1. Types of Maps Mercator Projections Conic Projections
Gnomonic Projections
Geologic Maps
Topographic Maps
A map projection is a method for taking the curved surface of the earth and displaying it on something flat, like a computer screen or a piece of paper. Map makers have devised methods for taking points on the curved surface of the earth and "projecting" them onto a flat surface. Imagine a light inside a globe projecting out onto a piece of paper. These methods enable map makers to control the distortion that results from creating a flat map of the round earth.
There are 3 main types of map projections: Mercator, conic (& polyconic) + gnomonic
Geologic maps are made by the USGS (United States Geological Service) and they are mainly used to show rocks in a specific area
Topographic maps are used to show changes in elevation. They can be used to find rivers, lakes and other useful topographic features.

2. Mercator Projections Mercator Projection
Is a map that has parallel lines of longitude and latitude
Flaws
Land Near Poles is exaggerated
Shapes are correct, but land area is distorted
Mercator projection information is located on page 34 of the Earth Science book.
The further apart the lines are, the more distortion there is.
The longitudinal meridians are equally spaced while the parallel latitude lines are unequally spaced.
This uneven spacing of the latitude lines has some advantages and some disadvantages.
Advantages include straight line compass direction, latitude & longitude are easily determined, + shapes of lands are shown correctly, historically making this map useful for navigation
Some disadvantages include the map distortion at the extreme northern & southern latitudes that will appear much larger than they are relative to the rest of the map & places like Alaska & Antarctica will appear much larger than they are.

3. Conic Projections Conic Projection
Is made by projecting points and lines from globe onto a cone.
Very Little Distortion, High Degree of accuracy
Best for Mapping Small Areas
Used to make road and weather maps
Conic and polyconic projections are found on page 35 of the Earth Science book.
This type of map has very little distortion at the point of contact & is very useful for small areas such as local roadmaps.

4. Gnomonic Projections Gnomonic Projections
is made by projecting points and lines from a globe onto a piece of paper that touches the globe at a single point
Distort Directions and Distance
Used For Plotting great Circle Routes (Airplanes)
Gnomonic projection map information is found on page 35 of the Earth Science book.
This map type also has very little distortion at the point of contact and is very useful for plotting air travel
Gnomonic projections are NOT commonly used for ground navigation.

5. Geologic Maps This is a geologic map of the water resources & rock types at LakeTahoe
Geologic Maps show the distribution, arrangement & types of rocks located below the soil
They also contain information about fault lines & other geologic features
Geologic maps are discussed on page 38 of the Earth Science book.
A geologic map or geological map is a special-purpose map made to show geological features. Rock units or geologic strata are shown by color or symbols to indicate where they are exposed at the surface. Water is normally blue.
Geologic maps contain information about fault lines (major breaks in rock) & other geologic features.
They show the distribution, arrangement and types of rock located below the soil.

6. Topographic Maps Topographic Maps
Detailed maps that show the hills and valleys of an area
Use Lines, Symbols, and Colors to represent change in elevation

7. Map Features- map scales & legends

8. Map Legends Include symbols for both man made and natural features
Specific Colors for Habitats
Green for Woods
Blue for Water

10. Map Scales Ratio of distance on a map to actual distances on the map
3 Types
Verbal: “one inch equals one mile”
Graphic: consists of a line that represents a certain distance on Earth
Fractional: one unit on map represents one unit on Earth
Large Ratio: map covering large area (minor detail)
Small Ratio: map covering little area (major detail)

12. Isolines
An isoline is a line connecting points
of equal value.

13. Examples of isolines: (The weather channel loves isolines!)
Isotherms: points of equal temperature
Isobar: points of equal barometric (air) pressure
Contour: (all over topo maps)
points of equal altitude
Concentration of chemicals
Anything else you can get a value for.
(The weather channel loves isolines!)

17. Rules for Drawing Isolines:
1. Isolines connect points of equal value. 5 5
10
10
10
10
15
15

18. 2. Isolines are gentle, curving lines- no sharp corners.5 5
10
10
10
10
15
15

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

20. 4. Isolines NEVER cross- this would mean that one point has two different values. Ex: one spot has two temperatures?
60 °
50 °
40 °
30 ° X
20° Z Y

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

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

24. A gentle (low) gradient changes slowly and the lines are far apart.
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

25. Highlight data points.

26. Fill in gaps in data. This is hard. You have to do a best guess.

27. Connect the dots. Use rounded lines, nothing sharp pointed.

28. Go on to the next value until done with map
Go on to the next value until done with map. Remem-ber that contour lines are rounded