Introduction to GIS Cartographic Principles

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Questions and Answers

What is the primary purpose of map projections?

To enhance the aesthetic quality of maps

To create digital maps for navigation

To demonstrate geographic information systems' capabilities

To convert features from a three-dimensional surface onto a two-dimensional surface (correct)

Which type of map projection preserves the correct area of features?

Equal-Area Projections (correct)

Conformal Projections

Cylindrical Projections

Azimuthal Projections

What characteristic do Conformal Projections maintain?

Correct shape over small areas (correct)

The proportion of land to water

Correct area depiction

Straight lines as curved lines

How is an Orthographic projection constructed?

By tracing parallel rays from the globe onto a flat surface Signup and view all the answers

What differentiates the Stereographic projection from other projections?

It uses radial rays for tracing Signup and view all the answers

Which projection method involves wrapping the Earth in a cone?

Conic Projection Signup and view all the answers

What is one of the key reasons various map projections are developed?

To address the limitations of representing a sphere on a flat surface Signup and view all the answers

What assumption underlies the construction of all map projections?

A specific viewpoint is adopted Signup and view all the answers

What is the problem of curvature of the earth

At least one of above Signup and view all the answers

What does distortion can affect?

All Signup and view all the answers

What is distortion?

all Signup and view all the answers

Wha would mixing projections in which combine maps without converting them into compatible projection cause?

Large error Signup and view all the answers

Which is not the common properties of projections?

Incorrect Scale (distance on projection/sphere) Signup and view all the answers

What satellite now determine Earth shape?

NAVSTAR GPS Satellite Signup and view all the answers

What is the assumption of mapping?

Earth surface is highly regular Signup and view all the answers

What determine the projection of the Earth when mapping?

Accuracy one need Signup and view all the answers

Study Notes

Introduction to GIS Cartographic Principles

Geodesy is the scientific discipline that determines the size and shape of Earth.
Early maps depicted a flat Earth, but Aristotle (384-322 BC) argued for a spherical shape.
Aristotle calculated Earth's circumference to be 45,500 miles (approximately 24,902 miles).
Eratosthenes (around 250 BC) used the angles of the sun's rays to estimate Earth's circumference, arriving at a comparable value (approximately 25,000 miles).
Modern measurements show that Earth is not a perfect sphere, it is an oblate spheroid, slightly flattened at the poles and bulging at the equator.
The NAVSTAR GPS satellites accurately determine Earth's shape.
A geoid represents a smoothed representation of Earth's topography on top of an ellipsoid.
Map projections convert a three-dimensional (3D) sphere or ellipsoid to a two-dimensional (2D) flat representation. This transformation always results in some distortion.
The choice of projection depends on the desired accuracy.

Presentation Outlines

Geodesy and size of Earth
Map Projections
- What is a projection?
- Distortion of map presentation
- Planar projections
- Conical projections
- Cylindrical projections
- Reasons for using projections
Coordinates: a 2D mapping framework
Issues with map projections - The Problem of Curvature of Earth
Types of Map Projections
- Azimuthal/Planar Projections
- Conic Projections
- Cylindrical Projections
- Equal-Area Projections
- Conformal projections
Common properties of projections
- Equidistant
- Equal Area
- Orthomorphic/Conformal
Summary
Practical considerations

Mapping Framework

Maps are 2D representations of a 3D Earth.
Locating positions on Earth involves a 2D coordinate system.
Easting and northing are used to locate locations across the Earth surface.
Elevation (the third dimension) is often included relative to a datum. (Mean sea level).

Map Projections

Map projection: a mathematical process to transfer Earth's features from a sphere ( or ellipsoid) onto a flat surface.
Projections cause distortion.
Choosing an appropriate projection is important, as different projections will provide different levels of accuracy for various map elements.
Common projections methods include planar, cylindrical and conic.

Distortion of Map Presentation

Distortion represents inaccuracies in angles, shapes, distances, and areas when transferring a curved surface (Earth) to a flat surface (map).
Every projection has a unique distortion pattern.
Understanding and minimizing distortion is crucial in cartography.
Methods used include cones and cylinders to create surfaces with zero curvature.

Problem of Curvature of The Earth

The Earth's curved surface presents a challenge for mapping.
Transferring this curvature to a flat map always results in some degree of inaccuracy (distortion) in distance, direction, area or shape.

Unavoidable Distortion

All map projections inevitably distort the true shape of the Earth.
Distortion can affect conformity (consistency of scale), shape, direction, area, and scale relative to the curved surface of the Earth.

Summary

Geodesy has a complex history, with early attempts to map Earth being inaccurate due to flat Earth assumptions.
Earth shape is usually approximated as an oblate spheroid (ellipsoid) for mapping.
Map projections transform a 3D Earth to a 2D map, leading to inherent distortions.
Projections can be planar, cylindrical, or conical.
All projections introduce some degree of error.

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Description

This quiz explores fundamental concepts in GIS cartographic principles, including the history of Earth's measurements and different types of map projections. Understanding geodesy and the implications of Earth's shape on cartography is crucial for accurate mapping and geospatial analysis.