1. Lab 1: Projection Yingjie Hu

2. What is a projection? A projection is the rendering of the earth’s round, three-dimensional surface onto a flat map. Projection

3. What do we need to make a projection? A surface A method to project the features of the earth on our surface

4. Surface Plane surface Azimuthal projection (planar projection)

5. Surface Cylinder Cylindrical

6. Surface Cone Conic

8. How to project? Surface aspect Equatorial

9. Surface aspect Transverse

10. Surface aspect Oblique

11. Surface aspect Polar

12. Tangency Definition – Location at which the projection surface and the globe touch.

13. Secancy Definition – Location at which the projection surface cuts through the globe

14. Distortion The earth has a curved surface. When transforming the round globe to a flat surface, we will inevitably lose accuracy at places where the “paper” doesn’t touch the globe.

15. Map properties Conformality (Conformal projection) – Retention of correct angles on a map – Retaining the shapes and directions of the features on the earth – Lose the accuracy of area – Applied in navigation

16. Map properties Equivalence (Equivalent projection) – Retention the accuracy of the area on a map – Lose shape and direction of the features on the globe – Applied in area calculation

17. Map properties Compromise projections – Neither conformal nor equivalent – Avoid extreme distortion of one map property

18. Map properties Short summary – Distortion is inevitable, since the globe is round while paper is flat. – Preserving one property (shape) results in the distortion of another property (area). – Conformality retains shape and direction, but it loses area accuracy. Equivalency has the opposite properties.

19. How can we get the projection information from a map? Surface type – From the shapes constituted by longitudes and latitudes Cone

20. How can we get the projection information from a map? Surface type – From the shapes constituted by longitudes and latitudes Cylinder

21. How can we get the projection information from a map? Surface type – From the shapes constituted by longitudes and latitudes Plane

22. How can we get the projection information from a map? Surface aspect – From the area focused by the map Polar

23. How can we get the projection information from a map? Surface aspect – From the area that has the least distortion. Equatorial

24. How can we get the projection information from a map? Surface aspect – From the area that has the least distortion. Transverse

25. How can we get the projection information from a map? Surface aspect – From the area that has the least distortion. Oblique

26. How can we get the projection information from a map? Conformality – The shape is preserved. – The area of the features is distorted.

27. How can we get the projection information from a map? Equivalence – The area is preserved. – The shape of the continents is distorted.

28. Assignment All the materials are on Gauchospace. Answer all the questions, print your answer sheet, and submit it in the next lab class. Due date: Oct. 6 th (Next Thursday). Homework which is turned in late will lose 10% of the full score each weekday. Homework which is submitted after 5 weekdays will not be accepted.