<Dl> <Dd> x = 0.99 R λ y = 0.99 R ln ⁡ tan (π 4 + φ 2) k = 0.99 sec ⁡ φ . (\ displaystyle x = 0.99 R \ lambda \ qquad y = 0.99 R \ ln \ tan \! \ left ((\ frac (\ pi) (4)) + (\ frac (\ varphi) (2)) \ right) \ qquad k \; = 0.99 \ sec \ varphi .) </Dd> </Dl> <Dd> x = 0.99 R λ y = 0.99 R ln ⁡ tan (π 4 + φ 2) k = 0.99 sec ⁡ φ . (\ displaystyle x = 0.99 R \ lambda \ qquad y = 0.99 R \ ln \ tan \! \ left ((\ frac (\ pi) (4)) + (\ frac (\ varphi) (2)) \ right) \ qquad k \; = 0.99 \ sec \ varphi .) </Dd> <P> The scale on the equator is 0.99; the scale is k = 1 at a latitude of approximately ± 8 ° (the value of φ); the scale is k = 1.01 at a latitude of approximately ± 11.4 ° . Therefore, the projection has an accuracy of 1%, over a wider strip of 22 ° compared with the 16 ° of the normal (tangent) projection . This is a standard technique of extending the region over which a map projection has a given accuracy . </P> <P> When the Earth is modelled by an ellipsoid (of revolution) the Mercator projection must be modified if it is to remain conformal . The transformation equations and scale factor for the non-secant version are </P>

Why is mercator projection map still in use today