CHART PROJECTION

1. Chart Projection
COASTAL NAVIGATION AND
CHART WORK
UN 103

2. Projection: A method by which the curved surface of the earth is represented
on a flat surface.

3. The Desirable property of the preferable projection
1- keep the natural object shape on earth equivalent
2- keep the angular relation between the object equivalent to the real
3- well represent the area as the actual
4- provide a fixed scale to measure the distance
5- Great circles appear as straight lines
6- the rump line appear as straight lines
 Earth is in fact flattened slightly at the poles and bulges somewhat at the
equator.
 Mathematical Shape of the earth : An Ellipsoid, A geometrical figure which
would be obtained by rotating an ellipse about its shorter axis.

4. The requirement of a chart appropriate for maritime navigation
1-flat surface
2-The figure that is seen on the Earth is exactly the same as the
that is seen on the map
3- the rump line appear as straight lines
4- Possibility to measure course line, directions, and distances
5- Possibility to locate the ship’s position latitude and longitude.

5. Type of projection
1- CONVENTIONAL PROJECTION
AN EXAMPLE OF THIS
PROJECTION IS THE MOLLWIEDE
PROJECTION

6. Pros:
•Gives a more accurate visual
•Improved map, following the Robinson
•Less distortion, more proportional
Cons:
•No line of latitude or longitude represents accurate
location
•Poor directional map
Mollweide Projection

7. projection derived from cone
Conic Projections
Azimuthal Projections
Cylindrical Projections

8. Conic Projections
A conic projection is derived from the projection of the globe onto a cone placed over it. For the normal aspect, the
apex of the cone lies on the polar axis of the Earth. If the cone touches the Earth at just one particular parallel of
latitude, it is called a tangent. If made smaller, the cone will intersect the Earth twice, in which case it is called secant.
Conic projections often achieve less distortion at mid- and high latitudes than cylindrical projections. Further
elaboration is the polyconic projection, which deploys a family of tangent or secant cones to bracket a succession of
bands of parallels to yield even less scale distortion. The following figure illustrates conic projection, diagramming its
construction on the left, with an example on the right (Albers equal-area projection, polar aspect).

9. Some widely-used conic projections are
•Simple projection
•Lambert conformal projection
•Polyconic projection
•Simple projection
The simple conic projection is used in mapping
small areas near the line of tangency.
1
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‫كاملة‬ ‫غير‬ ‫دائرة‬ ‫شكل‬ ‫على‬ ‫يظهر‬ ‫القطب‬
‫االستدارة‬
2
-
‫خطوط‬ ‫شكل‬ ‫على‬ ‫تظهر‬ ‫الطول‬ ‫خطوط‬
‫المخروط‬ ‫قمة‬ ‫من‬ ‫تشع‬ ‫مستقيمة‬
3
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‫دوائر‬ ‫شكل‬ ‫على‬ ‫تظهر‬ ‫العرض‬ ‫خطوط‬
‫االستدارة‬ ‫كاملة‬ ‫غير‬

10. Lambert Conformal Conic Projection
The Lambert conformal conic map projection is
typically based on two standard parallels, but it can
also be defined with a single standard parallel and a
scale factor. It is best suited for conformal mapping of
landmasses extending in an east-to-west orientation
at mid-latitudes. This projection was rarely used
before the First World War but is now commonly used
for official topographic mapping around the world. The
state plane coordinate system uses it for all zones
that have a predominant east-west extent.

11. •Polyconic projection
A conic map projection having distances between meridians along
every parallel equal to those distances on a globe. The central
geographic meridian is a straight line, whereas the others are curved
and the parallels are arcs of circles.

12. Azimuthal Projections
An azimuthal projection is a projection of the globe onto a plane. In the polar aspect, an azimuthal projection maps to a
plane tangent to the Earth at one of the poles, with meridians projected as straight lines radiating from the pole, and
parallels shown as complete circles centered at the pole. Azimuthal projections (especially the orthographic) can have
equatorial or oblique aspects. The projection is centered on a point either on the surface, at the center of the Earth, at the
antipode, some distance beyond the Earth, or at infinity. Most azimuthal projections are not suitable for displaying the
entire Earth in one view, but give a sense of the globe. The following figure illustrates azimuthal projection, diagramming it
on the left, with an example on the right (orthographic projection, polar aspect).

13. Stereographic projection
This considers an opposite extreme point in the globe. The most common
are used as a reference, although in that case it would be called polar
It is also characterized because the parallels become closer as they go
circle is reflected as a semicircle or as a straight line.
Orthographic projection
It is used to have a vision of the hemispheres but from the perspective of
form are distorted and the distances are real, especially those that are around
Gnomonic projection
In this projection all the points are projected towards a tangent plane,
Earth.
It is usually used by navigators and pilots because the circular patterns of the
straight lines, showing shorter routes to follow.
It should be noted that although there are technological advances through
routes, the use of paper still persists.
type of azimuthal projections

14. Gnomonic projection
• Gnomonic: light projected from center of globe to
projection surface.

15. Stereographic projection
• light projected from
antipode of point of tangency

16. Orthographic projection
Orthographic: light projected from infinity

17. cylindrical projections