JP2004170151A

JP2004170151A - Displacement detector

Info

Publication number: JP2004170151A
Application number: JP2002334224A
Authority: JP
Inventors: Kenji Itani; 健二井澗
Original assignee: Furuno Electric Co Ltd
Current assignee: Furuno Electric Co Ltd
Priority date: 2002-11-18
Filing date: 2002-11-18
Publication date: 2004-06-17

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement detector for performing evermore optimum displacement detection even if the number of receivable satellites differs, performing displacement detection of positioned points even if positioning satellites required for positioning are small in number, and providing higher positioning accuracy when signals are receivable from positioning satellites exceeding a number required for positioning. <P>SOLUTION: Doppler shift frequency of signals transmitted from two satellites (a) and (b) is observed at a reference point (f) and a positioning point (m) to find an observation double difference of the Doppler shift frequency by the observation. A calculation double difference of the Doppler shift frequency is found based on the positions of the reference point (f) and positioning point (m), and on the positions and speeds of the two satellites (a) and (b). The relative displacement of the positioning point to the reference point is detected according to whether or not the two double differences are shifted from each other. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
この発明は、測位用衛星からの信号を受信して測位点の変位を検出する変位検出装置に関するものである。
【０００２】
【従来の技術】
従来、例えば傾斜地の地すべりやダムの変形を監視するなど、何らかの変位を監視するためにＧＰＳ測位を利用した変位検出装置が用いられている（例えば、特許文献１参照。）。
【０００３】
このようなＧＰＳ衛星からの信号を受信して測位点の変位を監視する装置は、一定時間周期毎に、または所定のタイミングで測位点の測位を行い、測位点の計時的な変位の傾向や急激な変位を監視するように構成している。
【０００４】
【特許文献１】
特開平６−１６０５０９号公報
【０００５】
【発明が解決しようとする課題】
前記ＧＰＳ測位は、基準とするＧＰＳアンテナと、測位点に設けたＧＰＳアンテナとの相対位置を求めるものであるが、その測位を行うためには、最低４つのＧＰＳ衛星からの信号を受信する必要がある。ところが、ＧＰＳ測位により変位検出を行う適用分野では必ずしも天空の視界が開けているとは限らない。例えば傾斜地の地すべりを監視するような環境では、傾斜地自体の地形によって天空の一部が常に遮られているため、４つ以上のＧＰＳ衛星からの信号を受信できない時間帯が生じる確率が高くなる。特に北側の斜面では、ＧＰＳ衛星の軌道の関係から受信可能な衛星数が元々少なく、測位のできない時間帯が生じやすい傾向にある。このような変位検出のできない時間帯が生じる条件では、連続的な監視が完全には行えないことになる。また、完全に連続した監視が要求される場合には、その適用範囲が限られてしまうことになる。
【０００６】
一方、ＧＰＳ測位においてマルチパスは測位精度劣化の一因である。すなわち、ＧＰＳ衛星からＧＰＳアンテナに直接入射する直接波と、何らかの電波反射体で反射して入射する反射波とが重畳されて、観測キャリア位相が変動し、測位結果に誤差が生じる。一般的には、マルチパスを取り除くために、反射波の到来しやすい方向からの入射を遮断する部材を設けるなどしてアンテナの構造を工夫しているが、装置のサイズが大型化するという欠点があった。また、キャリア位相の追尾は、Ｃ／Ａコード位相の追尾と協調して行われるので、観測キャリア位相の精度はＣ／Ａコード位相の精度に影響を受ける。そのため、狭い時間幅で相関を求めて、マルチパスによるＣ／Ａコード位相の誤差を低減するとともに、キャリア位相追尾のためのループフィルタの帯域幅を狭めることなどによって、マルチパスによる測位誤差を低減することができる。しかし、このような相関処理を行うと、全体の消費電力が増大してしまい、例えば太陽電池を電源とするような場合に問題となる。
【０００７】
