Projections
What is a map projection?
A method for representing Earth's curved surface on a flat map.
Which map shows country and state borders?
Political map.
What is a contour line?
A line connecting points of equal elevation.
What does GIS stand for?
Geographic Information System.
A cartographer wants to make a map of the entire world on a flat sheet of paper. Why can't the cartographer preserve the shape, area, distance, and direction of every location perfectly?
Because Earth is curved and a flat map cannot represent its entire surface without some distortion.
Name the two shapes that can be flattened into a plane for map projections.
A cylinder and a cone.
Which map shows natural features like rivers and mountains?
Geographic/physical map.
What does a benchmark help a surveyor determine?
A known reference elevation.
What does it mean for GIS data to be organized in layers?
Different types of information are stored separately and can be viewed together or compared.
Why is sonar useful for mapping the ocean floor?
Sonar works underwater by using sound echoes to estimate depth and map seafloor features.
What is a gnomonic projection?
A projection made by projecting points from Earth's center onto a plane.
Which map uses contour lines to show elevation?
Topographic map.
What tool uses sound waves to map the ocean floor?
Sonar, which sends sound waves and measures returning echoes.
Name two ways geographic data can be collected.
Examples: roads, population, elevation, land use, or rivers.
What are minutes and seconds used to measure in coordinates?
Angular subdivisions of degrees and minutes used to express precise coordinates.
Why do all flat maps have some distortion?
Earth is curved, so flattening its surface changes some combination of shape, area, distance, or direction.
A map shows population density by color. What type of map is it?
Thematic map.
How can contour lines help you understand the shape of land?
Examples: surveying, GPS, aerial photography, satellite imagery, remote sensing, or sonar.
Give one advantage of GIS.
GIS can combine and analyze information to reveal patterns and support decisions.
Two locations have the same latitude but different longitudes. What does that tell you about their positions on Earth?
They are at the same distance north or south of the Equator, but at different positions east or west.
Why is a gnomonic projection useful for polar regions?
It can represent polar regions, although distortion increases farther from the projection's center.
A map shows roads, elevation, and rivers. How could you identify whether it is topographic, political, or thematic?
Look at the map's purpose and features. Borders suggest political; elevation and contour lines suggest topographic; a particular subject or pattern suggests thematic.
What is the difference between a benchmark and a contour line?
A benchmark is a fixed reference point of known elevation; a contour line connects points of equal elevation.
How could GIS layers help a town choose where to build a new fire station?
A town could overlay roads, population, hydrants, and existing stations to find an accessible location that serves many people.
A location is 40° 15′ 30″ N. Explain what the degrees, minutes, and seconds represent.
Degrees give the main angular measurement, minutes divide each degree into 60 parts, and seconds divide each minute into 60 parts. The N indicates north of the Equator.