This document defines map projections and their basic concepts. It discusses that map projections are a means of depicting the earth's spherical surface on a flat plane. The key aspects covered are: - Map projections transform the 3D globe onto a 2D surface through a process of generating a globe and projecting it onto a plane. - The projection plane can be planar, cylindrical, or conical based on the surface used. Different properties are maintained based on the type of projection. - Common map projections in use include the Universal Transverse Mercator, Polyconic, Lambert Conformal Conic, and Stereographic projections.

1. MAP PROJECTION: Basic Concepts
Dr. Lila Mahato
Post Graduate Department of Geography,
Krishnagar Govt. College, Nadia, West Bengal

2. MAP PROJECTIONS
Characteristics of maps
Definition of map projection
Generating Globe
Projection Plane (nature and Aspect),
Developable Surface
Properties of Projection
Classification of Map Projection

3. MAP – Nature and characteristics
 Graphic representation of the geographical setting i.e. Communicate geographical
information graphically
 Printed depiction of the Earth’s surface as a whole or part of it on a plane sheet of
paper.
So,
• All geographical maps are reductions. --Scale.
• All maps involve geometrical transformations. -- Map projection.
• All maps are abstractions of reality.
• All maps use signs to stand for elements of reality.
Cartography is the making and study of maps in all their aspects. It is an efficient way of
manipulating, analysing and expressing ideas, forms and relationships that occur in
two- and three-dimensional space.
Processes in Cartography
• Collecting and selecting the data for mapping
• Manipulating and generalising the data, designing and constructing the map
• Reading or view the map
• Responding to or interpreting the information

4. GENERATING GLOBE
It is a Globe from which the projections are to be
developed.
It is looked upon as a glass or wire skeleton Globe on
which the meridians and parallels are marked.
N
S
EW O
PROJECTION – Imposition of an object on any other surface with a particular
viewpoint or perspective.
MAP PROJECTION :
 is a means of drawing of Earth’s surface on a plain sheet of paper
 drawing of Graticules ( net of lines of Latitudes and meridians of Longitudes)
 transformation of 3 dimensional Globe on a 2 dimensional plane.

5. The map projection process: the sphere, approximated by a mathematical figure is
reduced to a generating globe that is projected on a flat surface.
(after Canters and Decleir 1989)

6. DEVELOPABLE SURFACES
A surface that can be made flat by cutting it along certain lines and
unfolding or unrolling it.
Cones, Cylinders, & Planes are all developable surfaces.
• Cones = conical projections
• Cylinders = cylindrical projections
• Planes = planar projections

7. Nature of Projection Planes
PROJECTION PLANE
The plane that touches the generating Globe at a point.
This point of tangency is truly represented on projection.
It may be a plane , a cylinder or a Cone

8. Map Projection: Characteristics
The following properties would be present on map projection
•Areas are everywhere correctly represented
•All distances are correctly represented.
•All directions on the map are the same as on Earth
•All angles are correctly represented.
•The shape of any area is correctly represented
It is, unfortunately, impossible to have all these properties together in one
map projection.

9. Classification of Projections
A. On the basis of Viewpoint of Map Projection- 1. Perspective
2. Non- Perspective
B. On the basis of Nature Projection plane - 1. Planar
2. Cylindrical
3. Conical
4. Conventional
(Mathematical)
C. On the basis of properties maintained in the Projection –
1. Equidistant
2. Equal Area
3. Orthomorphic
4. Azimuthal
5. Aphylactic
Contd..--

10. D. On the basis of Aspect of the Projection Plane –
1. Normal Case
2. Equatorial Case (Transverse)
3. Obilique Case)
Contd..--

11. E. On the basis of the position of the source of Light – 1. Gnomonic
2. Stereographic
3. Orthographic

12. Standard Parallel

13. Map Projection in Common Use
Several hundreds of map projections have been described in several
books. But, most commonly used map projections are:
A. Universal Transverse Mercator (UTM)- The UTM is a secant,
cylindrical projection in a transverse position
B. Polyconic- early maps in the International Map of the World
(1:1,000,000 scale) series and for topographic mapping in some
countries.
C. Lambert Confomal Conic
D. Stereographic projection.