Worksheet

GPS: From Signals to a Position

Analyze how an original article about GPS uses explanations, examples, contrasts, and qualifications to develop ideas within paragraphs.

Grade 8ELAInteractive · Printable

Aligned toRI.8.5

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1 Common Core standard
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13 questions
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Details

Format: Interactive · Printable
Grade: Grade 8
Subject: ELA
Question types: Multiple choice, Circle the answer, Short answer

About this worksheet

What students practice

Students analyze how individual sentences develop and refine a paragraph’s key idea.
Students explain how examples, contrasts, and qualifications shape an informational paragraph.

How to use

Have students read and annotate the article before answering. Ask them to describe each sentence’s job, then use the final response to explain a paragraph’s structure.

Curriculum

Common Core standard covered

RI.8.5

Analyze the structure of a paragraph in detail, including how particular sentences develop and refine a key idea.

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Name Date

GPS: From Signals to a Position

Analyze how sentences build, explain, and qualify an idea.

Read and trace the explanation

Read the article. For each question, focus on how the sentences work together, not just the facts they contain.

A Position Built from Timing

1A location dot on a phone’s map looks simple, but producing it requires information arriving from far above Earth. GPS, the Global Positioning System, uses a network of orbiting satellites that broadcast radio signals. Those signals include information about when they were sent and where the satellites were in their orbits. A receiver, such as the one in a phone, uses these messages to calculate its own position. The satellites do not need a message from that receiver to make this calculation possible.

2A receiver begins by estimating how long a satellite’s signal took to reach it. Because radio signals travel at the speed of light, travel time can be converted into an estimate of distance. One distance alone places the receiver somewhere on an imaginary sphere centered on that satellite, rather than at a single known point. Comparing several such distance measurements narrows the possibilities to a common position. This explanation leaves out an important difficulty, however: the receiver’s clock is not perfectly synchronized with the satellites’ clocks.

3Even a tiny clock error can produce a large error in the distance calculation because radio signals move so quickly. Imagine timing a runner with a stopwatch that starts late: the recorded time would not match the actual travel time. The consequences are much greater for a radio signal, so a GPS receiver generally uses measurements from at least four satellites to solve for its position and its clock error together. The additional measurement therefore helps correct the timing problem rather than simply providing another vote for a location.

4Having enough satellite measurements does not guarantee that every measurement is equally useful. A building can block a signal, while another surface can reflect a signal toward the receiver along a longer path. That reflected signal arrives later than a direct signal would, which can make the satellite seem farther away. Receivers can compare available measurements and reject some suspicious ones, but these methods cannot remove every source of error.

5Calculating a position is also different from displaying useful directions. GPS supplies location information; mapping software combines that information with stored road layouts and route instructions. A device may receive satellite signals without an internet connection, although downloading a new map or current traffic information can require a separate connection. Thus, a working location dot and a complete navigation service depend on related but distinct kinds of information.

In paragraph 2, how does the sentence beginning “Comparing several” develop the explanation that comes before it?

A. It explains how combining measurements reduces the possible locations.
B. It contrasts radio signals with another method of measuring travel time.
C. It gives a reason that one satellite can identify an exact position.
D. It illustrates how receivers send their measurements back to satellites.

Underline the sentence from paragraph 2 that explains how the receiver turns a signal’s travel time into a distance.

A receiver begins by estimating how long a satellite’s signal took to reach it.Because radio signals travel at the speed of light, travel time can be converted into an estimate of distance.Comparing several such distance measurements narrows the possibilities to a common position.This explanation leaves out an important difficulty, however: the receiver’s clock is not perfectly synchronized with the satellites’ clocks.

How do the second and third sentences of paragraph 1 work together?

A. The second presents a problem, and the third evaluates two possible solutions.
B. The second introduces an example, and the third compares it with another system.
C. The second introduces satellite signals, and the third specifies their contents.
D. The second describes an effect, and the third disputes the suggested cause.

What does the final sentence of paragraph 1 add to the description of the receiver’s role?

A. It clarifies that calculating a position does not require a return message.
B. It limits position calculations to receivers installed inside mobile phones.
C. It identifies the information that receivers broadcast to orbiting satellites.
D. It explains why a phone must download a map before receiving signals.

Examine sentence relationships

Return to the named paragraph before choosing an answer. Notice causes, examples, limitations, and transitions.

Why does paragraph 2 end with the sentence about the receiver’s clock?

A. It summarizes the timing solution that the paragraph has already explained.
B. It qualifies the simplified explanation and introduces the next paragraph’s problem.
C. It rejects distance measurement and introduces an unrelated positioning method.
D. It changes the subject from satellite signals to the design of phone screens.

In paragraph 3, what is the function of the example about timing a runner?

A. It presents a competing explanation for errors caused by reflected signals.
B. It provides evidence that sports stopwatches use signals from GPS satellites.
C. It makes the effect of incorrect timing easier to understand through comparison.
D. It explains why a runner’s location is harder to calculate than a phone’s.

In paragraph 3, why does the author follow the runner example with “The consequences are much greater for a radio signal”?

A. To suggest that the runner example contradicts the paragraph’s opening.
B. To show that runners and radio signals produce errors of similar size.
C. To replace the timing problem with a problem involving blocked signals.
D. To show where the familiar comparison needs to be adjusted for GPS.

How does the final sentence of paragraph 3 refine the explanation of the additional satellite measurement?

A. It distinguishes correcting clock error from merely adding another location estimate.
B. It suggests that the receiver counts identical location reports from satellites.
C. It shifts the explanation from correcting time to measuring a runner’s speed.
D. It adds a second example of a receiver getting information from a map.

A student says the opening sentence of paragraph 4 repeats the point that more measurements improve a calculation. Which analysis best corrects the student?

A. The sentence confirms that enough measurements make all position calculations reliable.
B. The sentence shifts attention from the number of measurements to their usefulness.
C. The sentence argues that signal reflection is the main purpose of satellite networks.
D. The sentence explains that receivers use fewer satellites when buildings are nearby.

Evaluate the paragraph design

Analyze why the author includes and orders particular sentences. Support your final explanation with details from the article.

10.

In paragraph 4, what explanatory link would be lost if the sentence beginning “That reflected signal” were removed?

A. The link between an imaginary sphere and a runner’s recorded travel time.
B. The link between a receiver’s return message and a satellite’s orbital position.
C. The link between a longer signal path and an inaccurate distance estimate.
D. The link between blocked signals and the need to download current road maps.

11.

The final sentence of paragraph 4 describes what receivers can do, then adds “but these methods cannot remove every source of error.” What is the effect of that second part?

A. It identifies the clock problem as the only remaining source of measurement error.
B. It limits the solution so readers do not mistake improvement for complete accuracy.
C. It gives an additional example of the information carried inside satellite signals.
D. It suggests that comparing measurements is less useful than ignoring reflected signals.

12.

Which description best traces the sentence-by-sentence structure of paragraph 5?

A. It states a question, lists competing answers, rejects one answer, and proposes a test.
B. It introduces an error, gives its cause, tests a solution, and reports the result.
C. It describes a device, recounts its invention, explains a later change, and predicts its future.
D. It states a distinction, explains the roles, adds a connection example, and draws a conclusion.

13.

Explain how paragraph 4 develops and refines its key idea from beginning to end. Describe the jobs of at least three sentences and explain why their order helps the reader.