This document discusses map projections, which are methods for representing the curved surface of the Earth on a flat plane. It covers the differences between globes and maps, the developable versus undevelopable surfaces, and various ways of classifying map projections based on their construction method, developable surface, orientation, desired attributes preserved, and viewpoint or light source location. The key types of map projections mentioned are cylindrical, conical, zenithal, perspective, and non-perspective projections.

1. Map Projections
By
MOHAMMAD
NAZIR

2. Map Projection
• Any method used to represent curved
surface of the earth on a plane.
• Means of representing geographic
coordinates as Cartesian coordinates

3. Representation of the earth
Globe(3-D) Map(2-D)
•Preserves areas, scales,
distances and directions.
•Expensive to produce
•Difficult to reproduce
•Cumbersome to handle
•Awkward to store
•Difficult to measure
•Half of the globe is visible at one
time.
•Causes distortions in shape, area
and size
•More compact and easier to store
•Viewed easily on computer
displays
•Facilitate measuring properties
•Show large portion of earth at
once
•Cheaper to produce and
transport
•Useful traits of map motivate the
development of map projections

4. Developable and undevelopable
surface
• A surface that can be unfolded or unrolled
into a flat plane or sheet without
stretching, tearing or shrinking is called a
developable surface.
• Sphere and ellipsoid are undevelopable
surfaces
• Any projection that attempts to project a
sphere on a flat sheet will distort the
image.

5. Classification on the basis of
method of construction
• Perspective
• Non-perspective

6. Non-perspective map projections
• They do not use a conceptual generating a
globe. Such projections represent an
arrangement of parallels of latitude and
meridians of longitudes in conformity with
some mathematical calculations. They are
known as geometric, conventional,
pseudo-cylindrical or non-perspective map
projections.

7. Perspective map projections
• Some surface is positioned near, on or in
the earth and rays go through the earth
leaving a shadow on the earth surface

8. Classification on the basis of
developable surface
• Cylindrical
• Conical
• Zenithal

9. Classification on the basis of
orientation of the shape
• Once a choice is made between projecting onto a
cylinder, cone or plane, the orientation of the shape must
be chosen. The orientation is how the shape is placed
with respect to the globe. The orientation of the surface
may be:
• Normal (in line with the earth axis)
• Transverse (in respect to normal rotated by 90°)
• Oblique (any angle in between the normal and the
transverse case)
• Tangent (developable surface touches the globe along
one line)
• Secant (developable surface touches the globe along
two lines)

12. Problems of transformation
• Scale factor (Distance)
• Shape
• Area
• Direction

13. Classification on the basis of
desired attributes
• Homolographic or equal area
(Preservation of areas)
• Orthomorphic or conformal (Preservation
of shape)
• Equidistant (Distance preservation)
• Azimuthal (Direction preservation)

14. Classification on the basis of view
point or light source location
• Gnomonic (Light placed at the centre of
the globe)
• Stereographic (Light placed at the
antipode)
• Orthographic (Light placed at infinity)

15. Choice of Map Projections
• The extent of the area to be represented
• The purpose for which the map is mainly
required