Presentation on theme: "What is a projection? A map projection is used to portray all or part of the spherical Earth on a flat surface. This cannot be done without some distortion."— Presentation transcript:
1 What is a projection?A map projection is used to portray all or part of the spherical Earth on a flat surface. This cannot be done without some distortionEvery projection has its own set of advantages and disadvantages. There is no "best" projectionIn GIS we must select the one best suited to our needs, reducing distortion of the most important features3
2 MERCATOR (Cylindrical) Chart ProjectionsThree main typesLAMBERT (Conic)GNOMONIC (Azimuthal)MERCATOR (Cylindrical)6
3 LAMBERT (Conic) projections result from projecting a spherical surface onto a cone.6
4 LAMBERT (Conic) Projections Lambert Conformal Conic projectionArea, and shape are distorted away from standard parallels. Directions are true in limited areas. Used for maps of North America. Lambert Conformal Conic projections are used for rectangular zones with a larger east-west extent.Ex: North Carolina, Tennessee
5 GNOMONIC (Azimuthal)Azimuthal—Geometrically projected on a plane. Point of projection is the center of a globe.27
7 GNOMONIC (Azimuthal)Used by some navigators to find the shortest path between two points. Used in seismic work because seismic waves tend to travel along great circles.Any straight line drawn on the map is on a great circle, but directions are true only from center point of projection. Map is perspective (from the center of the Earth onto a tangent plane) but not conformal, equal area, or equidistant.Considered to be the oldest projection. Ascribed to Thales, the father of abstract geometry, who lived in the 6th century B.C.28
8 Mercator Used for navigation or maps of equatorial regions. Any straight line on the map is a rhumb line (line of constant direction).Directions along a rhumb line are true between any two points on mapGerardus Mercator ( )11
9 MERCATOR (Cylindrical) projections result from projecting a spherical surface onto a cylinder.
11 Features of MercatorDistances are true only along Equator, but are reasonably correct within 15° of Equator.Areas and shapes of large areas are distorted.Distortion increases away from Equator and is extreme in polar regions. The map is not perspective, equal area, or equidistant.Equator and other parallels are straight lines and meet meridians at right angles12
12 WHAT IS A NAUTICAL CHART? A Nautical Chart is a graphic portrayal of the marine environment.In addition to its basic elements, a chart is a working document used bythe mariner both as a "road map" and worksheet and is essentialfor safe navigation.
13 Chart ScaleThe size of the area represented in a chart varies in according to the scale of the chartCharts with a small scale will cover a large areaCharts with a large scale will cover a small area1/1/1/40.0001/11/1/
16 Haritanın Ulusal Numarası 2 Haritanın Seyir Yardımcılarına Uygun. 3 1319209121610NoAçıklaması1Haritanın Ulusal Numarası2Haritanın Seyir Yardımcılarına Uygun.3Haritanın Uluslararası Numarası9Köşe Koordinatları10Harita Başlığı veya Adı11Haritanın Projeksiyon Tipi12Haritayı Hazırlayan Kuruluşun Amblemi13Haritanın Öşçeği15Büyük Ölçekli Haritalarda Diğer Ölçekler16Uyarı Notları19Bitişik veya Devam Eden Harita No’su20Diğer Notik Bilgiler13111615
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