An ellipsoid is a manipulated ellipse based on the region being projected. In essence, an ellipsoid is a sphere with flattened poles, and is considered much more accurate in mapping the earth.
2. What is the imaginary network of intersecting latitude and longitude lines on the earth's surface called?
Graticules
3. How does the magnetic north differ from the geographic North Pole?
The magnetic north pole is where compasses point to on earth whereas a geographic north pole is the pole on which the earth's axis rotates. They are not the same point.
4. Why are datums important? Briefly describe how datums are developed.
Datums serve as a reference for ellipsoids and geographical accuracy. They are composed of a specific ellipsoid and specific points on the earth that specify the surface of the earth.
5. What is a map projection?
A map projection is when the 3-dimensional surface of the earth is projected onto a 2-dimensional mapping area.
6. What is a developable surface?
Developable surfaces are geometric surfaces in which the earth can be projected onto. Some examples include cones, cylinders, and planes.
7. Which lines on the graticule run north-south, converge at the poles, and mark angular distance east and west of the prime meridian?
a. Lines of longitude
8. Which of the following ellipsoids is now regarded as the best model of the earth for the region of North America?
c. GRS80
9. Which well known coordinate system would be appropriate to use for developing and analyzing spatial data when mapping counties or larger areas? Why?
The state plane coordinate system would be best due to the fact that it increases in accuracy over larger and wider distances.
10. What is a great circle distance?
It is the distance between two points on the earth via the earth's curvature.
A map projection is the building block of the major 2D maps that we all use on a daily basis. They come in all types of forms, projected onto different shapes (circles, cylinders, planes) depending on the type of map being created and its purpose. A map projection's significance lies in its determining how accurate a map can be.
The type of projection one uses depends solely on what type of purpose the map is going to achieve. No matter which type of projection is used, there is always distortion to some extent, as the irregular shape of the earth cannot be 100% fully illustrated on a 2D surface. Thus, different types of projections were created.
The equidistant maps I used were the Sinusoidal and Platte Carree projections. The Sinusoidal map shrinks at the poles, in an attempt to sort of mimic the spherical shape of the earth, though the distortion is heavy at the poles. The Platte Caree projection equally spaces all meridians on the globe, making the higher latitudes wider than they actually are.
For my conformal maps, the Mercator exaggerates the sheer sizes of Greenland and Antarctica, making Greenland almost as big as North America! The Fall Stereographic is similar, but distortion at the poles is much less drastic. For these types of maps, only areas around the equator are visually accurate.
For the Equal Area maps, though the Bonne and Mollweide both encompass the same area, the Bonne's extreme bending of the poles actually brings Baghdad and DC closer together, in contraste with Mollweide.
No comments:
Post a Comment