンシャルGPS(DGPS)を行い、日本ではじめて航空機による実時間DGPSを実現させた。この搭載GPS受信装置の測位精度確認のため、飛行試験での評価の前に、地上の固定点における測位評価実験を行った。この測位実験において搭載およびベース・ステーションのGPS受信装置の受信アンテナを共通にすることにより、両受信装置の測位における不確定要素を同じにし、測位結果のより正確な比較を行った。本報告ではこの固定点における搭載GPS受信装置単独での測位とDGPSでの測位との比較、検討を行いその位置精度について述べる。また、DGPS測位により意図的なGPS衛星情報の誤差、すなわち選択利用性(SA)誤差の除去が可能であることを実験的に明らかにした。, A real-time Differential Global Positioning System (DGPS), incorporating a ground-to-air data link system, was developed for the National Aerospace Laboratory (NAL) Dornier 228-200 flight research airplane. Preliminary ground tests were conducted to evaluate the system's position accuracy prior to flight testing. The onboard and ground GPS receivers used the same antenna in order to avoid unknown common errors (e.g., antenna system and troposheric delays), and to enable comparision of the optimal case of differential operation. The GPS position accuracies of the stand-alone and differential modes are compared, with results showing the differential mode improves position accuracy and eliminates Selective Availability (SA) errors., 資料番号: AA0004137000, レポート番号: NAL TM-649

We have measured the usable time and got position fixes from overseas fixed stations for the past three years in order to evaluate the positioning accuracy of GPS. We were able to receive positioning signals from only 6 satellites until 1989, but in October 1990, 15 GPS satellites became available. And the orbits of satellites have been corrected. The usable time was 7～9 hours until 1989, but it came to be more than 18 and a half hours in 1990. Then we were generally able to get position fixes by 3D (three-dimensional positioning) and the high level of 2D3 (two-dimensional positioning with three satellites). Therefore, position fixes of 2D2 (two-dimensional positioning with two satellites) became hardly necessary. The accuracy of position fixes went down once in 1989. In 1990, the standard deviations of D. lat (difference of latitude) and Dep (departure) were kept less than 45 meters. We may conclude that in spite of selective availability, the accuracy has been improved owing to the increasing number of GPS satellites and the correction of thier orbits., 長崎大学水産学部研究報告, v.70, pp.19-28; 1991

In recent years, the number of GPS satellites has been increasing, and this system became operational with 15 satellites in October, 1990. In addition, its selective availability has been possible since March 25th, 1990. Thus, we measured the usable time and got position fixes from our fixed station at Nagasaki University in order to evaluate the positioning accuracy for three days in each of September and October, 1990. The usable time was about 19 and a half hours, which was two times longer than that with 6 satellites. Especially, position fixes of 3D (three-dimensional positioning) occupied 12 hours of the usable time. Despite the selective availability, standard deviations of D. lat (difference of latitude) and Dep (departure) were kept less than 20 meters due to increasing high level measurements, and the maximum positioning errors were 60～65 meters. We may conclude that the accuracy of this system has been improved because the standard deviation became so small as to be under 20 meters.

We measured the usable time and got position fixes from two foreign fixed stations in order to evaluate the positioning accuracy of GPS in terms of the difference in location between the stations. We received positioning signals from 6 satellites and also obtained position fixes by means of two satellites. The usable time measured at Honiara and Sydney was shorter than that measured at Nagasaki, but three-dimensional positioning accounted for 40～50% of the total time and most of the data were on a high level. We eliminated not a few data in both stations because their errors were larger than 1 nautical mile. These data accounted for 10% of the total number, especially in Honiara. There were no obvious locality differences found in 2D3 (two-dimensional positioning by means of three satellites) and 3D (three-dimensional positioning), i.e. the positioning errors in them were smaller than 0.1 nautical mile. But we observed that there were some locality differences in the usable time and the arrangement of the satellites., 長崎大学水産学部研究報告, v.67, pp.21-29; 1990

We measured the usable time and took position fixes from three fixed stations in our country in order to evaluate the positioning accuracy of GPS, first, by the difference in the time of the year and, second, by the difference in location between the stations. In the case of the former, the time zone of position fixes varied with the time of the year and there were a little differences of the accuracies of position fixes except 3H (three-dimensional high level positioning). In the case of the latter, there were not obvious locality differences in 3D (three-dimensional positioning). But the positioning errors and number of data varied on each level in 2D (two-dimensional positioning), although the positioning errors were smaller than 0.1 nautical mile. The standard deviations of Dep. (departure) were larger than that of D.lat. (difference of latitude), and varied widely to the east and the west. But we observed that the standard deviations were smaller than 100 meters., 長崎大学水産学部研究報告, v.65, pp.45-53; 1989