前述した変位の監視は、通常動かない点で測位を行うので、マルチパスによる誤差の様子はＧＰＳ衛星の移動と測位点周りの電波反射物の配置によって決まる。ＧＰＳ衛星の角速度は１分当たり約０．５度であり、測位点から見てその動きは非常にゆっくりしており、また電波反射体も動かないので、マルチパスによる観測キャリア位相の誤差分の変化は非常に緩慢である。実際のいくつかの環境で観測してみると、キャリア位相の二重差は、ランダムノイズにより短周期で約±０．０５レーン（±１ｃｍ）変動するとともに、マルチパスにより１〜１０分程度の長時間周期で変動する。したがって、短時間周期のランダムノイズは比較的短時間の時定数で平均化処理を行うことによって取り除けるが、マルチパスによる変動は１〜１０分程度以上の長時間にわたる平均化処理を行わなければ取り除けない。したがって、このような長時間にわたる平均化を行わずに、マルチパスによる長周期の測位誤差の変動を含んだまま監視を行うか、長時間にわたる平均化を行って、測位点の短時間の変位を無視した監視を行うことになってしまう。
【０００８】
前者の必要衛星数に満たない状況で変位検出不能になるという問題と、後者のマルチパスによる測位誤差の増大および応答性の低下の問題は、いずれも測位用衛星からの信号を如何にうまく利用するかに関わる。また、これらの問題は、傾斜地やダムなど定常時に静止しているものを対象として測位点の変位を検出する場合に限らず、複数の観測点の相対変位を監視する場合に一般に生じる問題である。
【０００９】
そこで、この発明の目的は、受信可能な衛星数が様々に異なっても常に最適な変位検出を行えるようにすることにある。
【００１０】
また、この発明の他の目的は、測位のために必要な測位用衛星の数が少ない場合でも測位点の変位検出を可能とし、また測位に要する数以上の測位用衛星からの信号が受信できる状態では、より高い測位精度が得られるようにした変位検出装置を提供することにある。
【００１１】
【課題を解決するための手段】
この発明は、複数の測位点で、複数の測位用衛星から送信された信号を受信して該測位点の変位を検出する変位検出装置において、少なくとも２つの測位用衛星から送信された信号のドップラシフト周波数または単位時間あたりのキャリア位相変化量を各測位点で観測して、複数の測位点のうち所定の測位点を基準とし、該基準点と他の測位点での観測による、ドップラシフト周波数または単位時間あたりのキャリア位相変化量から、ドップラシフト周波数または単位時間あたりのキャリア位相変化量の観測二重差を求める手段と、基準点と測位点の位置、前記少なくとも２つの測位用衛星の軌道情報および時刻に基づいて、ドップラシフト周波数または単位時間あたりのキャリア位相変化量の計算二重差を求める手段と、該計算二重差と前記観測二重差のずれにより、基準点に対する測位点の相対的な変位を検出する手段とを備えたことを特徴としている。
【００１２】
この構成により、２つの測位用衛星からの信号しか受信できない場合でも測位点の変位検出を可能とする。もっとも、測位点に対する２つの測位用衛星の配置によっては変位検出精度が低下する。場合によっては、変位検出不可能な変位方向も生じるが、変位検出不可能となる確率は低く、しかも４つ以上の測位用衛星が必要な従来の場合に比べて稼動率は大幅に改善される。
【００１３】
また、この発明は、少なくとも２つの測位用衛星から送信された信号のキャリア位相を各測位点で観測して、複数の測位点のうち所定の測位点を基準とし、該基準点と他の測位点での観測によるキャリア位相からキャリア位相の観測二重差を求める手段と、基準点と測位点の位置、前記２つの測位用衛星の軌道情報および時刻に基づいてキャリア位相の計算二重差を求める手段と、該計算二重差と前記観測二重差のずれにより、基準点に対する測位点の相対的な変位を検出する手段とを備えたことを特徴としている。
【００１４】
このようにキャリア位相の観測二重差と計算二重差とのずれによって測位点の変位を検出することによって、２つの測位用衛星からの信号が受信できれば測位点の変位検出が可能となり、稼働率が大幅に改善される。
【００１５】
また、この発明は、前記測位点の変位前の位置から該測位点を通る傾斜線を下る方向にのびる線と前記観測二重差による等位相差面とから測位点の変位後の位置を推定する手段を備えたことを特徴としている。これにより、測位点の変位の有無だけでなく、その変位量も求められるようにする。
【００１６】
また、この発明は、複数の測位用衛星からの信号を受信し、基準とする測位用衛星とその他の各測位用衛星とを組とする観測キャリア位相差を求める手段と、評価対象外の測位用衛星を用いて測位した測位点の位置と、前記基準とする測位用衛星および評価対象とする測位用衛星の軌道情報と時刻とに基づいて、基準とする測位用衛星と前記評価対象の測位用衛星とを組とする計算キャリア位相差を求める手段と、前記評価対象の測位用衛星について、前記観測キャリア位相差と前記計算キャリア位相差とのずれを求めるとともに、該位相差のずれに基づいて、測位精度に関する評価を行い、該評価の高い測位用衛星の前記観測距離に基づいて測位点の測位を行う手段とを備えたことを特徴としている。
【００１７】
このように、受信可能な測位用衛星の数が測位に必要な数より多い場合に、評価対象とする測位用衛星の測位精度に与える影響度を、それ以外の測位用衛星を用いて評価する。このことにより、最適な測位用衛星を用いて高精度な測位および微小な変位を的確に検出できるようにする。
【００１８】
また、この発明は、測位に用いた前記測位用衛星の、測位点に対する配置によって定まる測位精度指数に応じて、前記評価を補正するようにする。これにより、評価対象以外の、測位に用いる測位用衛星の如何なる配置によっても、測位精度に関する評価を等しく行えるようにする。
【００１９】
【発明の実施の形態】
この発明の実施形態である変位検出装置の構成を図１〜図６を参照して説明する。
図１は例えば傾斜地の土砂崩れの監視を行うシステム全体の構成を示すブロック図である。図１において２ａはＧＰＳアンテナ、１ａはＧＰＳ受信機である。ＧＰＳ受信機１ａはＧＰＳアンテナ２ａの位置で複数のＧＰＳ衛星からの信号を受信する。３ａは測位点側に設けた無線機、４ａはその送受信アンテナである。これら１ａ，２ａ，３ａ，４ａによって１組の観測装置を構成している。１ｂ〜４ｂは同様に他の観測装置を構成している。１ｍ〜４ｍについても同様である。このような複数の観測装置を傾斜地の所定位置に設置している。
【００２０】
また、６はセンタ側の無線機、５はその送受信アンテナである。このセンタ側の無線機６は複数の観測装置側の無線機３ａ，３ｂ，・・・３ｍとの間でデータ通信を行う。８はＧＰＳ受信機、７はＧＰＳアンテナである。ＧＰＳ受信機８は主としてＧＰＳタイム（ＧＰＳ測位系で用いる時刻）に同期した所定のタイムスケジュールで複数の観測装置側の無線機との間でデータ通信を行う際の時刻同期信号を得るために備えている。９はデータ回収処理装置であり、複数の観測装置で観測された、各測位用衛星毎および各時刻毎のキャリア位相およびドップラーシフト周波数の観測データを回収し、各観測装置の測位点の変位を検出する。また、必要に応じてその検出結果を外部へ送信する。
