1.Map projection is a way to transform the earth's spherical surface into a flat map. Map projections are
necessary for mapmaking.All map projections distort the surface in some fashion. There are hundreds
of different map projections. The process of transferring information from the Earth to a map causes
every projection to distort at least one aspect of the real world – either shape, area, distance, or
direction.
Map projection process is accomplished by the use of geometry and by mathematical formulas. In
geometric terms, the Earth is considered an undevelopable shape, because, no matter how the Earth is
divided up, it cannot be unrolled or unfolded to lie perfectly flat. Some of the simplest projections are
made onto geometric shapes that can be flattened without stretching or distorting their surfaces. These
shapes or forms are considered to be developable. Examples of shapes that reflect these properties are
cones, cylinders, and planes.Most projections are derived from mathematical formulas, but some are
easier to visualize as projected on to a developable surface. Therefore, projections are commonly
classified according to the geometric surface from which they are derived: conical, cylindrical, and
planar.
These geometric shapes can either be tangent or secant to the spheroid. In the tangent case the cone,
cylinder or plane just touches the Earth along a single line or at a point. In the secant case, the cone, or
cylinder intersects or cuts through the Earth as two circles. Whether tangent or secant, the location of
this contact is important because it defines the line or point of least distortion on the map projection.
This line of true scale is called standard line.
In the conical case, we can visualize the Earth projected onto a tangent or secant cone, which is then
cut lengthwise and laid flat. The parallels (lines of latitude), are represented by concentric circular arcs,
and the meridians (lines of longitude), by straight, equally spaced, radiating lines.This type of
projection is used for mapping midlatitude regions, such as Canada and the United States. The result is
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '11
 sands
 Map projection, crude death rate, CRUDE BIRTH RATE

Click to edit the document details