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1. Graticule
A graticule is a network of lines which can be used for
geographic plotting, scale, and focusing, depending on
the application.
sometimes described as a grid
A common example of a graticule is a grid of lines on a map
which corresponds to longitude and latitude.
4. Important properties of a projection
DistortionDistortion, great or small, is always present in at
least one region of planar maps of a sphere.
Distortion is a false presentation of angles,
shapes, distances and areas, in any degree or
combination.
5. ShapeShape
• Map projections that represents the true or correct
shape of the earth’s features are called conformalconformal
projections .projections .
• To preserve the shape, angles between the lines on
the reference globe should be maintained in the map.
• Usually these projections can show only small areas
of the earth’s surface at one time.
6. Area
• ‘‘Equal area projections’Equal area projections’ are drawn so that they
illustrate the same representation of the area of the
feature.
• All mapped areas have same proportional relationship
to the areas on earth.
• sx
*sy
= 1, an increase in scale factor in one direction
must be compensated by decrease in the other
direction.
• Shape distortion
7. Distance
• Projections that attempt to minimize
distortions in measures of distance.
• No projection can measure distances
correct on the entire map.
• Maintain more standard lines.
• Important for travellers
8. Direction
• Lines of constant direction are called
rhumb lines or loxodromes.
• They are all curved except on Mercator
projection.
• Important for navigators.
9. Standard parallel and standard meridian
• A parallel or a meridian on a map or chart
along which the scale is as stated for that
map or chart.
• The standard line refers to the line of
tangency between the projection and the
reference globe.
• There is no distortion along this line
10. Different map projection criteria
Map projection
• according to the developable surface.
• according to the method of deviation
(source of light).
• according to the global properties
11. Developable surface
• Cones and cylinders are developable surfaces
with zero Gaussian curvature
• Distortion always occur when mapping a sphere
onto a cone or cylinder, but their reprojection
onto a plane incurs in no further errors.
12. Map projection
according to the developable surface
Conic ProjectionsConic ProjectionsConic ProjectionsConic Projections
Cylindrical ProjectionsCylindrical ProjectionsCylindrical ProjectionsCylindrical Projections
Polar or Azimuthal ProjectionPolar or Azimuthal ProjectionPolar or Azimuthal ProjectionPolar or Azimuthal Projection
18. Conic Projections
properties
• Meridians are straight lines, converging at a point.
Compared with the sphere, angular distance
between meridians is always reduced by a fixed
factor, the cone constant
• Parallels are arcs of circle, concentric in the point
of convergence of meridians. As a consequence,
parallels cross all meridians at right angles.
Distortion is constant along each parallel
19. Conic Projections
properties
• The distance between the meridians
decreases towards pole.
• Conic projections can represent only one
hemisphere at a time, either northern or
southern
20.
21.
22.
23. Equidistant Conic Projections
EquidistantEquidistant (also called simple) conic
projections are obtained by adjusting the
spacing of the parallels, so that they are
equally spaced along meridians and the
distance between the parallels on the map is
equal to the arc length between the parallels
on the generating globe
24. Equidistant Conic projection
• They are suitable for points in the vicinity of a
parallel on one side of Equator.
• Scale is the same along all meridians. Commonly
one or two parallels are chosen to have the same
scale, suffering from no distortion.
• It is neither equal-area nor conformal
26. Properties of simple conic projection
1. Parallels are concentric arcs of the
circles.
2. The pole is represented by an arc.
3. The meridians are straight lines and they
intersect the parallels at right angles.
4. The distance between the meridians
decrease towards the pole.
27. Uses of simple conic projection
1.Railways, roads, narrow river valleys and
international boundaries running for a long
distance in the east- west direction can be
shown on this projection.
2.Since the scale along the meridian is correct a
narrow strip along a meridian is represented
satisfactorily
28. • Axis of the cone does not
line up with polar axis of
globe is called obliqueoblique
29. Map projection
according to the developable surface
2. Cylindrical Projections
The globe is projected on to a cylinder that has its
entire circumference tangent to the Earth’s surface
along a great circle (e.g. equator).
The cylinder is then cut along the meridian and
stretched on to a flat surface
32. Properties of cylindrical projections
In the equatorial aspect (the most common, andIn the equatorial aspect (the most common, and
frequently the only useful) of all cylindrical projections:frequently the only useful) of all cylindrical projections:
• All coordinate lines are straight
• Parallels (by convention horizontal) cross meridians always at
right angles
• Scale is constant along each parallel, so meridians are equally
spaced
• All parallels have the same length; the same happens to
meridians
Therefore…..
33. Properties of cylindrical projections
• Whole-world maps are always rectangular
• Scale is identical in any pair of parallels equidistant from
Equator
• Scale differs considerably among parallels, reaching infinity
at poles, which have zero length on the Earth but are as long
as the Equator on a cylindrical map
34. cylindrical projectionscylindrical projections
• As a group, cylindrical projections are more
appropriate for mapping narrow strips centered
on a standard parallel.
