Applying a Map Projection

A map projection establishes the axis type and coordinate conversion mechanism for mapping points on the earth's surface, expressed in latitude and longitude, to points on a plane, according to one of several possible map projections.

You can apply a map projection before or after you import image or contour data into the iMap tool. To do so, select Operations →  Map Projection. This command opens the Map Projection dialog, shown in Figure 16-1.

Figure 16-1: The Map Projection Dialog

map_projection_dialog.gif

You can apply a map projection to another iTool as well. If you do, the tool will adapt to expose iMap functionality, including the iMap operations and the Map panel.

Table 16-1 shows the common projection properties.

Table 16-1: Common Map Projection Properties 

Name
Description

Description

Description of the map projection

Show dialog

Show this dialog before executing the Map Projection operation

Projection

Name of the map projection

Ellipsoid

Semimajor and -minor axes that define the ellipsoid

Semimajor axis

Length of the semimajor axis, in meters, for the reference ellipsoid

Semiminor axis

Length of the semiminor axis, in meters, for the reference ellipsoid

Center longitude (degrees)

Longitude in degrees of the projection's center

Center latitude (degrees)

Latitude in degrees of the projection's center

Longitude minimum (deg)

Minimum longitude to include in the projection, in degrees

Longitude maximum (deg)

Maximum longitude to include in the projection, in degrees

Latitude minimum (deg)

Minimum latitude to include in the projection, in degrees

Latitude maximum (deg)

Maximum latitude to include in the projection, in degrees

False easting (meters)

False easting to be added to each x-coordinate, in meters

False northing (meters)

False northing to be added to each y-coordinate, in meters

In addition to these properties, the following properties (Table 16-2) become available depending on the selected projection:

Table 16-2: Properties for Selected Map Projections 

Name
Description

Height (meters)

Height above surface, in meters, for satellite projections

Hemisphere

Hemisphere for UTM and Polar projections

HOM azimuth angle (deg)

Hotine Oblique Mercator azimuth angle (degrees) east

HOM latitude 1 (deg)

Hotine Oblique Mercator latitude, in degrees, of the first point

HOM latitude 2 (deg)

Hotine Oblique Mercator latitude, in degrees, of the second point

HOM longitude 1 (deg)

Hotine Oblique Mercator longitude, in degrees, of the first point

HOM longitude 2 (deg)

Hotine Oblique Mercator longitude, in degrees, of the second point

IS longitudinal zones

Intergerized Sinusoidal number of longitudinal zones

IS row justify flag

Integerized Sinusoidal flag that indicates what to do with rows with an odd number of columns. The following values are allowed:

  • 0 — Indicates the extra column is on the right of the projection y-axis
  • 1 — Indicates the extra column is on the left of the projection y-axis
  • 2 — Calculates an even number of columns

Mercator scale

Scale factor at the central meridian (for the Transverse Mercator projection) or the center of the projection (for the Hotine Oblique Mercator projection)

NAD27 Zone name (FIPS)

NAD27 State Plane Coordinate System Zone (FIPSZone)

NAD83 Zone name (FIPS)

NAD83 State Plane Coordinate System Zone (FIPSZone)

OEA horizontal shape m

Oblated equal area horizontal (m) shape parameter

OEA vertical shape n

Oblated equal area vertical (n) shape parameter

OEA rotation angle (deg)

Oblated equal area rotation angle, in degrees

SOM end-of-path flag

Space Oblique Mercator Landsat end-of-path flag, where 0 is the start and 1 is the end

SOM inclination (deg)

Space Oblique Mercator orbit inclination angle, in degrees, of the ascending node, counter-clockwise from the equator

SOM Landsat number

Space Oblique Mercator Landsat number (Worldwide Reference System)

SOM Landsat path

Space Oblique Mercator Landsat path number

SOM longitude (deg)

Space Oblique Mercator longitude, in degrees, of the ascending node

SOM period (minutes)

Space Oblique Mercator satellite period, in minutes

SOM ratio

Space Oblique Mercator Landsat ratio that compensates for confusion at the northern end of orbit

Standard parallel 1 (deg)

First standard parallel (degrees latitude) of true scale

Standard parallel 2 (deg)

Second standard parallel (degrees latitude) of true scale

Zone (1-60)

Universal Transverse Mercator (UTM) grid zone number (must be negative for zones in the southern hemisphere)

Note
The map projection properties are normally taken from the currently selected dataspace. However, in the Operations Browser, the map projection properties are registered on the operation itself. Changing these properties in the Operations Browser will have no affect on the currently selected dataspace. If the Show Dialog property is set to False and then the Map Projection operation is activated, the projection properties will be copied directly from the Map Projection operation onto the currently selected dataspace.

Note
Each projection has default longitude and latitude limits. If you have not modified one of these limits (the longitude and latitude minimum and maximum properties), the Map Projection operation will automatically use its default limit. However, if you have modified one of these limits, the Map Projection operation will use either your desired limit or the default limit, whichever is smaller.