Map Projections Used in US Mapping Quiz

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Map Projections Used in US Mapping Quiz

Distortions & uses (10 questions).

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Map Projections Used in US Mapping Quiz: Quick Study Notes

Map projections are mathematical transformations used to represent the curved surface of the Earth on a flat map. In the United States, specific projections are standardized to minimize distortion for surveying, navigation, and statistical analysis.

Albers Equal Area The standard for US Census maps and thematic layouts. It preserves land area, allowing for accurate density comparisons across the country.
Lambert Conformal Used in the State Plane Coordinate System for states that are elongated East-to-West (e.g., Tennessee, Kentucky) to minimize scale error.
Transverse Mercator Used in the State Plane Coordinate System for states elongated North-to-South (e.g., Illinois, Vermont) and the basis of the UTM system.
Web Mercator The standard for online mapping (Google, OpenStreetMap). It preserves angles but heavily distorts area near the poles.

Key Takeaways

  • No projection can preserve area, shape, distance, and direction simultaneously.
  • Conformal projections (Lambert, Transverse Mercator) preserve local angles and shapes.
  • Equal Area projections (Albers) are essential for statistical heat maps.
  • The Universal Transverse Mercator (UTM) system divides the US into 6-degree longitudinal zones.
  • The Polyconic projection was the historical standard for USGS quadrangle maps.

Frequently Asked Questions

Why is the Albers Equal Area projection used for US maps?

It minimizes distortion of area between the standard parallels, making it ideal for the continental US where accurate size comparison between states is necessary.

What is the State Plane Coordinate System?

It is a set of 120+ geographic zones used for local surveying in the US. Each zone uses a specific projection (usually Lambert or Transverse Mercator) to ensure high accuracy within that zone.

Why does Alaska look huge on some maps?

Maps using the Mercator projection stretch areas significantly as they approach the poles. Since Alaska is at a high latitude, it appears much larger than it truly is relative to the lower 48 states.

What projection does Google Maps use?

Google Maps uses Web Mercator (EPSG:3857). It is computationally efficient and preserves angles (making turns 90 degrees), but it distorts size significantly at high latitudes.

What is a UTM zone?

UTM (Universal Transverse Mercator) divides the world into 60 zones, each 6 degrees of longitude wide. The US spans roughly 10 of these zones.

GeoQuizzy.com • Map Projections Used in US Mapping Quiz

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