【００２１】
図２は、図１に示した複数の各観測装置のうち、一つのＧＰＳ受信機の構成を示している。
ここで、１２はＧＰＳアンテナ１の受信信号を中間周波信号に周波数変換し、所定周期でサンプリングし、順次デジタルデータ列に変換するダウンコンバータである。受信信号処理部１３は、Ｃ／Ａコードの相関器およびキャリア信号の相関器を、それぞれ複数チャンネル分備えている。ＣＰＵ１４は各ＧＰＳ衛星からの受信信号のキャリア位相を観測し、通信インターフェース１７を介して無線機へ出力する。ＲＯＭ１５にはＣＰＵ１４の実行すべきプログラムを予め書き込んでいる。ＲＡＭ１６は演算処理の際ワーキングエリアとして用いる。
【００２２】
図３は観測装置側のＧＰＳ受信機の処理内容を示すフローチャートである。処理の流れを大きく分けると、まず各ＧＰＳ衛星からの受信信号のサーチを行い、受信信号のＣ／Ａコードおよびキャリア位相の捕捉追尾を行う（ｓ１）。そして、各ＧＰＳ衛星からの受信信号の観測キャリア位相を求める（ｓ２）。この観測キャリア位相のデータを時刻データおよび衛星番号と共に１組のデータとして無線機へ送信する（ｓ３）。無線機は、これらのデータをセンタ側の無線機へ無線送信する。以上の処理を各ＧＰＳ受信機が繰り返すことによって、センタ側のデータ回収処理装置９は、各観測装置の各時刻・各衛星についての観測キャリア位相のデータを収集する。
【００２３】
図４はセンタ側のデータ回収処理装置９での処理内容を示すフローチャートである。この図４に示すように、まず処理対象とする観測装置のＧＰＳ受信機で受信された衛星数が、キャリア位相二重差による３次元測位可能な衛星の数（４つ）以上であれば、それらの衛星からの信号を受信して求められた観測によるキャリア位相に基づいて測位点の測位を行う（ｎ１→ｎ２）。具体的には、複数の観測装置のうち所定の観測装置のＧＰＳアンテナを基準点とするキャリア位相の二重差を求め、その整数バイアスを公知の整数バイアス決定法により決定し、基準点に対する相対測位を行う。そして、前回またはそれ以前までに求めた位置から今回求めた測位点の位置のずれ量を検出する（ｎ３）。
【００２４】
また、受信された衛星の数が、通常のキャリア位相二重差による３次元測位可能な衛星の数（４つ）に満たない時、以降で述べる方法により測位点のずれの有無を検出する（ｎ４）。
以上の処理を全ての観測装置の測位点について行い、その結果を出力する（ｎ５）。この結果出力の処理では、測位点のずれ量が予め定めた閾値を超えた時、その測位点が位置ずれしたものと見なしてその警報出力を行う。
【００２５】
図５は図４に示したステップｎ４の処理内容を示すフローチャートである。まず、観測した２つの衛星についてのドップラーシフト周波数の二重差（観測二重差）を求める（ｎ１１）。続いて、その２つの衛星についてドップラーシフト周波数の計算上の二重差を求める（ｎ１２）。すなわち、測位点の概略位置とその時点での２つの衛星の軌道情報と時刻とから２つの衛星の移動速度を求め、測位点に対する２つの衛星の幾何学的配置によりドップラーシフト周波数の計算二重差を求める。
【００２６】
ここでドップラーシフト周波数の計算二重差について図６を参照して説明する。
２つの衛星ａ，ｂが存在し、基準点をｆ、測位点をｍとし、単位時間で、衛星ａがａ１からａ２へ、また衛星ｂがｂ１からｂ２へ移動するものとすると、測位点ｍから見た衛星ａのドップラーシフト周波数ｄ_ｍ ^ａは次のように表せる。
【００２７】
ｄ_ｍ ^ａ＝ｌ_ｍ ^ａ２−ｌ_ｍ ^ａ１
また、測位点ｍから見た衛星ｂのドップラーシフト周波数ｄ_ｍ ^ｂは次のように表せる。
【００２８】
ｄ_ｍ ^ｂ＝ｌ_ｍ ^ｂ２−ｌ_ｍ ^ｂ１
更に、基準点ｆから見た衛星ａ，ｂのそれぞれのドップラーシフト周波数ｄ_ｆ ^ａ，ｄ_ｆ ^ｂは次のように表せる。
【００２９】
ｄ_ｆ ^ａ＝ｌ_ｆ ^ａ２−ｌ_ｆ ^ａ１
ｄ_ｆ ^ｂ＝ｌ_ｆ ^ｂ２−ｌ_ｆ ^ｂ１
ここで、ｌ（エル）は衛星−受信点間距離であり、下付き添え字が受信点を、上付き添え字が衛星をそれぞれ識別する記号である。
【００３０】
また、測位点ｍで求めたドップラーシフト周波数の衛星間一重差∇ｄ_ｍは、
∇ｄ_ｍ＝ｄ_ｍ ^ａ−ｄ_ｍ ^ｂ
で求められる。
【００３１】
同様に、基準点ｆで求めたドップラーシフト周波数の衛星間一重差∇ｄ_ｆは、
∇ｄ_ｆ＝ｄ_ｆ ^ａ−ｄ_ｆ ^ｂ
で求められる。
【００３２】
従ってドップラーシフト周波数の二重差Δ∇ｄは、
Δ∇ｄ＝∇ｄ_ｍ−∇ｄ_ｆ
で求められる。
前記ドップラーシフト周波数の計算二重差は以上のようにして求める。
【００３３】
さて、図５に戻って、その後、上記観測二重差と計算二重差の差を求め、二重差同士の差に有意差があるか否かを判定する（ｎ１３）。その値が所定の閾値ε以上であれば、測位点の位置ずれが生じたものと見なし（ｎ１４）、ε未満であれば測位点の位置ずれは無かったものと見なす（ｎ１５）。
【００３４】
なお、上述の「ドップラーシフト周波数」に代えて、「単位時間あたりのキャリア位相変化量」を用いてもよい。
【００３５】
次に、第２の実施形態に係る変位検出装置の構成を図７を参照して説明する。
第１の実施形態で示した変位検出装置と異なるのは、受信された衛星の数がキャリア位相二重差による３次元測位可能な４つに満たない場合の処理（図４のステップｎ４に相当する処理）として、キャリア位相の二重差を求めて行う。まず図７に示すように、観測した２つの衛星についてのキャリア位相の二重差（観測二重差）を求める（ｎ２１）。続いて、その２つの衛星についてキャリア位相の計算上の二重差を求める（ｎ２２）。すなわち、測位点の概略位置とその時点での２つの衛星の軌道情報と時刻とから２つの衛星の位置を求め、測位点に対する２つの衛星の幾何学的配置によりキャリア位相の計算二重差を求める。その後、上記観測二重差と計算二重差の差をずれ量として求める（ｎ２３）。そして、このずれ量が有意な値であるか否かを判定する（ｎ２４）。その値が所定の閾値ε以上であれば、測位点の位置ずれが生じたものと見なし（ｎ２５）、ε未満であれば測位点の位置ずれは無かったものと見なす（ｎ２６）。
