NAVIGATION – NAV 2104 LECTURE 3: INTRODUCTION TO CHART PROJECTION MOHD ‘ARIFF BIN ABDUL JALIL

INTRODUCTION  To become knowledgeable in geography and plotting, an understanding of maps, charts, and projections is extremely helpful.  A map or chart is a representation of a part of the Earth’s surface.  Certain factors have to be taken into account when constructing a map or chart.  A map is normally a representation of an area of land, giving details that are not required by the aviator.

Introduction  A map is a graphic representation of selected features of the Earth's surface, drawn to scale.  A map is a compact data base an information storage and retrieval system-that does not require machine action.  Instead, the skilled map reader retrieves information from the map. MAP

 The graphic representations on maps may consist of: MAP  lines and symbols of various colors;  drawings of landforms, called physio­graphic diagrams;  photographs with the addition of lines and colors to emphasize features

Example of Map MAP

Properties of ideal map  The ideal map should satisfy two requirements below: (a) Representation of the earth surface 1. Topography should be represented in its true shape 2. An angle on the earth surface should be represented by the same angle on the map 3. Scale should be constant and correct 4. Equal areas on the earth surface should be shown as equal on the map

MAP (b) Navigation Requirement 1. Rhumb lines should be straight 2. Great circle should be straight 3. Coverage should be world wide 4. Adjacent sheet should be fit accurately 5. Co-ordinates should be easy to plot.  But 2 of above can never be obtain which are:  scale can never be constant  Shape of larger area can never be represented accurately  Other - can be obtain - but not on the one map.

Chart Introduction  A chart is a special-purpose map, generally designed for a form of navigation, such as air navigation.  There is a difference between charts and maps.  Maps show land areas, political subdivisions, and topography.  A chart details water areas and has reference lines on it to allow the navigator to graphically plot information.

 A hydrographic chart provides information such as water depths and locations of navigational aids.  An air navigation chart may show land, but it provides the air navigator with elevations as well as the locations of navigational aids. Chart Thus, in aviation, we’ll use the term of CHART instead of MAP.

Chart – Ideal Properties Properties of the Ideal Chart  The ideal chart would have the following properties:  Constant scale over the whole chart  Areas of the Earth would be correctly represented (Conformal – see definition later)  Great circles should be straight lines  Rhumb lines should be straight lines

Continue...  The ideal chart would have the following properties:  Position should be easy to plot  Charts of adjacent areas should fit exactly  Each cardinal direction should point in the same way on all parts of the chart  Areas should be represented by their true shape

 The ideal chart is an impossibility. For navigation it is important that:  Bearing and distance are correctly represented  That both are easily measured  That the course that is flown is a straight line  Plotting of bearings should be simple  To get these properties other ideal properties have to be sacrificed. Chart – Ideal Properties

 On any chart certain properties cannot be achieved over the whole chart which are:  Scale is never constant and correct over large areas  The shape of an area can never be fully correct  Since it is very complicated to the ideal chart, therefore several techniques were used which is called CHART PROJECTION. Chart – Ideal Properties

The need of Ideal Chart  In navigation (especially for dead reckoning), navigators operate purely base on calculation.  Chart is usually use as the main reference for dead reckoning navigation process.  Chart is the real representation of the earth. Thus all information must be correct and accurate.  Thus, the ideal chart is needed to make sure we can navigate safely and efficiently.

 All charts were made in constant scale. This is to ensure the calculation will be tallied with the chart location.  If chart’s scale is not constant, upon calculation; we might found that the location (calculated) is the not same with the location referred to chart. The need of Ideal Chart

 Each cardinal direction should point in the same way on all parts of the chart.  As you notice, in all charts there will be lines of latitude and longitude (stated in degree).  In navigation, we refer to the location of latitude and longitude. If the cardinal direction is not same, confusion will happen.  Not only that, we’ll end up at different location since the cardinal direction is not the same as we want to. The need of Ideal Chart

Chart Projection  To portray the curved surface of the earth on a flat sheet of paper, a technique known as projection is used.  A projection is a method of representing a three- dimensional object on a two-dimensional surface.  It is impossible to project a three-dimensional object upon a two-dimensional surface without distortion.  Distortion cannot be avoided, but it can be controlled.

Chart Projection

 There are lots of types of projection available and each has its own properties, advantages, and disadvantages.  In any projection, they establish a network of lines corresponding to geographic coordinates.  The projection methods used are:  Cylindrical projections  Cone projections  Gnomonic projections and many more Chart Projection