# Global Positioning Subject Review

1. The science of measuring and monitoring the size and shape of the Earth is ___________________.
2. By looking at the height, angles and distances between numerous locations on the Earth’s surface, geodesists create a ___________________.
3. The Earth’s surface rises and falls about 30 ___________________. Everyday under the gravitational influences of the moon and the sun.
4. The Earth’s outermost layer is called the _________________.
5. The plates that make up the Earth’s outer layer ride atop a sea of molten rock called ___________________.
6. Plate ___________________. is the scientific discipline that looks at how the Earth’s plates shift and interact, especially in relation to earthquakes and volcanoes.

7. WORD BANK
• Aristotle
• Geographic Information System
• benchmarks
• Global Positioning System
• San Andreas Fault
• datums
• National Spatial Reference System
• longitude
• triangulation
• time
• magma
• tectonics
• masses
• gravity
• higher
• gravimeters
• Thomas Jefferson
• geoid
• unevenly
• latitude
• billionths
• Continuously Operating Reference Stations
• oblate
• ellipsoid
• geodesy
• centimeters
• horizontal
• crust
• vertical
• differential
• subsidence
• refusal

8. The Greek philosopher ___________________ is credited as the first person to try and calculate the size of the Earth by determining its circumference.
9. A method of determining the position of a fixed point from the angles to it from two fixed points a known distance apart. _____________________
10. The Earth is flattened into the shape of an ________________ sphere.
11. To measure the Earth, and avoid the problems that places like the Grand Canyon present, geodesists use a theoretical, like the Grand Canyon present, geodesists use a theoretical, created by rotating an ellipse around its shorter axis.
12. To account for the reality of the Earth’s surface, geodesists use a shape called the ___________________ that refers to mean sea level.
13. The earth’s mass is ___________________ distributed, meaning that certain areas of the planet experience more gravitational “pull” than others.
14. ___________________ are sets of data that are the basis for all geodetic survey work. In the United States, horizontal and vertical datums make up a system called the ___________________.
15. The ___________________ datum is a collection of specific points on the Earth that have been identified according to their precise northerly or southerly location and easterly or westerly location.
16. The northerly or southerly location of a point on the Earth’s surface is known as the point’s __________________.
17. The easterly or westerly location of a point on the Earth’s surface is known as the point’s ___________________.
18. Surveyors markpositions with brass discs or monuments called ___________________.
19. Surveyors now rely almost exclusively on the ____________ to identify locations on the Earth.
20. The ___________________ is where two plates of the Earth’s crust meet, and is responsible for many earthquakes in California.
21. The ___________________ datum is a collection of positions whose heights above or below mean sea level is known.
22. The traditional method for setting vertical benchmarks is called ___________________ leveling subsidence land sinking
23. Gravitational attraction between two bodies is stronger when the ___________________ of the objects are greater and closer together.
24. Because the Earth’s mass and density vary at different locations on the planet, ___________________ also varies.
25. In areas where the Earth’s gravitational forces are weaker, mean sea level will ___________________.
26. ___________________ measure the gravitational pull on a suspended mass.
27. ___________________ established the Survey of the Coast, which later evolved into the National Geodetic Survey.
28. The National Geodetic Survey uses markers made from long steel rods driven to ___________________ (pushed into the ground until they won’t go any farther).
29. GPS receivers calculate the distance to GPS satellites by measuring ___________________.
30. GPS satellites have very precise clocks that tell time within three nanoseconds or three ___________________. (0.000000003) of a second.
31. ___________________ is a network of hundreds of station ary permanently operating GPS receivers throughout the United States that can be used to accurately determine position.
32. In a ___________________, specific information about a place—such as the locations of utility lines, roads, streams, buildings, and even trees and animal populations—is layered over a set of geodetic data.

### Across

2. The Earth is flattened into the shape of an _____ sphere.

8. The plates that make up the Earth’s outer layer ride atop a sea of molten rock called _____.

10. _____ are sets of data that are the basis for all geodetic survey work.

12. In areas where the Earth’s gravitational forces are weaker, mean sea level will _____.

14. Established the Survey of the Coast, which later evolved into the National Geodetic Survey. [2 words]

15. In the United States, horizontal and vertical datums make up a system called the _____. [abbrev]

17. The easterly or westerly location of a point on the Earth’s surface is known as the point’s _____.

22. The Earth’s surface rises and falls about 30 _____ everyday under the gravitational influences of the moon and the sun.

24. The _____ is where two plates of the Earth’s crust meet and is responsible for many earthquakes in California. [3 words]

27. The traditional method for setting vertical benchmarks is called _____ leveling.

29. land sinking

31. The Earth’s outermost layer is called the _____.

32. The northerly or southerly location of a point on the Earth’s surface is known as the point’s _____.

### Down

1. By looking at the height, angles and distances between numerous locations on the Earth’s surface, geodesists create a _____. [3 words]

3. A method of determining the position of a fixed point from the angles to it from two fixed points a known distance apart.

3. __________ results in an overproduction of organic matter, especially algae.

4. Surveyors markpositions with brass discs or monuments called _____.

5. GPS satellites have very precise clocks that tell time within three nanoseconds or three _____ (0.000000003) of a second.

6. The Greek philosopher _____ is credited as the first person to try and calculate the size of the Earth by determining its circumference.

7. Plate _____ is the scientific discipline that looks at how the Earth’s plates shift and interact, especially in relation to earthquakes and volcanoes.

9. The Earth’s mass is _____ distributed, meaning that certain areas of the planet experience more gravitational “pull” than others.

11. The _____ datum is a collection of positions whose heights above or below mean sea level is known.

13. The _____ datum is a collection of specific points on the Earth that have been identified according to their precise northerly or southerly location and easterly or westerly location.

16. To account for the reality of the Earth’s surface, geodesists use a shape called the _____ that refers to mean sea level.

18. Gravitational attraction between two bodies is stronger when the _____ of the objects are greater and closer together.

19. Surveyors now rely almost exclusively on the _____ to identify locations on the Earth. [abbrev]

20. Because the Earth’s mass and density vary at different locations on the planet, _____ also varies.

21. The National Geodetic Survey uses markers made from long steel rods driven to _____ (pushed into the ground until they won’t go any farther).

23. _____ is a network of hundreds of stationary permanently operating GPS receivers throughout the United States that can be used to accurately determine position. [abbrev]

25. In a _____, specific information about a place—such as the locations of utility lines, roads, streams, buildings, and even trees and animal populations—is layered over a set of geodetic data. [abbrev]

26. The science of measuring and monitoring the size and shape of the Earth.

28. _____ measure the gravitational pull on a suspended mass.

30. To measure the Earth, and avoid the problems that places like the Grand Canyon present, geodesists use a theoretical, mathematical surface called the _____ that is created by rotating an ellipse around its shorter axis.

33. GPS receivers calculate the distance to GPS satellites by measuring _____.

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