【００３６】
なお、第１・第２の実施形態において、３つの衛星からの信号が受信されていれば、もう１組の２つの衛星について同様にして二重差同士の差を求める。そして、２組の二重差同士の差のいずれか一方に有意差があれば「ずれ有り」と見なす。
【００３７】
次に、第３の実施形態に係る変位検出装置について図８および図９を参照して説明する。
第１・第２の実施形態では、単に測位点の変位の有無を検出するだけであったが、観測装置の設置場所の環境によっては、受信可能な衛星の数がキャリア位相の観測二重差による３次元測位可能な衛星数に満たない場合であっても、その変位の量を推定することができる。例えば、図９の（Ｂ）は測位点ｍの設置位置周りの状況を斜視図として示しているが、このように傾斜地に観測装置を設けた場合、その測位点が土砂崩れなどによって変位する方向は通常、傾斜線に沿った方向である。ｍは変位前の位置、ｍ′は変位後の位置の例を示している。
【００３８】
図９の（Ａ）は、２つの衛星を用いて求められるキャリア位相の計算二重差と観測二重差の例について示している。変位前の測位点の位置ｍはキャリア位相の二重差による双曲面をなす等位相差面（以下「位置面」という。）上の所定の位置に存在する。変位前であれば、この計算二重差による双曲面をなす位置面と観測二重差による位置面とは一致しているはずである。土砂崩れなどによって測位点がｍからｍ′に変位すれば、このｍ′は変位後の観測二重差による位置面のどこかに存在することになる。すなわち２つの衛星を用いただけではｍ′がこの観測二重差による位置面の何れかの位置にあることが分かるだけであり、その３次元位置までは求められない。
【００３９】
しかし、図９の（Ｂ）に示したように、測位点の変位は通常、傾斜線に沿って生じるので、変位前の観測および計算により求められている位置ｍから傾斜線を下る方向に伸ばした直線と観測二重差による位置面との交点が変位後の位置ｍ′として推定できる。このｍとｍ′との距離が変位量である。このようにすれば、受信可能な衛星数が２つであっても変位量を求めることができる。なお、上記傾斜線を下る方向にのびる線を直線とせずに、地形に応じた曲線としてもよい。
【００４０】
図８は上述の処理内容を示すフローチャートである。まず、２つの衛星について観測したキャリア位相から観測二重差を求める（ｎ３１）。また、その２つの衛星についてキャリア位相の計算二重差を求める（ｎ３２）。そして、この観測二重差と計算二重差の２つの位置面と、傾斜線方向の情報とから変位量を求め、それを出力する（ｎ３３→ｎ３４）。上記観測二重差と計算二重差が一致すればもちろん変位量は０である。
なお、各観測装置を設置した位置の傾斜線の情報は、地形図データと観測装置の位置とに基づいて計算で求めるか、各観測装置毎に予め入力しておく。
【００４１】
次に、第４の実施形態に係る変位検出装置の構成を図１０〜図１２を参照して説明する。
この第４の実施形態は、キャリア位相二重差による３次元測位に要する衛星数を超える数の衛星からの信号が受信された場合の処理を特徴としている。図１０は図１に示したデータ回収処理装置９で行われる処理のうち、各観測装置についての測位のための処理内容を示すフローチャートである。但し、ここでは１つの観測装置についての処理を示している。
【００４２】
まず、受信された衛星の数がキャリア位相の二重差による３次元測位に必要な数（４つ）を超える数であれば、それらの各衛星について測位精度に与える影響度の評価値を求める（ｎ４１→ｎ４２）。その後、評価値に応じて、測位精度が最も高くなるための４つの衛星を決定し、それに基づいてキャリア位相二重差を３組求め、基準点に対する相対測位を行う（ｎ４３→ｎ４４）。
【００４３】
受信された衛星の数が４つであれば、その４つの衛星を用いて測位を行い、４つ未満であれば第１〜第３の実施形態で示した方法により変位検出を行う（ｎ４５）。
【００４４】
図１１は、図１０のステップｎ４２の処理手順を示すフローチャートである。まず、５つ以上の衛星のうち最も仰角の高い（天頂付近の）衛星を基準衛星とし、評価対象の衛星と基準衛星とを組とする観測キャリア位相の二重差を求める（ｎ５１→ｎ５２）。そして、評価対象以外の衛星により求めた測位点の位置、その時刻での基準衛星の位置および評価対象衛星の位置より、計算上のキャリア位相の二重差を求める（ｎ５３）。続いて、後述する衛星配置による測位精度指数を求める（ｎ５４）。そして、上記観測キャリア位相の二重差と計算キャリア位相の二重差との差と、測位精度指数とから評価値を決定する（ｎ５５）。例えば二重差同士の差が小さいほど評価値を高め、測位精度指数が小さいほど（測位精度が高いほど）、二重差同士の差に基づく評価値の変動幅を小さくする。従って測位精度指数が大きくて、二重差同士の差が小さいほど評価値は高まり、同じく測位精度指数が大きくて、二重差同士の差が大きいほど評価値は下がる。
【００４５】
次に、上記衛星配置による測位精度指数について図１２を参照して説明する。図１２において、（Ｓａ−Ｓｒ）は２つの衛星Ｓａ，Ｓｒの組によって生じるキャリア位相の位置面と水平面との交差により生じる線（位置線）である。また、（Ｓｂ−Ｓｒ）は２つの衛星Ｓｂ，Ｓｒの組によって生じるキャリア位相の位置面と水平面との交差により生じる線（位置線）である。ここで太線はある位置線、細線はそれに隣接する１波長分離れた位置線である。このように、２組の位置線の交差によって菱形部分が生じるが、その菱形に外接楕円を描いた時、短軸方向の精度指数が最も良好であり、長軸方向の測位精度は最も悪い。これを位置線の間隔（約２ｃｍ）を１とした時の係数を精度指数とすると、この例では短軸方向の精度指数が１．１、長軸方向の精度指数が３．３程度である。
【００４６】
ここで図１２の（Ｂ）に示すように、基準衛星Ｓｒと評価対象の衛星Ｓｅによって生じる位置線に上記楕円を重ねる。この楕円の中心から位置線の間隔方向へのばした径が、その位置線に対する精度指数を表すことになる。この例では約２．５である。この精度指数を定量的に求めるには次の関係式により求めればよい。
【００４７】
ここで、ｉ番目の衛星から測位点までの距離をｒｉ
測位点の座標を（ｘｏ，ｙｏ，ｚｏ）、
ｉ番目の衛星の位置を（ｘｉ，ｙｉ，ｚｉ）とし、
測位点から見た各衛星へのｘ，ｙ，ｚ方向の方向余弦を、
αｉ＝（ｘｉ−ｘｏ）／ｒｉ
βｉ＝（ｙｉ−ｙｏ）／ｒｉ
γｉ＝（ｚｉ−ｚｏ）／ｒｉ
とおき、
【００４８】
【数１】

