2D Graphics Projection
The 2D Graphics Projection page enables you to control the display of the central body in the 2D Graphics window. You can:
- Define the projection format
- Display an Orthographic grid
- Select the center point for the map projection
If you click in the 2D Graphics window while the Projection page is open, STK applies any changes you've already set in any of the 2D Graphics properties pages.
Projection Format
Use the following to select and define the type of map projection to best support your analysis or simulation. (The parameters that you define depend on the projection type chosen.)
Type. The map projection type selected is saved when you save the scenario.
Azimuthal Equidistant. Projection is mathematically based on a plane tangent to the Earth. Spacing of the parallels is uniform.
Equidistant Cylindrical. Projection is mathematically based on a cone that is tangent at one parallel or conceptually secant at two parallels. North or south pole is represented by an arc.
Mercator. Projection can be thought of as being mathematically based on a cylinder tangent at the equator. Any straight line is a constant azimuth line, which is also called a loxodrome or rhumb line. The north and south poles can't be shown in this rectangular projection since they are at infinite distance.
Miller. Rectangular projection constructed to provide an alternative to the Mercator projection. The two projections are similar near the equator but the Miller projection avoids some of the exaggeration in scale near the poles.
Mollweide. Equal and pseudo-cylindrical projection showing the Earth in an ellipse with the equator twice as long as the map's actual meridian
Orthographic. Projection is geometrically based on a plane tangent to the Earth. The point of projection is at infinity. Directions from the center of the map projection are true. If you choose this projection type, you may need to define the display coordinate frame,display height, secondary body, and axes display. You may also want to display an orthographic grid.
Sinusoidal. Projection is mathematically based on a cylinder tangent on the equator. May have several central meridians.
Stereographic. Projection is geometrically projected onto a plane. The point of projection is on the surface of the sphere opposite the point of tangency. Directions from the center of the projection are true.
Perspective. Projection of the central body as a sphere from a user-specified viewing altitude. If you choose this projection type, you may need to define the display coordinate frame, field of view, secondary body, and axes display.
Hammer-Aitoff. Variation of the Lambert Azimuthal Equal Area projection that allows for viewing at both hemispheres simultaneously. The equal area characteristic of the Lambert projection is mostly preserved. This projection is visually similar to the Mollweide projection.
The fill properties for objects will only work when using Mercator, Equidistant Cylindrical, Miller, Mollweide, Sinusoidal, or Hammer-Aitoff projections.
ECF. Earth-Centered Fixed. The orbit track displays above the ground track over the entire span of displayed ephemeris.
ECI. Earth-Centered Inertial. A representation of the orbit in inertial space (corresponding to the current animation time) displays.
BBR. Body-to-body Rotating. If you choose BBR, use the Secondary Body option to select a secondary celestial body. This list may include asteroids and other celestial bodies in addition to the planets typically available in STK.
Display Height. If you select orthographic map projection, specify the height of the viewing plane. In all cases, the observer's position is fixed in the ECF reference frame at the Projection Center Position. If ECI is selected, the orbit plane appears to move in time as you animate.
Field Of View. If you select perspective map projection, specify an angle value to narrow or broaden the perspective. In all cases, the observer's position is fixed in the ECF reference frame at the Projection Center Position. If ECI is selected, the orbit plane appears to move in time as you animate.
Secondary Body. If you select orthographic or perspective map projection using a BBR display coordinate frame, use this option to select the secondary body that will be used as the frame of reference.
Show Axes. If you select orthographic or perspective map projection, turn ON the Show Axes option to show the X, Y, and Z axes for that view. To change the appearance of the axes in the 2D Graphics window, click Format... to display the Format Axes window, where you can define the display of individual axes.
Format button. Click to display the Format Axes window, where you can define the display of individual axes.
Orthographic Grid
If you selected the orthographic map projection, use the Orthographic Grid options to display a grid to assist in measuring distances (in kilometers) between locations in the 2D Graphics window. The following table outlines the options available for defining the display of an orthographic grid.
Show. Displays an orthographic grid in the 2D Graphics window.
Number of X Grid Line. If Show is enabled, indicate the number of X (horizontal) grid lines.
Number of Y Grid Line. By default, the number of Y (vertical) lines is the same as that set for X. If you wish to set a different number of Y lines to be drawn on the 2D Graphics window, turn on the Number of Y grid lines option and enter the value in the text box to the right of the option.
Color. If Show is enabled, select the color of the X and Y grid lines.
Center
Use the options in the Center area to select the center point for the map projection selected, enter the exact latitude and longitude degrees in the respective fields.
The Latitude field isn't available for Equidistant Cylindrical, Mercator, Miller, Mollweide, Sinusoidal, or Hammer-Aitoff projection types. The Altitude field is only applicable if you choose a Perspective map projection.
Aspect Ratio
The Always Keep 2:1 Aspect Ratio option, selected by default, preserves the 2 to 1 aspect ratio. Clear this selection if you want to stretch the map to fill the entire 2D Graphics window.
Tracking
Use the Cursor Position field to select the format you want to see displayed in the status bar for points on the map. You can select Lat/Long, UTM, or MGRS format.
Panning
The Enable mouse left-click and drag to pan map option is selected by default. This option enables you to pan left or right in the 2D Graphics window.