题目内容
（请给出正确答案）
A．by inputting the exact address.
B．by indicating the location of his car.
C．by checking his computer database.
D．by giving vocal orders to the computer.
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更多“With a navigation computer, a …”相关的问题
Despite their varied designs, navigation computers used in cars ______.
A．are more or less the same price.
B．provide directions in much the same way.
C．work on more or less the same principles.
D．receive instructions from the same satellites.
A．Enforcing laws controlling navigation, shipping, immigration and fishing.
B．Enforcing laws affecting the privately-owned bests in the U.S.
C．Searching for missing beats and rescuing people.
D．Training people to good swimmers along the beach.
The navigation systems in cars like Lexus, BMW and Audi are mentioned to show ______.
A．the immaturity of the new technology.
B．the superiority of the global positioning system.
C．the cause of price fluctuations in car equipment.
D．the different ways of providing guidance to the driver.
In order to predict distortions, scientists need to______.
A．improve the severity of radio, radar and navigation signals
B．improve the accuracy of the satellite-based systems
C．study the charged particles in the ionosphere
D．study the thick regions in the ionosphere
A.作用为多传感器融合，进行更准确的位姿估计
B.可选的传感器数据为IMU、Visual Odometry、Wheel Odometry
C.默认发布robot_pose_ekf/odom_combined消息
D.默认发布odom → base_footprint的tf
A. emergency lighting for occupied areas,navigation lights
B. the driving motors of the emergency bilge pump,fire pumps,and steering gear
C. communications systems and alarm systems
D. all of the above
GASS的全称是全球导航卫星系统(Global Navigation Satellite System)，它泛指所有的卫星导航系统，包括全球的，区域的和及其相关增强的，如美国的GPS、俄罗斯的Glonass、欧洲的Galileo、中国的北斗卫星导航系统，相关增强系统，如美国的WAAS(广域增强系统)、欧洲的EGNOS(欧洲静地导航重叠系统)和日本的MSAS(多功能运输卫星增强系统)等。 这段文字介绍的是：
A.GNSS的定义
B.GNSS的构成
C.GNSS的功能
D.GNSS的来源
Understanding the shape and size of the ionosphere is an important first step in figuring out how particularly dense regions within it may distort radio, radar and navigation signals. Such distortions can make communications and satellite-based systems less reliable.
"In order to predict how severe those distortions will be, it's necessary to know how big those structures in the ionosphere are and where they exist," Roderick Hellis, with the Space sciences Center at the University of Texas in Dallas, told Discovery News.
Hellis and his colleagues have been using a suite of NASA instruments called CINDI, which fly on the U.S. Air Force Communication/Navigation Outage Forecast System (C/NOFS) satellite between 250 miles and 530 miles around the planet's equator.
The researchers never expected to encounter the edge of Earth's ionosphere at those altitudes, but that is exactly what happened during the summer of 2008, a time when the solar activity was unusually weak.
"It was a real combination of low solar activity and the satellite's range," Hellis said. "We didn't expect to be able to look at the top of the ionosphere in all places." Computer models based on previous research had predicted the ionosphere to be about 370 miles above Earth at night and about 620 miles up during the day--the variation due to temperature and other factors.
Instead, the CINDI team discovered that the transition between the ionosphere and space was about 250 miles above Earth at night and about 500 miles up during the day.
The ionosphere is primarily caused by extreme ultraviolet energy from the sun.
"It's powerful enough that those photons (光子) can ionize (使……电离) atoms in Earth's upper atmosphere," said David Hathaway, a solar physicist at NASA's Marshall Space Flight Center in Huntsville, Ala. "When you have a geomagnetic disturbance or a solar flare going off, you can get an ionosphere that is uneven, which can cause problems with radio signals and GPS satellite signals, which have to pass through."
The findings were presented at the annual American Geophysical Union conference in San Francisco last month.
CINDI is an acronym for Coupled Ion Neutral Dynamics Investigation. The device works by separately measuring ionized and neutral particles at altitudes where the Air Force satellite flies. A similar device is on another polar-orbiting Air Force spacecraft.
The researchers hope to keep using CINDI as solar activity picks up in the sun's new 11-year cycle. The next solar maximum is expected in late 2011 or 2012.
We have always had a misconception about______.
A．how far away the upper edge of the ionosphere is
B．how many particles comprise the ionosphere
C．how long the ionosphere has been existing
D．how the ionosphere extends into space
