Computing in Geographic Information Systems

Basics of Map Projection 71

= 2 tan

Φ

2

⇒ Φ = 2 tan

−1

y

4R

(4.55)

For orthographic projection we have h = ∞

y = R sin Φ

⇒ Φ = sin

−1

y

R

(4.56)

4.6 Conical Map Projection

Figure 4.5 shows that conic map projection has a lot of similarity to the

diagram and equations for cylindrical map projection. Therefore conical map

projection can be developed with slight modification and difference. The taper

of the cone is characterised by the ratio of its cross sectional radius to the

length of the slope from its apex. This ratio is constant for any distance from

the apex of a given cone and is called constant of the cone c given by the

equation

c = sinα (4.57)

where α is the