【００４９】
とすれば、重み係数行列は、共分散行列として
【００５０】
【数２】

【００５１】
で表される。
【００５２】
そして、衛星配置による幾何学的精度低下率ＧＤＯＰは、

で表される。
さらに、幾何学的位置精度低下率ＰＤＯＰは、
ＰＤＯＰ＝√｛σｘｘ^２＋σｙｙ^２＋σｚｚ^２｝
であらわされる。
このようにして、測位に用いる衛星の配置から、所定の向きに対する測位精度指数を求まる。
【００５３】
【発明の効果】
この発明によれば、２つの測位用衛星からの信号しか受信できない場合でも、通常は測位点の変位検出が可能となる。そのため、４つ以上の測位用衛星が必要な従来の場合に比べて変位検出の稼動率が大幅に改善できる。
【００５４】
また、この発明によれば、受信可能な測位用衛星の数が測位に必要な数より多い場合に、評価対象とする測位用衛星の測位精度に与える影響度を、それ以外の測位用衛星を用いて評価することにより、最適な測位用衛星を用いて高精度な測位および微小な変位を的確に検出できるようになる。
【００５５】
また、この発明によれば、測位に用いた測位用衛星の測位点に対する配置によって定まる測位精度指数に応じて、評価対象とする測位用衛星の測位精度に与える影響度を評価することにより、評価対象以外の測位に用いる測位用衛星の如何なる配置によっても等価的な評価が行えるようになる。
【図面の簡単な説明】
【図１】第１の実施形態に係る変位検出装置を適用した測位システムの構成を示すブロック図
【図２】ＧＰＳ受信機の構成を示すブロック図
【図３】ＧＰＳ受信機の処理内容を示すフローチャート
【図４】センタ側のデータ回収処理装置の行う処理内容を示すフローチャート
【図５】２つの衛星を用いて測位点のずれの有無を検出する処理内容を示すフローチャート
【図６】ドップラーシフト周波数の二重差の例を示す図
【図７】第２の実施形態に係る変位検出装置での、２つの衛星を用いてキャリア位相の二重差により測位点の位置ずれを検出する処理内容を示すフローチャート
【図８】第３の実施形態に係る変位検出装置での変位量検出の処理手順を示すフローチャート
【図９】同変位量検出の説明に供する計算二重差による位置面から観測二重差による位置面への変位の例を示す図
【図１０】第４の実施形態に係る変位検出装置における測位処理の手順を示すフローチャート
【図１１】衛星の評価値を求める手順を示すフローチャート
【図１２】各衛星の配置によって変化する、評価対象の衛星に対する精度指数の例を示す図
【符号の説明】
２−ＧＰＳアンテナ
４−送受信アンテナ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a displacement detection device that receives a signal from a positioning satellite and detects a displacement of a positioning point.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a displacement detection device using GPS positioning has been used to monitor some kind of displacement, such as monitoring a landslide on a slope or a deformation of a dam (for example, see Patent Document 1).
[0003]
Such a device that receives a signal from a GPS satellite and monitors the displacement of a positioning point performs positioning of the positioning point at regular time intervals or at a predetermined timing, and measures the tendency of the timed displacement of the positioning point and It is configured to monitor sudden displacement.
[0004]
[Patent Document 1]
JP-A-6-160509
[Problems to be solved by the invention]
In the GPS positioning, a relative position between a reference GPS antenna and a GPS antenna provided at a positioning point is obtained. In order to perform the positioning, it is necessary to receive signals from at least four GPS satellites. There is. However, in an application field in which displacement detection is performed by GPS positioning, the view of the sky is not always open. For example, in an environment where a landslide on a slope is monitored, a part of the sky is always obstructed by the topography of the slope, so that there is a high probability that a time zone in which signals from four or more GPS satellites cannot be received occurs. Particularly on the northern slope, the number of receivable satellites is originally small due to the relationship between the orbits of GPS satellites, and there is a tendency that a time zone during which positioning cannot be performed tends to occur. Under such a condition that a time zone in which displacement cannot be detected occurs, continuous monitoring cannot be completely performed. In addition, when completely continuous monitoring is required, its application range is limited.
[0006]
On the other hand, in GPS positioning, multipath is a cause of deterioration in positioning accuracy. That is, the direct wave directly incident on the GPS antenna from the GPS satellite and the reflected wave reflected and incident on some radio wave reflector are superimposed, the observation carrier phase fluctuates, and an error occurs in the positioning result. Generally, in order to eliminate multipath, the antenna structure is devised by providing a member that blocks incidence from the direction where reflected waves are likely to arrive, but the disadvantage is that the size of the device increases. was there. Further, since the tracking of the carrier phase is performed in cooperation with the tracking of the C / A code phase, the accuracy of the observed carrier phase is affected by the accuracy of the C / A code phase. Therefore, the correlation is obtained in a narrow time width to reduce the error of the C / A code phase due to the multipath, and the positioning error due to the multipath is reduced by narrowing the bandwidth of the loop filter for tracking the carrier phase. can do. However, when such a correlation process is performed, the overall power consumption increases, which is problematic when, for example, a solar cell is used as a power supply.
[0007]
Since the above-described displacement monitoring usually performs positioning at a stationary point, the state of the error due to multipath is determined by the movement of the GPS satellite and the arrangement of the radio wave reflector around the positioning point. The angular velocity of the GPS satellite is about 0.5 degrees per minute, its movement is very slow when viewed from the positioning point, and the radio wave reflector does not move. The change is very slow. When observed in some actual environments, the double difference in carrier phase fluctuates about ± 0.05 lanes (± 1 cm) in a short cycle due to random noise, and about 1 to 10 minutes due to multipath. It fluctuates over a long period. Therefore, random noise in a short period can be removed by performing averaging with a relatively short time constant, but fluctuation due to multipath can be removed unless averaging is performed for a long time of about 1 to 10 minutes or more. Absent. Therefore, instead of performing such long-time averaging, monitoring is performed while including fluctuations in long-term positioning errors due to multipath, or long-time averaging is performed, and short-term displacement of the positioning point is performed. Monitoring will be ignored.
[0008]
The former problem that displacement cannot be detected when the number of satellites is less than the required number of satellites, and the latter problem of increased positioning error and reduced responsiveness due to multipath, both use the signals from positioning satellites well. To do something. In addition, these problems are not limited to detecting displacements of positioning points for stationary objects such as sloping lands and dams, but are generally encountered when monitoring relative displacements of a plurality of observation points. .
[0009]
Therefore, an object of the present invention is to always perform optimal displacement detection even if the number of receivable satellites varies.
[0010]
Another object of the present invention is to enable detection of displacement of a positioning point even when the number of positioning satellites required for positioning is small, and to be able to receive signals from positioning satellites in excess of the number required for positioning. It is an object of the present invention to provide a displacement detection device that can obtain higher positioning accuracy in a state.
[0011]
[Means for Solving the Problems]
The present invention relates to a displacement detection apparatus for receiving signals transmitted from a plurality of positioning satellites at a plurality of positioning points and detecting a displacement of the positioning points, wherein a Doppler signal of a signal transmitted from at least two positioning satellites is provided. The shift frequency or the amount of carrier phase change per unit time is observed at each positioning point, and a Doppler shift frequency based on observation at the reference point and other positioning points with reference to a predetermined positioning point among a plurality of positioning points. Or means for calculating the Doppler shift frequency or the observed double difference of the carrier phase change per unit time from the carrier phase change per unit time, the position of a reference point and a positioning point, the orbit of the at least two positioning satellites Means for calculating a calculated double difference of the Doppler shift frequency or the carrier phase change per unit time based on the information and the time; The deviation of the observed double difference, is characterized by comprising a means for detecting the relative displacement of the positioning points relative to the reference point.
[0012]
With this configuration, even when only signals from two positioning satellites can be received, displacement detection of a positioning point can be performed. However, the displacement detection accuracy is reduced depending on the arrangement of the two positioning satellites with respect to the positioning point. In some cases, a displacement direction in which a displacement cannot be detected occurs, but the probability that the displacement cannot be detected is low, and the operation rate is greatly improved as compared with the conventional case in which four or more positioning satellites are required. .
[0013]
Further, the present invention observes a carrier phase of a signal transmitted from at least two positioning satellites at each positioning point, and uses a predetermined positioning point among a plurality of positioning points as a reference, and the reference point and another positioning point. Means for determining the observed double difference of the carrier phase from the carrier phase obtained by observation at a point; the position of the reference point and the positioning point; and the calculated double difference of the carrier phase based on the orbit information and time of the two positioning satellites. It is characterized by comprising a means for obtaining, and a means for detecting a relative displacement of a positioning point with respect to a reference point based on a difference between the calculated double difference and the observed double difference.
[0014]
In this way, by detecting the displacement of the positioning point based on the difference between the observed double difference and the calculated double difference of the carrier phase, if the signals from the two positioning satellites can be received, the displacement of the positioning point can be detected. The rate is greatly improved.
[0015]
Further, the present invention estimates the position of the positioning point after the displacement from the line before the displacement of the positioning point in the direction going down the inclined line passing through the positioning point and the equal phase difference plane due to the observation double difference. It is characterized by having means for performing. Thus, not only the presence / absence of displacement of the positioning point but also the displacement amount can be obtained.
