問99
頻出度★★☆
GPSの電波を捕捉しにくいビルの谷間や狭い路地などでも位置を計測することができるように，特定の地域の上空に比較的長く留まる軌道をとり，GPSと併用することによって，より高い測位精度を実現するものはどれか。
令和6年度 ITパスポート試験 問99
ストラテジ系ビジネスインダストリ › ビジネスシステム
This question's explanation and your answers so far.
解説
問 99
Incorrectア
Assisted GPS (A-GPS) is a technology that uses communication such as a mobile phone network to receive satellite orbit information (assist data) in advance, thereby speeding up the start of positioning (the first fix). It only makes the beginning of positioning faster; it is not a satellite that takes an orbit staying long over a specific region, so it is wrong.
Incorrectイ
A gyroscope sensor is a sensor that detects angular velocity (rotation and changes in orientation), and it is used together with sensors such as an acceleration sensor to autonomously estimate the direction of movement or attitude. It does not measure position using radio waves from satellites and has nothing to do with orbits or positioning accuracy, so it is wrong.
- ウ
正解 The correct answer is ウ, the Quasi-zenith satellite. A quasi-zenith satellite system (called Michibiki in Japan, i.e. QZSS) is a satellite that takes a quasi-zenith orbit, staying relatively long over the sky of a specific region (near Japan), and it can send radio waves from a high elevation angle close to the zenith (straight overhead). For this reason, even in places where low-angle GPS satellites are blocked and radio waves are hard to capture, such as gaps between buildings or narrow alleys, satellites are easy to find; and by being used together with GPS it increases the number of usable satellites, achieving higher positioning accuracy. It meets all of the conditions in the question: an orbit that stays long over the sky of a specific region, being used together with GPS, and improving positioning accuracy.
Incorrectエ
A probe car refers to a mechanism (probe information) that collects data such as the position and speed of cars while they are running, and uses it to grasp traffic conditions and road information. It is a vehicle that gathers data, not a satellite that takes an orbit staying in the sky, so it is wrong.
ここがポイント
- A quasi-zenith satellite (QZSS, Michibiki) takes a quasi-zenith orbit that stays long near the zenith of a specific region, and it complements and reinforces GPS to improve positioning accuracy. Because it has a high elevation angle close to the zenith, a key feature is that it is easy to capture even in places with many obstacles, such as gaps between buildings.
- The point is to distinguish related terms of positioning and location information. Assisted GPS speeds up the first fix, a gyroscope sensor enables autonomous navigation by detecting angular velocity, and a probe car collects traffic data from running vehicles, each playing a different role.
用語