# Notes: Fri 6 Sept

## Maps

latitude: angular measure in degrees from equator
longitude: angular measure in degrees from the prime meridian, Greenwich, England

Lying with Maps
There's no way to go from a 3-d globe to a 2-d continuous surface without some kind of distortion. Either the shape or area of land masses is distorted. The Mercator projection minimizes distortion of shape, but area is very distorted at poles (do you understand why?). Equal area projections like the Peter's projection from lab 1 keep the amount of surface area of land masses in proportion but the shapes look distorted. You can pick projections and map features to emphasize some feature you desire.

Q: How is the satellite photo of Earth lying?
A: no clouds at all, daytime everywhere, false-color imaging.

(also shown was a nighttime satellite image of the world)

When looking at a map for the first time, consider:
1) scale
2) type of projection
3) symbols and what they are depicting

(we looked at several maps of Florida in the book. Figures 3-10 & 3-11 are examples of isoline maps, or contour maps)

Distances
Shortest distance between 2 points on a sphere (like the Earth) is a great circle. A great circle is a line that would cut the Earth in equal halves, like cutting an orange in two. They are like lines of longitude except they don't have to cut through the poles. In contrast, a small circle is like a line of latitude, except it doesn't have to be parallel to the equator. It is similar to chopping off a slice of an orange, but not necessarily with the navel in the middle of the slice.

Rhumb lines are lines of constant compass direction. These lines are deceptively short on 2-D maps. They only look short because the scales on 2-D maps keep changing with latitude. If you used the map scale at every point of the "short" path, you'd find that in real life, the ground length would be bigger than the great circle path. On a 2-D map, great circle paths often look longer than Rhumb lines, but that is just an effect of the scaling. Also, your bearing, or compass direction, will change along a great circle path.