Mercator, Conical and Polar Projections

Question 1

3 types of Mercator

Answer 1

Transverse - from the pole tangency

Direct - from the equator tangency

Oblique - tangency between the equator and the pole, used for countries that have a large N/S extent and limited E/W

Question 2

Parallels of latitude on a Mercator

Answer 2

Horizontal lines, unequally spaced

Question 3

What happens to scale on a Mercator

Answer 3

Expands from the parallel of origin

Expands with the secant of the latitude (1/cos lat)

Question 4

Parallel of origin of a conical chart

Answer 4

The circle of tangency would be a parallel of latitude - a small circle

Question 5

Making the apex of the cone sharper and flatter

Answer 5

Flatten the apex - parallel of origin would move upwards, towards the pole

Sharpen the apex - parallel of origin would move down, towards the equator

Question 6

Parallels of latitude on a conical

Answer 6

Curved arcs of concentrated circles unequally spaced

Question 7

Meridians on a conical

Answer 7

Straight lines converging at the poles

Equally spaced

Question 8

Convergence on a conical

Answer 8

It is the same throughout and does not depend on latitude
At the parallel of origin, earth convergency and chart convergency are the same

Convergency = CHlong x sine PO (conv factor)

Question 9

Convergence factor is the same as

Answer 9

Sine of the parallel of origin

Constant of the cone “n”

360/in the chart = CF

Question 10

Constant scale

Answer 10

Can be up to 1% error either side

Question 11

Lamberts conformal

Answer 11

Cone cuts through the earth

2 standard parallels at east <= 16* apart

Increases the area of constant scale

Question 12

Scale on a lamberts conformal

Answer 12

Scale is expanding outside the standard of parallels and contracting in between the 2 standard parallels

Question 13

Rhomb and great circle lines on a conical

Answer 13

Rhomb lines are curved, concave to the pole and convex to the equator

Great circles approximate to straight lines however, they have a small amount of curvature away from the parallel of origin

Question 14

Convergence on a Polar

Answer 14

=CHlong

As conversion factor = 1 (sine 90)

Anywhere on the chart, chart convergency is greater than earth convergency because EC from the pole (sine 90) to the equator (sine 0) = less than 1

Question 15

Merdians on a polar

Answer 15

Converge at a constant rate

Only true straight lines on this chart

Question 16

Rhomb lines and great circles on a polar

Answer 16

A great circle is slightly concave to the nearest pole and increases the concavity away from the pole but for practical uses we assume a straight line

A rhomb line is also concave to the pole but at a greater extent

Question 17

Formula for the scale expansion on a polar

Answer 17

Secant (squared) of the co-latitude/2