About map projection in GIS

2. Projecting is a science of converting spherical earth
surface to a flat plane

3. Introduction
 No system can do this perfectly some distortion will
occur
 Properties that distorted are angle, areas, directions,
shape
 The term projection comes from the placing a light
source inside the globe and projecting the shadows of
the meridians and geographic features of globe.
 Cartographers is one who prepares the maps.

4. types of projection
 Cylindrical projection
 Conical projection
 Planar or Azimuthal Projection

5. Families in projection

6. Cylindrical projection
A cylinder is assumed to circumscribe a
transparent globe, so that the cylinder touches the
equator throughout its circumference. Assuming
that a light bulb is placed at the centre of the globe
is projected onto the globe, the graticle of the
globe is projected onto the cylinder. By cutting
open the cylinder along a meridian and unfolding
it, dividing into 360 equal parts.

8. Conical projection
 A cone is placed over a globe in such a way that the
apex of the globe is exactly over the polar axis. A cone
must touch the globe along a parallel of latitude,
known as the standard parallel, scale is correct and
distortion is the least. When the cone is cut open
along a meridian and laid flat, a fan shaped map is
produced

10. Planar projection
 Planar projection is also
called azimuthally projections, project map data onto
a flat surface. The simplest planar projection is
tangent to the globe at one point. Although the point
of contact may be any point on the earth's surface, the
north and south poles are the most common contact
points for most GIS databases. Other locations are
used primarily for specific applications, such a
navigation or locational inset maps.

12. Distortion in map projection
All map projections involve some degree of
imprecision or distortion in one or more of the
characteristics of the globe
size (area) of land and water masses
shape of land and water masses
distance between two points
direction (N, S, E, W)

13. Common map projection
The Robinson projection is a map projection of
a world map which shows the entire world at once. It
was specifically created in an attempt to find a good
compromise to the problem of readily showing the
whole globe as a flat image

15. Mercator projection
 The Flemish geographer and mathematician Gerardus
Mercator (2522-2594) designed his projection in 2569
as a navigational aid for sailors. He wanted a map on
which a compass heading or line of constant bearing
would appear as a straight line. This property would
allow navigators to transfer compass headings directly
to the map and to directly measure course headings
between points shown on the map.

17. UTM OF MERCATOR
 The Universal Transverse Mercator (UTM) conformal
projection uses a 2-dimensional Cartesian coordinate
system to give locations on the surface of the Earth. Like
the traditional method of latitude and longitude, it is
a horizontal position representation, i.e. it is used to
identify locations on the Earth independently of vertical
position. However, it differs from that method in several
respects.
 The UTM system is not a single map projection. The
system instead divides the Earth into sixty zones, each
being a six-degree band of longitude, and uses
a secant transverse Mercator projection in each zone.

19. conclusion
 Map projections and coordinate system in mapping are
important for position specification on the earth,
which is transferred to flat map. The coordinate
system enables us to know material’s point and
position on the earth through Meridian Line dividing
the earth into parts based on angular distance or
meridian called Geographic Coordinates.

20. Thank you