General Orthographic Map Help

All of the functions described within this page apply to all orthographic maps throughout the CLASS web site. Maps are created with the Generic Mapping Tools (GMT). Information on GMT can be found at: The GMT Home Page.

With the pan selection you can rotate the globe to any position you wish. This can be
done in any one of three ways. The first way is to simply click the mouse anywhere on the globe to center the globe where the mouse was clicked.

The second way is to use the rotation button just below the Pan selection. The globe
will rotate the amount of degrees selected, in the direction the rotate button was pressed.

The third method is to enter the Latitude/Longitude point in the text areas located
just under the Pan selection button. Once you have entered your values, press the "Redraw Map" button to center the map on that point.

Zoom

The zoom feature has two methods, "Zoom In", and "Zoom Out." To zoom in on the map, select the "Zoom In" button, and then click the mouse on the point on the map on which you wish to center and zoom. If you select "Zoom Out," you will zoom out, again centered on where you clicked the mouse.

The amount you zoom in or out on the globe is dependent on the zoom factor you have selected. This zoom factor will be multiplied upon itself each time you press the "Zoom" button. For example, if you have the default "2X" selected the first time you zoom in, you will have a zoom factor of 2. The next time you zoom in, the zoom factor would be 4. Each subsequent zoom would multiply the overall factor by 2.

Another feature of the zoom allows you to zoom onto an exact center point specified in the "Lat" and "Lon" boxes above. Simply press the "Redraw Map" button to zoom on the Lat/Lon center point selected. You may also modify the Lat/Lon center point manually as described in the Pan section.

Global

The global feature will zoom all the way out to a zoom factor of 1, centered on the Lat/Lon point specified. Select the "Global" button and then the "Redraw Map" button to zoom out to the entire globe.

Other General Features

Other general features of the Orthographic Map server include turning on and off Political Boundaries, Rivers, and the Digital Elevation Map (DEM).

The digital elevation map will create a relief map ranging from light green for low lying areas to red/brown for high terrain areas. This is a very slow feature, so use it sparingly. Currently, the resolution of the DEM data ranges from 120 km/pixel to 4 km/pixel, depending on how far zoomed in you are.

The "Grid Increment" feature allows you to select how many lat/lon degrees are between the grid lines. The selection of "AUTO" will fit the grid spacing depending on the amount you are zoomed in.