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Freud User Manual

CHAPTER 2 Map Background

Instantiating a map object
Basic map operations
Projections
Land and Ocean Display
Land outlines, fill, and visibility
Ocean fill
Grid
Map example

Instantiating a map object

Click on the map icon in the action panel. A new button will appear in the instance bar. The button labeled "Map-0" represents one instantiation of a map object (see Fig. 3).

Click on the button labeled "Map-0." A new window will appear (see Fig. 4). This window allows you to adjust parameters associated with this particular instantiation of a map.

Basic map operations

Move the mouse until the cursor is over the portion of the map window where the continents are displayed. Note that the Lat and Lon fields of the panel labeled Cursor change as you move the cursor; they indicate the current position of the cursor in map coordinates.

Move the cursor to a position somewhere over Alaska and press and hold down the SELECT button. A rectangular rubber band will appear that will track the position of the cursor relative to the first point in Alaska. Release the button when the cursor is over Florida. The rubber band now encloses the United States.

Go back to the base window and click on the Plot button. The drawing area of the base window will now contain a map of the United States.

The boundaries of the map can also be entered by hand. Just enter the desired bounds by entering the appropriate numbers in the Lat and Lon fields of the panels labeled Low and High. Click on the Plot button to see the new map.

Projections

Freud supports eight map projections-cylindrical equidistant, Mercator, north and south polar stereographic, north and south polar sector stereographic, satellite, and Mollweide. To select a projection, press and hold down MENU on the Projection button of the map window.

A projection menu will appear. Select the item labeled N. Polar Stereo from the menu by holding down the MENU button, moving the mouse until the cursor is over the item, and then releasing the button. The display area of the map window will be redrawn with the new projection (see Fig. 4).

Note that the rubber band in the map window has become an ellipse. Since this projection is centered on the pole, there is no need to specify an initial point for the rubber band; just hold down the SELECT button and move the cursor while it is over the map window to the desired boundary for the projection.

The satellite projection is slightly different. Select the Satellite item from the projection menu; you will see the display show in the figure (see Fig. 5).

The satellite view is determined by three parameters-latitude and longitude of the center of projection, and the distance in earth radii to the center of the earth. These values are set by adjusting the appropriate items in the Center and Distance fields above the map preview window. Try setting Lat to 90 and then click SELECT on the View button; you will see an updated view of the new projection. Note that rubber banding is not supported for this projection or the Mollweide projection.

As before, if you press the SELECT button on the mouse over the Plot button on the base window, a map with the chosen projection will be drawn in the display window.

Land and Ocean Display

Select the Land/Ocean item from the Properties menu. Note that the map window display changes to display three areas that are labeled Land, and Ocean fill,. The appearance of the the land and ocean areas of the map can be changed by these buttons. You can also use the keyboard to switch between the map coordinate window and the map extras window. Control+m is used to switch to the map coordinate window (the `m' stands for main), and control+e is used to switch to the land/ocean window.



Land outlines, fill, and visibility

Freud allows you to control the line style, line width, line color, fill pattern, and fill color of the land area of the map. Just select the desired item from the menus in the Land portion of the map extras window.

You can also choose to display continent outlines, or country outlines; the default is to show only continent outlines.

Ocean fill

The fill pattern and color of the world's oceans can be set by selected the appropriate menu item from the Stipple and Color menus in the Ocean portion of the map extras window.

Grid

You can change the appearance of the map grid by selecting Grid from the properties menu. This window allows you to:

Map example

Fig. 8 shows an example of two different map projections:.

Freud User Manual - 02 FEB 96
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