# EnggPedia - The Engineering Encyclopedia

Wed12042013

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# Map

Definition: A map is a graphic form, normally to scale, of spatial abstraction of features on, or in relation to, the surface of the Earth.

## Types of maps

1. Topographic maps
2. Thematic maps

### Topographic map:

A reference tool, showing the outlines of selected natural and man-made features of the Earth. ? "Topography" refers to the shape of the surface, represented by contours and/or shading, but topographic maps also show roads and other prominent features.

### Thematic map:

A tool to communicate geographical concepts such as

• The distribution of population densities, climate, movement of goods, land use etc.
• Line maps versus photo (image) map
• 2D vs 3D maps

## Characteristics of maps

• Scale
• Projection

### Scale

The scale of a map is the ratio between distances on the map and corresponding distances in the real world, e.g., if a map has a scale of 1:50,000, then 1 cm on the map equals 50,000 cm or 0.5 km on the Earth's surface.

"Small scale" and "large scale" is often confused, e.g, 1:50,000 vs. 1:500,000

The scale controls not only how features are shown, but what features are shown, e.g., Engineering building: 0.2mm*50,000=10 m? Map projections. The Earth's surface is curved but as it must be shown on a flat sheet, some distortion is inevitable.

### Projection

A projection is a method by which the curved surface of the earth is represented on a flat surface.

Numerous projections have been invented for various applications

• ?Cartographic abstraction ?- Selection of the few features in the real world to include classification of selected features into groups (e.g., bridges, churches, railways)
• Simplification of jagged lines (e.g., coastlines
• Exaggeration of features to be included that are to small to show at the scale of the map Symbolization to represent the different classes of features chosen

## Geographic (Geo-spatial) information

1. Information about places on the earth