Flashcards in Mercator, Conical and Polar Projections Deck (17):

1

## 3 types of Mercator

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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

2

## Parallels of latitude on a Mercator

### Horizontal lines, unequally spaced

3

## What happens to scale on a Mercator

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Expands from the parallel of origin

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

4

## Parallel of origin of a conical chart

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

5

## Making the apex of the cone sharper and flatter

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

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

6

## Parallels of latitude on a conical

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Curved arcs of concentrated circles unequally spaced

7

## Meridians on a conical

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Straight lines converging at the poles

Equally spaced

8

## Convergence on a conical

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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)

9

##
Convergence factor is the same as

###
Sine of the parallel of origin

Constant of the cone ānā

360*/*in the chart = CF

10

## Constant scale

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Can be up to 1% error either side

11

## Lamberts conformal

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Cone cuts through the earth

2 standard parallels at east <= 16* apart

Increases the area of constant scale

12

## Scale on a lamberts conformal

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

13

## Rhomb and great circle lines on a conical

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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

14

## Convergence on a Polar

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=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

15

## Merdians on a polar

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Converge at a constant rate

Only true straight lines on this chart

16

## Rhomb lines and great circles on a polar

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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

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