[0016]
Also, the present invention provides a means for receiving signals from a plurality of positioning satellites, obtaining an observation carrier phase difference which is a pair of a reference positioning satellite and each of the other positioning satellites, Based on the position of the positioning point measured by using the positioning satellite, and the orbit information and time of the positioning satellite to be the reference and the positioning satellite to be evaluated, the positioning of the reference positioning satellite and the positioning of the evaluation target are performed. Means for calculating a calculated carrier phase difference with a set of satellites, and for the positioning satellite to be evaluated, determining a shift between the observed carrier phase difference and the calculated carrier phase difference, based on the shift of the phase difference. Means for evaluating the positioning accuracy and performing positioning of a positioning point based on the observation distance of the positioning satellite having a high evaluation.
[0017]
In this way, when the number of receivable positioning satellites is larger than the number required for positioning, the degree of influence on the positioning accuracy of the positioning satellite to be evaluated is evaluated using other positioning satellites. . As a result, highly accurate positioning and minute displacement can be accurately detected by using an optimal positioning satellite.
[0018]
Further, in the present invention, the evaluation is corrected according to a positioning accuracy index determined by an arrangement of the positioning satellite used for positioning with respect to a positioning point. As a result, the positioning accuracy can be equally evaluated regardless of the arrangement of the positioning satellites used for positioning other than the evaluation target.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
A configuration of a displacement detection device according to an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a block diagram showing the configuration of an entire system for monitoring a landslide on a slope, for example. In FIG. 1, 2a is a GPS antenna, and 1a is a GPS receiver. The GPS receiver 1a receives signals from a plurality of GPS satellites at the position of the GPS antenna 2a. 3a is a wireless device provided on the positioning point side, and 4a is its transmitting / receiving antenna. These 1a, 2a, 3a and 4a constitute a set of observation devices. 1b to 4b similarly constitute another observation device. The same applies to 1 m to 4 m. Such a plurality of observation devices are installed at predetermined positions on a slope.
[0020]
Reference numeral 6 denotes a wireless device on the center side, and reference numeral 5 denotes a transmitting and receiving antenna. The wireless device 6 on the center side performs data communication with a plurality of wireless devices 3a, 3b,... 3m on the observation device side. 8 is a GPS receiver, 7 is a GPS antenna. The GPS receiver 8 is provided mainly for obtaining a time synchronization signal when performing data communication with a plurality of radios on the observation device side on a predetermined time schedule synchronized with the GPS time (time used in the GPS positioning system). ing. Reference numeral 9 denotes a data recovery processing device which collects observation data of the carrier phase and the Doppler shift frequency for each positioning satellite and each time, which are observed by a plurality of observation devices, and measures displacement of a positioning point of each observation device. To detect. Further, the detection result is transmitted to the outside as necessary.
[0021]
FIG. 2 shows the configuration of one GPS receiver among the plurality of observation devices shown in FIG.
Here, reference numeral 12 denotes a down-converter for converting the frequency of a signal received by the GPS antenna 1 into an intermediate frequency signal, sampling the signal at a predetermined period, and sequentially converting the signal into a digital data string. The reception signal processing unit 13 includes a C / A code correlator and a carrier signal correlator for each of a plurality of channels. The CPU 14 observes the carrier phase of the signal received from each GPS satellite and outputs the signal to the wireless device via the communication interface 17. A program to be executed by the CPU 14 is written in the ROM 15 in advance. The RAM 16 is used as a working area during arithmetic processing.
[0022]
FIG. 3 is a flowchart showing the processing contents of the GPS receiver on the observation device side. When the processing flow is roughly divided, first, a search for a received signal from each GPS satellite is performed, and the C / A code and carrier phase of the received signal are captured and tracked (s1). Then, the observation carrier phase of the received signal from each GPS satellite is obtained (s2). The data of the observed carrier phase is transmitted to the radio as a set of data together with the time data and the satellite number (s3). The wireless device wirelessly transmits these data to the center-side wireless device. By repeating the above processing by each GPS receiver, the data recovery processing device 9 on the center side collects observation carrier phase data for each time and each satellite of each observation device.
[0023]
FIG. 4 is a flowchart showing the processing contents in the data collection processing device 9 on the center side. As shown in FIG. 4, first, if the number of satellites received by the GPS receiver of the observation device to be processed is equal to or greater than the number of satellites capable of three-dimensional positioning due to the carrier phase double difference (four), Positioning of the positioning point is performed based on the carrier phase obtained by observation obtained by receiving signals from those satellites (n1 → n2). Specifically, a double difference of a carrier phase with respect to a GPS antenna of a predetermined observation device out of a plurality of observation devices is obtained, an integer bias thereof is determined by a known integer bias determination method, and a relative position with respect to the reference point is determined. Perform positioning. Then, a deviation amount of the position of the positioning point obtained this time from the position obtained last time or before is detected (n3).
[0024]
When the number of received satellites is less than the number of satellites that can be three-dimensionally positioned (four) due to the normal carrier phase double difference, the presence or absence of a displacement of the positioning point is detected by the method described below ( n4).
The above processing is performed for the positioning points of all the observation devices, and the results are output (n5). In the process of outputting the result, when the displacement amount of the positioning point exceeds a predetermined threshold value, it is considered that the positioning point is displaced, and an alarm is output.
[0025]
FIG. 5 is a flowchart showing the processing content of step n4 shown in FIG. First, a double difference (observed double difference) between the Doppler shift frequencies of two observed satellites is obtained (n11). Subsequently, a double difference in calculation of the Doppler shift frequency is calculated for the two satellites (n12). That is, the moving speeds of the two satellites are obtained from the approximate position of the positioning point, the orbital information of the two satellites at that time and the time, and the Doppler shift frequency is calculated by the geometrical arrangement of the two satellites with respect to the positioning point. Find the difference.
[0026]
Here, the calculated double difference of the Doppler shift frequency will be described with reference to FIG.
If there are two satellites a and b, the reference point is f, the positioning point is m, and the satellite a moves from a1 to a2 and the satellite b moves from b1 to b2 in unit time, the positioning point m the Doppler shift frequency d _m ^a satellite a as seen from the expressed in the following manner.
[0027]
_{^{_{^{_{d m a = l m a2 -l}}}}} m a1
Also, the Doppler shift frequency d _m ^b satellites b as seen from the positioning point m is expressed as follows.
[0028]
_{^{_{^{_{d m b = l m b2 -l}}}}} m b1
Furthermore, the satellite a viewed from the reference point f, each of the Doppler shift frequency of b _d ^f _a, is _d ^{f b} expressed as follows.
[0029]
_{^{_{^{_{d f a = l f a2 -l}}}}} f a1
_{^{_{^{_{d f b = l f b2 -l}}}}} f b1
Here, 1 (ell) is the distance between the satellite and the receiving point, and the subscript is a symbol that identifies the receiving point, and the superscript is the symbol that identifies the satellite.
[0030]
Further, the single difference ∇dm between the satellites of the Doppler shift frequency obtained at the positioning point _m is:
_{_{^{_{^{∇d m = d m a -d m}}}}} b
Is required.
[0031]
Similarly, the single difference 衛星 df between the satellites of the Doppler shift frequency obtained at the reference point _f is
_{_{^{_{^{∇d f = d f a -d f}}}}} b
Is required.
[0032]
Therefore, the double difference Δ∇d of the Doppler shift frequency is
Δ∇d = ∇d _m -∇d _f
Is required.
The calculated double difference of the Doppler shift frequency is obtained as described above.
[0033]
Now, returning to FIG. 5, thereafter, the difference between the observed double difference and the calculated double difference is obtained, and it is determined whether or not there is a significant difference between the double differences (n13). If the value is equal to or larger than a predetermined threshold value ε, it is regarded that the position shift of the positioning point has occurred (n14), and if it is less than ε, it is considered that there is no position shift of the positioning point (n15).
[0034]
Note that “the carrier phase change amount per unit time” may be used instead of the above “Doppler shift frequency”.
[0035]
Next, the configuration of a displacement detection device according to a second embodiment will be described with reference to FIG.
