Types of MapsMercator ProjectionsConic ProjectionsGnomonic ProjectionsTopographic Maps

Mercator ProjectionsMercator Projection

Is a map that has parallel lines of longitude and latitudeFlaws

Land Near Poles is exaggerated Shapes are correct, but land area is distorted

Conic ProjectionsConic Projection

Is made by projecting points and lines from globe onto a cone.Very Little Distortion, High Degree of accuracyBest for Mapping Small AreasUsed to make road and weather maps

Gnomonic Projections

Gnomonic Projectionsis made by projecting points and lines from a globe onto a piece of paper that touches the globe at a single pointDistort Directions and DistanceUsed For Plotting great Circle Routes (Airplanes)

Topographic MapsTopographic Maps

Detailed maps that show the hills and valleys of an areaUse Lines, Symbols, and Colors to represent change in elevation

Map FeaturesMap LegendsMap Scales

Map LegendsInclude symbols for both man made and natural featuresSpecific Colors for Habitats

Green for WoodsBlue for Water

See Appendix D on p. 914

Map ScalesRatio of distance on a map to actual distances on the map3 Types

Verbal: “one inch equals one mile”Graphic: consists of a line that represents a certain distance on EarthFractional: one unit on map represents one unit on Earth

Large Ratio: map covering large area (minor detail) Small Ratio: map covering little are (major detail)

IsolinesAn isoline is a line connecting points of equal value.

Examples of isolines:Isotherms:

points of equal temperature

Isobar:

points of equal barometric (air) pressure

Contour:

points of equal altitude

Concentration of chemicals

Anything else you can get a value for.

(The weather channel loves isolines!)

Rules for Drawing Isolines:

1. Isolines connect points of equal value.

15

5 5

1510

1010

10

2. Isolines are gentle, curving lines- no sharp corners.

15

5 5

1510

1010

10

3. Isolines are always closed curves even though the map might only show part of it.

4. Isolines NEVER cross- this would mean that one point has two different values. Ex: one spot has two temperatures?

20°

30 °

40 ° 50 ° 60 °

X

YZ

5. Isolines usually are parallel. (They have a parallel trend.)

Visualizations of contour lineshttp://geology.asu.edu/~sreynolds/topo_gallery/topo_gallery.htm

GradientGradient shows how quickly the value changes from one point to another.

Gradientvalue

dis c e

tan

A steep (high) gradient changes quickly and the isolines are close together.A gentle (low) gradient changes slowly and the lines are far apart.

Steep area

Gentle area

Making Contours worksheetsWorksheets can be printed from:http://www.rcmurphy.net/Medina%202005/documents/Contours123.doc

Highlight data points.

Fill in gaps in data.

Connect the dots.

Go on to the next value.

Making a Contour Map II

Drawing Contour Maps III