Physical Science 101
Maps and Location Systems
What is a map?
Graphic representation of a given area - a drawing
Language of Maps:
Problem: How do we represent the surface of a sphere on a map?
- direct representation - no distortion
- limited in size
- not easily transported or moved
2. Flat Sheets
Problem with a flat sheet is that it is not possible to flatten a sphere without distorting the surface
- Undevelopable geometric figure -cannot be flattened without distortion.
- Developable geometric figure- can be flattened without distortion: cylinder, cone, plane
Projection of the surface of a sphere onto a developable surface
- imagine a lightbulb at the center of the sphere and the lines on the sphere casting shadows on the surface of a developable figure
Plane in contact with one point of the sphere
Polar Projection is most common type
Cone apex is located directly above the pole
best for mid-latitude maps
Cylinder oriented parallel to axis
Mercator Projection is most well known
- developed by Gerhardus Mercator, Flemish cartographer. It has the property that any straight line drawn on the surface has a constant compass bearing - used in naval navigation
Interupted and Condensed Projections
Broken surface projection
Condensed projection- unneeded parts are omitted.
Map Location Systems
Global System - Longitude and Latitude
1. Longitude lines - "Meridians" - "Great Circles"
- north-south lines on the globe - all intersect at the North and South Poles
- measured in degrees East and West of the Prime Meridian
2. Latitude lines - "Parallels"
- East-West lines on the globe
- measured in degrees North and South of the Equator
Basic Map Information
All maps should contain the following information
Title - clearly and concisely describes the map location
Date - indicates the date of publication or revision
Location - Longitude and Latitude; Public Land Survey System; Inset Map.
Directional Orientation - Compass direction - if no compass direction is given, the standard convention is that north is at the top of the map
Legend - Information on the symbols used on the map
a. Ratio Scale -ex. 1:24,000 - 1 inch on the map = 24,000 inches on the ground
b. Bar Scale - allows direct measurement of the ground distances
Some of the Major Types of Maps
• Environmental - Landscape, Vegetation, Precipitation, Climatic, etc.
• Geographic Maps - Political, Country, State, Local, City, Highway, Road
• Statistical - Population, Economic