The difference from the displacement detection apparatus shown in the first embodiment is that the processing when the number of received satellites is less than four in which three-dimensional positioning is possible due to the carrier phase double difference (corresponding to step n4 in FIG. 4) Is performed by calculating the double difference of the carrier phase. First, as shown in FIG. 7, a double difference in carrier phase (observed double difference) for two observed satellites is obtained (n21). Subsequently, a double difference in the calculation of the carrier phase is obtained for the two satellites (n22). That is, the positions of the two satellites are obtained from the approximate position of the positioning point, the orbit information of the two satellites at that time and the time, and the double difference of the carrier phase is calculated by the geometrical arrangement of the two satellites with respect to the positioning point. Ask. Thereafter, the difference between the observed double difference and the calculated double difference is obtained as a shift amount (n23). Then, it is determined whether this deviation amount is a significant value (n24). If the value is equal to or larger than a predetermined threshold value ε, it is regarded that the position shift of the positioning point has occurred (n25), and if it is less than ε, it is considered that there is no position shift of the positioning point (n26).
[0036]
In the first and second embodiments, if signals from three satellites are received, the difference between the double differences is calculated in the same manner for another pair of two satellites. Then, if any one of the differences between the two sets of double differences has a significant difference, it is regarded as “there is a shift”.
[0037]
Next, a displacement detection device according to a third embodiment will be described with reference to FIGS.
In the first and second embodiments, only the presence / absence of displacement of the positioning point is detected. However, depending on the environment of the installation location of the observation device, the number of receivable satellites is determined by the difference between the carrier phase and the observation double difference. Even if the number of satellites for which three-dimensional positioning is not possible is less than the number of satellites, the amount of displacement can be estimated. For example, FIG. 9B shows a perspective view of the situation around the installation position of the positioning point m. When an observation device is provided on such a slope, the direction in which the positioning point is displaced by landslides or the like is as follows. Usually in the direction along the slope line. m shows an example of the position before the displacement, and m 'shows an example of the position after the displacement.
[0038]
FIG. 9A shows an example of the calculated double difference and the observed double difference of the carrier phase obtained by using two satellites. The position m of the positioning point before the displacement exists at a predetermined position on an equal phase difference surface (hereinafter, referred to as “position surface”) forming a hyperboloid due to a double difference in carrier phase. Before the displacement, the position plane forming the hyperboloid due to the calculated double difference should match the position plane due to the observed double difference. If the positioning point is displaced from m to m 'due to a landslide or the like, this m' is present somewhere on the position plane due to the observed double difference after the displacement. That is, if only two satellites are used, it is only known that m 'is located at any position on the position plane due to the observed double difference, but the three-dimensional position cannot be obtained.
[0039]
However, as shown in FIG. 9B, since the displacement of the positioning point usually occurs along the slope line, the displacement of the positioning point extends from the position m obtained by observation and calculation before the displacement down the slope line. The intersection between the straight line and the position plane based on the observed double difference can be estimated as the position m 'after the displacement. The distance between m and m 'is the amount of displacement. In this way, the displacement can be obtained even if the number of receivable satellites is two. Note that the line extending in the direction down the inclined line may not be a straight line, but may be a curve according to the terrain.
[0040]
FIG. 8 is a flowchart showing the above processing contents. First, an observed double difference is obtained from the carrier phases observed for the two satellites (n31). Further, the calculated double difference of the carrier phase is obtained for the two satellites (n32). Then, the displacement amount is obtained from the two position planes of the observed double difference and the calculated double difference, and the information on the inclination line direction, and the displacement is output (n33 → n34). If the observed double difference matches the calculated double difference, the displacement amount is of course zero.
Note that the information on the inclined line at the position where each observation device is installed is obtained by calculation based on the topographic map data and the position of the observation device, or is input in advance for each observation device.
[0041]
Next, the configuration of a displacement detection device according to a fourth embodiment will be described with reference to FIGS.
The fourth embodiment is characterized by processing when signals are received from a number of satellites exceeding the number of satellites required for three-dimensional positioning based on the carrier phase double difference. FIG. 10 is a flowchart showing the contents of the processing performed by the data collection processing device 9 shown in FIG. 1 for positioning for each observation device. However, here, the processing for one observation device is shown.
[0042]
First, if the number of received satellites exceeds the number required for three-dimensional positioning (four) due to the double difference in carrier phase, an evaluation value of the degree of influence on the positioning accuracy is determined for each of those satellites. (N41 → n42). After that, four satellites for obtaining the highest positioning accuracy are determined according to the evaluation value, three sets of carrier phase double differences are determined based on the four satellites, and relative positioning with respect to the reference point is performed (n43 → n44).
[0043]
If the number of received satellites is four, positioning is performed using the four satellites, and if less than four, displacement detection is performed by the method described in the first to third embodiments (n45). .
[0044]
FIG. 11 is a flowchart showing the processing procedure of step n42 in FIG. First, a satellite having the highest elevation angle (near the zenith) among the five or more satellites is set as a reference satellite, and a double difference in observation carrier phase is set for a pair of the satellite to be evaluated and the reference satellite (n51 → n52). . Then, a double difference of the calculated carrier phase is obtained from the position of the positioning point obtained by a satellite other than the evaluation target, the position of the reference satellite at that time, and the position of the evaluation target satellite (n53). Subsequently, a positioning accuracy index based on the satellite arrangement described later is obtained (n54). Then, an evaluation value is determined from the difference between the double difference in the observed carrier phase and the double difference in the calculated carrier phase, and the positioning accuracy index (n55). For example, the smaller the difference between the double differences, the higher the evaluation value, and the smaller the positioning accuracy index (the higher the positioning accuracy), the smaller the fluctuation range of the evaluation value based on the difference between the double differences. Accordingly, the evaluation value increases as the positioning accuracy index is larger and the difference between the double differences is smaller. Similarly, the evaluation value is lower as the positioning accuracy index is larger and the difference between the double differences is larger.
[0045]
Next, the positioning accuracy index based on the satellite arrangement will be described with reference to FIG. In FIG. 12, (Sa-Sr) is a line (position line) generated by the intersection between the horizontal plane and the position plane of the carrier phase generated by the pair of two satellites Sa and Sr. (Sb-Sr) is a line (position line) generated by the intersection of the horizontal plane and the position plane of the carrier phase generated by the pair of the two satellites Sb and Sr. Here, a thick line is a position line, and a thin line is a position line adjacent thereto and separated by one wavelength. As described above, a rhombus portion is generated by the intersection of two sets of position lines. When a circumscribed ellipse is drawn on the rhombus, the accuracy index in the short axis direction is the best, and the positioning accuracy in the long axis direction is the worst. Assuming that the precision index is a coefficient when the distance between the position lines (about 2 cm 2) is 1, the precision index in the short axis direction is 1.1 and the precision index in the long axis direction is about 3.3 in this example. .
[0046]
Here, as shown in FIG. 12B, the ellipse is superimposed on a position line generated by the reference satellite Sr and the satellite Se to be evaluated. The diameter extending from the center of the ellipse in the interval direction of the position line represents the accuracy index for the position line. In this example, it is about 2.5. This accuracy index can be quantitatively obtained by the following relational expression.
[0047]
Here, the distance from the i-th satellite to the positioning point is ri.
The coordinates of the positioning point are (xo, yo, zo),
Let the position of the i-th satellite be (xi, yi, zi),
The cosine of the x, y, z directions to each satellite viewed from the positioning point is
αi = (xi−xo) / ri
βi = (yi-yo) / ri
γi = (zi-zo) / ri
Toki,
[0048]
(Equation 1)

