Worksheet

GPS: What the Signals Can Tell Us

Read an original article about GPS and use multiple pieces of evidence to support direct statements and inferences.

Grade 7ELAInteractive · Printable

Aligned toRI.7.1

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1 Common Core standard
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13 questions
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Format: Interactive · Printable
Grade: Grade 7
Subject: ELA
Question types: Multiple choice, Circle the answer, Short answer

About this worksheet

What students practice

Students cite several details that support direct statements about how GPS works.
Students connect evidence across paragraphs to support inferences and identify unsupported conclusions.

How to use

Have students read and annotate the article before answering. For the written response, ask them to explain how each cited detail supports their conclusion.

Curriculum

Common Core standard covered

RI.7.1

Cite several pieces of evidence from an informational text to support what it says directly and what can be inferred.

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GPS: What the Signals Can Tell Us

Use several details to separate supported conclusions from assumptions.

Read the article

Notice which tasks belong to satellites, the GPS receiver, and mapping software.

A Location Built from Time

1A phone displays a dot on a map, but no satellite is watching that dot move. GPS, the Global Positioning System, works through radio signals sent by satellites orbiting Earth. Each signal includes information about the satellite’s position and when the signal was sent. A GPS receiver, such as the one in a phone, listens to those broadcasts. It does not need to send a message back to the satellites to calculate its location.

2The receiver compares a signal’s sending time with its arrival time. Radio signals travel at the speed of light, so travel time can be used to estimate distance. Even a tiny timing error can produce a large distance error. One satellite’s signal cannot identify a unique location: many places could be the same distance from that satellite. Measurements from additional satellites narrow the possibilities.

3The receiver’s clock creates another challenge. Satellite clocks are extremely precise, while a phone’s clock is much less precise. A receiver generally needs signals from at least four satellites to calculate its three-dimensional position and correct its clock error. The receiver combines these measurements rather than choosing the strongest signal as its answer. Receiving more signals can help, although signal quality and the satellites’ arrangement in the sky also matter.

4A clear view of the sky helps signals reach a receiver directly. Beside tall buildings, some signals may be blocked. Others may bounce off walls before reaching the device, taking a longer path. The receiver can interpret that extra travel time as extra distance. These effects help explain why a location dot may drift or jump even when someone is standing still. A receiver indoors may struggle to obtain a usable position at all.

5Finding coordinates is different from drawing a map or planning a route. Mapping software uses coordinates to place a dot on stored map information. It also uses information about streets and paths to suggest directions. A road missing from the map cannot be added merely by receiving better satellite signals. Likewise, a correct location does not guarantee that the software knows about a recent road closure.

6GPS reception itself does not require a cellular data connection. A device with suitable downloaded maps can use GPS while offline. Without downloaded information, an app may be unable to display a detailed map or obtain current traffic reports. Conversely, having a cellular connection does not remove buildings that block satellite signals. Understanding these separate jobs helps a user investigate whether a problem involves reception, map information, or an online service.

Build and Test Conclusions

Use only the article. Choose one answer unless a question asks for two sentences. Return to the numbered paragraphs to check your evidence.

According to paragraphs 1 and 2, how does a receiver estimate its distance from a satellite?

A. It measures how strongly the satellite can detect the phone.
B. It measures the time a reply takes to return to the satellite.
C. It compares its map’s street lengths with the satellite’s orbit.
D. It compares the signal’s travel time with the speed of light.

Which pair of details best supports the answer to question 1?

A. Signals include satellite positions; maps contain information about streets.
B. A receiver compares sending and arrival times; signals travel at the speed of light.
C. Satellites orbit Earth; a phone can contain a GPS receiver.
D. A receiver listens to broadcasts; additional satellites narrow the possibilities.

What can be inferred from paragraph 2 about a perfectly measured distance from just one satellite?

A. It would provide the receiver with a detailed street map.
B. It would remove the need to receive other satellite signals.
C. It would reveal whether nearby roads were open to traffic.
D. It would leave more than one possible location for the receiver.

Underline the ONE sentence from paragraph 2 that most directly supports the inference in question 3.

The receiver compares a signal’s sending time with its arrival time.Radio signals travel at the speed of light, so travel time can be used to estimate distance.Even a tiny timing error can produce a large distance error.One satellite’s signal cannot identify a unique location: many places could be the same distance from that satellite.Measurements from additional satellites narrow the possibilities.

A reader says, “The receiver finds its position by picking whichever satellite signal is strongest.” Which correction is supported by paragraph 3?

A. It sends its clock reading to a satellite for a location.
B. It chooses the nearest satellite and ignores its own clock.
C. It combines measurements and accounts for its clock’s error.
D. It replaces satellite measurements with downloaded street information.

Which pair of details from paragraph 3 best supports the correction in question 5?

A. Four signals generally allow clock correction; the receiver combines measurements.
B. Phone clocks are less precise; receiving more signals can sometimes help.
C. Signal quality matters; satellite clocks are more precise than phone clocks.
D. Satellite clocks are precise; satellites have an arrangement in the sky.

A person remains on the same sidewalk, but the phone’s location dot moves. Which inference is best supported by paragraph 4?

A. The person must have lost access to a cellular data service.
B. Nearby structures may have interfered with the signals’ paths.
C. The phone must have downloaded an outdated map of the sidewalk.
D. The satellites must have stopped including times in their signals.

Underline TWO sentences from paragraph 4 that explain how a reflected signal could lead to the position error in question 7.

A clear view of the sky helps signals reach a receiver directly.Beside tall buildings, some signals may be blocked.Others may bounce off walls before reaching the device, taking a longer path.The receiver can interpret that extra travel time as extra distance.These effects help explain why a location dot may drift or jump even when someone is standing still.A receiver indoors may struggle to obtain a usable position at all.

Underline TWO sentences from paragraph 5 that directly show why accurate GPS reception may not solve a route-information problem.

Finding coordinates is different from drawing a map or planning a route.Mapping software uses coordinates to place a dot on stored map information.It also uses information about streets and paths to suggest directions.A road missing from the map cannot be added merely by receiving better satellite signals.Likewise, a correct location does not guarantee that the software knows about a recent road closure.

10.

A reader cites two details: GPS reception does not require cellular data, and a device with suitable downloaded maps can use GPS offline. Which conclusion do BOTH details support?

A. A device can receive GPS information and use a map without cellular data.
B. Downloading maps improves the paths that radio signals take to a receiver.
C. An offline device can obtain current traffic reports from satellite signals.
D. A cellular connection is needed to calculate distance from satellite signals.

11.

Which pair of details best supports this conclusion: A location problem and a missing-map problem may need different solutions?

A. Satellites orbit Earth; radio signals travel at the speed of light.
B. Receivers listen to broadcasts; signals contain the satellite’s position.
C. Buildings can block signals; an app without downloaded information may lack a detailed map.
D. Satellite clocks are precise; one satellite leaves several possible receiver locations.

12.

A student argues, “If a phone receives more satellite signals, its directions will include every recent road closure.” Which evaluation uses the article’s evidence most accurately?

A. The claim is unsupported because added signals may help positioning, but closure knowledge is separate.
B. The claim is supported because mapping software uses coordinates to place a dot on a map.
C. The claim is supported because more signals can help and receivers combine measurements.
D. The claim is unsupported because receivers estimate distance without using signal travel time.

13.

A phone has cellular service, but its location dot jumps beside tall buildings and its suggested route uses a recently closed road. Explain why cellular service does not guarantee that either problem will disappear. Cite at least three specific details from at least two paragraphs, and connect each detail to your explanation.