Available Map Projections

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In ERDAS IMAGINE, map projection information appears in Projection Chooser, used to georeference images and to convert map coordinates from one type of projection to another. The Projection Chooser provides all of the supported map projections. The projections listed in the referenced topic are some of the commonly used projections.

See Map Projections for a list and descriptions of specific map projections.

Choice of the projection to be used depends upon the desired major property and the region to be mapped (see Projection Parameters Table). After choosing the desired map projection, several parameters are required for its definition (see Uses of Common Map Projections Table). These parameters fall into three general classes:

  • definition of the spheroid
  • definition of the surface viewing window
  • definition of scale

For each map projection, a menu of spheroids displays, along with appropriate prompts for specifying these parameters.

Units of Measure

Use the units of measure that are appropriate for the map projection type.

  • Geographic coordinates are expressed in decimal degrees. When prompted, you can use the DD function to convert coordinates in degrees, minutes, seconds format to decimal. For example, for 30°51’12’’:

dd(30,51,12) = 30.85333

-dd(30,51,12) = -30.85333

or

30:51:12 = 30.85333

You can also enter Geographic coordinates in radians.

  • State Plane coordinates are expressed in feet or meters.
  • All other coordinates are expressed in meters.

SHARED Tip Note also that values for longitude west of Greenwich, England, and values for latitude south of the equator are to be entered as negatives.

See Units of Measure in Help for definitions and formulas to convert units of measure for angles, distance, area, volume, and time.

Uses of Common Map Projections Table

Type

Map projection

Construction

Property

Use

0

Geographic

N/A

N/A

Data entry, spherical coordinates

1

Universal Transverse Mercator

Cylinder (see #9)

Conformal

Data entry, plane coordinates

2

State Plane

(see #4,7,9,20)

Conformal

Data entry, plane coordinates

3

Albers Conical Equal Area

Cone

Equivalent

Middle latitudes, E-W expanses

4

Lambert Conformal Conic

Cone

Conformal True Direction

Middle latitudes, E-W expanses flight (straight great circles)

5

Mercator

Cylinder

Conformal True Direction

Nonpolar regions, navigation (straight rhumb lines)

6

Polar Stereographic

Plane

Conformal

Polar regions

7

Polyconic

Cone

Compromise

N-S expanses

8

Equidistant Conic

Cone

Equidistant

Middle latitudes, E-W expanses

9

Transverse Mercator

Cylinder

Conformal

N-S expanses

10

Stereographic

Plane

Conformal

Hemispheres, continents

11

Lambert Azimuthal Equal Area

Plane

Equivalent

Square or round expanses

12

Azimuthal Equidistant

Plane

Equidistant

Polar regions, radio/seismic work (straight great circles)

13

Gnomonic

Plane

Compromise

Navigation, seismic work (straight great circles)

14

Orthographic

Plane

Compromise

Globes, pictorial

15

General Vertical Near-Side Perspective

Plane

Compromise

Hemispheres or less

16

Sinusoidal

Pseudo-Cylinder

Equivalent

N-S expanses or equatorial regions

17

Equirectangular

Cylinder

Compromise

City maps, computer plotting (simplistic)

18

Miller Cylindrical

Cylinder

Compromise

World maps

19

Van der Grinten I

N/A

Compromise

World maps

20

Oblique Mercator

Cylinder

Conformal

Oblique expanses (for example, Hawaiian islands), satellite tracking

21

Space Oblique Mercator

Cylinder

Conformal

Mapping of Landsat imagery

22

Modified Transverse Mercator

Cylinder

Conformal

Alaska

In Projection Parameters Table numbers are used for reference only and correspond to the numbers used in Uses of Common Map Projections Table. Parameters for definition of map projection types 0-2 are not applicable and are described in the text.

For Projection types 8, 20, and 21, additional parameters required for definition of the map projection are described in the text of Map Projections.

Projection Parameters Table

Projection type (#)

Parameter

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

Definition of Spheroid

Spheroid selections

Definition of Surface Viewing Window

False easting

False northing

Longitude of central meridian

Latitude of origin of projection

Longitude of center of projection

Latitude of center of projection

Latitude of first standard parallel

Latitude of second standard parallel

Latitude of true scale

Longitude below pole

Definition of Scale

Scale factor at central meridian

Height of perspective point above sphere

Scale factor at center of projection