[0049]
Then, the weight coefficient matrix is expressed as a covariance matrix
(Equation 2)

[0051]
Is represented by
[0052]
Then, the geometric accuracy reduction rate GDOP due to the satellite arrangement is

Is represented by
Furthermore, the geometrical position accuracy reduction rate PDOP is
^{PDOP = √ {σxx 2 + σyy} 2 + σzz 2}
It is represented by
In this way, a positioning accuracy index for a predetermined direction is obtained from the arrangement of satellites used for positioning.
[0053]
【The invention's effect】
According to the present invention, even when only signals from two positioning satellites can be received, displacement detection of a positioning point can be normally performed. Therefore, the operation rate of displacement detection can be significantly improved as compared with the conventional case that requires four or more positioning satellites.
[0054]
According to the present invention, when the number of receivable positioning satellites is larger than the number required for positioning, the degree of influence on the positioning accuracy of the positioning satellite to be evaluated is determined by using other positioning satellites. By using and evaluating, it is possible to accurately detect high-precision positioning and minute displacement using an optimal positioning satellite.
[0055]
According to the present invention, the degree of influence on the positioning accuracy of the positioning satellite to be evaluated is evaluated in accordance with the positioning accuracy index determined by the positioning of the positioning satellite used for positioning with respect to the positioning point, whereby the evaluation is performed. Equivalent evaluation can be performed by any arrangement of positioning satellites used for positioning other than the target.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a positioning system to which a displacement detection device according to a first embodiment is applied. FIG. 2 is a block diagram showing a configuration of a GPS receiver. FIG. 3 shows processing contents of the GPS receiver. Flowchart [FIG. 4] Flowchart showing processing performed by the data collection processing device on the center side [FIG. 5] Flowchart showing processing performed to detect the presence / absence of a displacement of a positioning point using two satellites [FIG. 6] Doppler shift frequency FIG. 7 is a diagram showing an example of the double difference of FIG. 7 in the displacement detection device according to the second embodiment of the process of detecting the displacement of the positioning point by the double difference of the carrier phase using two satellites. FIG. 8 is a flowchart showing a processing procedure for detecting the amount of displacement in the displacement detecting device according to the third embodiment. FIG. 10 is a diagram illustrating an example of displacement to a position plane due to a double measurement difference. FIG. 10 is a flowchart illustrating a procedure of a positioning process in a displacement detection device according to a fourth embodiment. FIG. 11 is a diagram illustrating a procedure for obtaining an evaluation value of a satellite. Flowchart [FIG. 12] A diagram showing an example of an accuracy index for a satellite to be evaluated, which varies depending on the arrangement of each satellite.
2-GPS antenna 4-transmission / reception antenna

Claims

In a plurality of positioning points, in a displacement detection device that receives a signal transmitted from a plurality of positioning satellites and detects a displacement of the positioning point,
A Doppler shift frequency or a carrier phase change per unit time of signals transmitted from at least two positioning satellites is observed at each positioning point, and a predetermined positioning point among a plurality of positioning points is used as a reference, and the reference point is used as a reference point. And means for obtaining an observed double difference of the Doppler shift frequency or the carrier phase change amount per unit time from the Doppler shift frequency or the carrier phase change amount per unit time by observation at another positioning point,
Means for obtaining a calculated double difference of the Doppler shift frequency or the carrier phase change per unit time based on the positions of the reference point and the positioning point, the orbit information and the time of the at least two positioning satellites,
Means for detecting a relative displacement of a positioning point with respect to a reference point based on a difference between the calculated double difference and the observed double difference.

In a plurality of positioning points, in a displacement detection device that receives a signal transmitted from a plurality of positioning satellites and detects a displacement of the positioning point,
A carrier phase of a signal transmitted from at least two positioning satellites is observed at each positioning point, and a predetermined positioning point among a plurality of positioning points is used as a reference, and a carrier obtained by observation at the reference point and another positioning point is used. Means for obtaining the observed double difference of the carrier phase from the phase;
Means for calculating a calculated double difference of the carrier phase based on the positions of the reference point and the positioning point, the orbit information and the time of the two positioning satellites,
Means for detecting a relative displacement of a positioning point with respect to a reference point based on a difference between the calculated double difference and the observed double difference.

Means for estimating the position of the positioning point after displacement from a line extending in a direction going down a slope passing through the positioning point from the position before displacement of the positioning point and an equal phase difference surface due to the observation double difference. Item 3. The displacement detection device according to Item 2.

In a plurality of positioning points, in a displacement detection device that receives a signal transmitted from a plurality of positioning satellites and detects a displacement of the positioning point,
Means for receiving signals from a plurality of positioning satellites, and obtaining an observation carrier phase difference that pairs a positioning satellite as a reference and each of the other positioning satellites,
Based on the position of the positioning point measured by using the positioning satellites not to be evaluated and the orbit information and time of the positioning satellite to be evaluated and the positioning satellite to be evaluated, Means for calculating a calculated carrier phase difference with the positioning satellite to be evaluated,
For the positioning satellite to be evaluated, the difference between the observed carrier phase difference and the calculated carrier phase difference is determined, and based on the difference in phase difference, an evaluation relating to positioning accuracy is performed. Means for performing positioning of a positioning point based on the observation distance.

The displacement detection device according to claim 4, wherein the evaluation is corrected in accordance with a positioning accuracy index determined by an arrangement of the positioning satellite used for positioning with respect to a positioning point.