Lab 1: Projection Yingjie Hu

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

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

Surface Plane surface Azimuthal projection (planar projection)

Surface Cylinder Cylindrical

Surface Cone Conic

How to project? Surface aspect Equatorial

Surface aspect Transverse

Surface aspect Oblique

Surface aspect Polar

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

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

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.

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

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

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

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.

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

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

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

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

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

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

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

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

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

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.