ZENITHAL GNOMONIC EQUATORIAL PROJECTION FOR THE CONTIENT SOUTH AMERICA AND AFRICA
EXERCISE :Prepare a graticule on the Gnomonic Equatorial Projection for the continent of South America at scale 1:150,000,000 and interval 10˚. INTRODUCTION: In gnomonic projection source of light is always in centre of the globe. The equatorial case of the projection is used to represent a hemisphere. The polar case is used to show the northern and southern hemispheres whereas the equatorial case is used to show the eastern and western hemispheres. CONSTRUCTION: Radious of the reduce earth is 250×10 6 /150× 10 6 = 1.66 // In the diagram - NESQ = the reduced globe EQ = The Equator NAES = The central meridian NOS = The axis of the Earth OE = The radious of the reduced globe. A = Any point on the Earth’s surface at ɸ˚ latitude along the central meridian B = Any point on the Earth’s surface at at θ latitude and θ longitude (Zero). C = Any point on the Earth’s surface at at ɸ˚ latitude and θ longitude TEP = Tangent plane at the equator.