• Although useful for comparison of regions at
similar latitudes, they are badly suited for world
maps because of extreme polar distortion.
35. Cylindrical equidistant projections
• The graticules are perfect squares, the
equator becomes a straight line of length
2 r and meridians are r long.
Graticules are standard in the North
South directions and along equator in the
East West direction.
π π
39. Mercator projection
• Flemish geographer Gerardus Mercator, in 1569.
• cylinder tangent to the equator and parallel to the
polar axis.
• lines of constant bearing, known as rhumb lines or
loxodromes, are represented as straight segments.
• It is a conformal projection
43. Properties of Mercator projection
1.Parallels and meridians are straight lines, and intersect at
right angles.
2. The distance between the parallels go on increasing
towards the pole, but the distance between the meridians
remains the same.
3. All parallels are of the same length equal to that of
equator.
4. The meridians are longer than the corresponding
meridians on the globe.
44. Limitations of Mercator projection
1. Since the scale in zones of high latitudes are
greater, the sizes of countries there are very
large.
2. Poles cannot be shown because the
exaggeration in scales along the 90 degrees
where the parallel and the meridian touch
them will become infinite.
45. Uses of Mercator projection
1. Used for navigational purposes both on the sea and
in air.
2. Ocean currents, wind directions and pressure systems
are shown, as the directions are maintained truly.
3. Since exaggeration in size and shape in tropical
regions is minimum, maps of tropical countries are
shown on this projection for general purposes.
46. Transverse Mercator ProjectionTransverse Mercator Projection
The cylinder is rotated 90° (transverse) relative to the equator
projected surface is aligned to a central meridian rather than to the equator
47. Characteristics of
Transverse Mercator ProjectionTransverse Mercator Projection
• The map is conformal,
• The central meridian is straight,
• Distances along it are proportionally correct, that
is, the scale is constant along the central meridian.
• since meridians are not straight lines, it is better
suited for large-scale topographic maps than
navigation
• Indian National grid system
48. Universal Transverse MercatorUniversal Transverse Mercator
(UTM)(UTM)
The UTM defines a grid covering the world between
parallels 84°N and 80°S.
The grid is divided in sixty narrow zones, each centered on
a meridian.
Zones are identified by consecutive numbers, increasing
from west to east
50. Map projection
according to the developable surface
3.Azimuthal Projections
AzimuthalAzimuthal (or zenithal) Projections are
projections on to a plane that is tangent to some
reference point on the globe.
54. Azimuthal Projections
• All azimuthal projections preserve the azimuth from a
reference point (the conceptual center of the map),
thus presenting true direction (but not necessarily
distance) to any other points.
• They are also called planar since several of them are
obtained straightforwardly by direct perspective
projection to a plane surface.
55. Azimuthal Projections
if one of the poles is the central point;
• meridians are straight lines, radiating regularly
spaced from the central point
• parallels are complete circles centered on the
central point
• projections are only distinguished by parallel
spacing .
• The outlines of maps are circular.
57. Azimuthal Orthographic Projection
• In this projection it is assumed that the light source is
at infinite distance from the point of tangency,
resulting in the ray of light being parallel to each other
and perpendicular to the projection surface
58. Properties of Orthographic Projection
1. Since the scale along the meridian decreases
rapidly away from the center, the shapes are
much distorted, the distortion increasing away
from the center of projection.
2. The parallels are concentric circles.
3. The meridians intersect the parallels at right
angles
59. Limitations of Orthographic Projection
• The shapes are much distorted near the margin
of the projection.
• The sizes of the areas are diminished away from
the center of projection.
• It is only a small area in the central part of the
projection that can be represented in a
satisfactory way
60. Azimuthal Stereographic Projection
An azimuthal
stereographic map
has a simple
geometric
interpretation:
rays emanating from one point pierce the Earth's
surface hitting a plane tangent at the point's
antipode
61. Properties of Stereographic Projection
1. The parallels are not spaced at equal
distances.
2. The scale along the parallels also increases
away from the center of projection.
3. Areas are exaggerated, the exaggeration
increase away from the center of projection.
62. Limitations of Stereographic Projection
• Since the areas are enlarged away from
the centre of projection only small area in
the central part of the projection can be
represented satisfactorily
63. Gnomonic Projection
The gnomonic (also called
central, or azimuthal
centrographic
the ray source is located
exactly on the sphere's
center
64. Properties of Gnomonic Projection
1. The parallels are concentric circles.
2. The meridians intersect the parallels at right
angles.
3. The scale along the parallels increases from
the center of projection.
4. The spacing of parallels are not equal
